Diseases affecting gerbera cultivation and their control

Karmveer Kumar Gautam Susheel Kumar and Shri Krishna Raj

An International Journal of Floriculture Science and Landscaping 1The Journal of the Greens and Gardens Volume 03 No 05 06 amp 07 2020

An International Journal of Floriculture Science and LandscapingThe Journal of the Greens and Gardens Volume 03 No 05 06 amp 07 1-16 2020

Review Paper

Diseases affecting gerbera cultivation and their controlmeasuresKarmveer Kumar Gautam Susheel Kumar and Shri Krishna RajPlant Virology Laboratory CSIR-National Botanical Research Institute Rana Pratap Marg Lucknow-226001 (UP) IndiaCorresponding Author skraj2rediffmailcomSubmitted On July 15 2020Accepted On August 20 2020

Abstract

Gerbera (Gerbera jamesonii) is cultivated all over the world and is widely popular as an ornamental plant It isgrown in beds or pots and used as cut-flower in making bouquets and for decoration in ceremonial functionsAccording to the USDA NASS Census of Horticulture 2014 gerbera has a value of over $412 million dollarsannually It has been commercially cultivated by a large number of growers in India as a primary source of incometherefore has high socioeconomic impact in floriculture industry The area under gerbera cultivation in India isincreasing day by day due to its large scale uses and the market demands Gerbera production has been hampered bynumerous diseases that affect its flower quality and quantity Along with fungal bacterial and insect diseases viraland phytoplasma diseases causes considerable loss in gerbera cultivation and marketing In this review we describeabout disease symptoms virus and phytoplasma detection methods and identification of causal pathogens ofimportant viral diseases affecting gerbera production worldwide based on their biological serological and molecularcharacteristics and their effective disease management strategies

Key worlds Gerbera jamesonii virus diseases disease management virus-free plants virus resistant transgenicplants

INTRODUCTIONGerbera (Gerbera jamesonii) is a popular ornamental

plant of family Asteraceae named after Gerber a Germannaturalist It is native to South Africa and commonly knownas Barberton Daisy or African daisy The genus Gerberaconsists of about 40 species Out of the recorded speciesonly one species G jamesonii is under cultivation Subtropicaland Mediterranean climate is suitable for its growth and cutflower production around the world These climatic zonespass through Israel Italy Spain Portugal MoroccoColombia Japan South Africa Australia and Southern IndiaThe plants are stem-less tender and perennial herbs Theyare dwarf 30-45 cm tall amp hairy Leaves are leathery narrowerat the base and wider at the top and are arranged in rosetteat the base The flowers are daisy like 7-15 cm across Theflower may be single or double and available in various selfcolored cultivar as well as bicolor They are of wide rangecolors include yellow orange cream white pink red scarletsalmon maroon terracotta and various other intermediateshades It is considered as the fifth most used cut flower inthe world (after rose carnation chrysanthemum and tulip)(httpenwikipediaorgwikiGerbera) It has greatornamental value due to the typical capitulum inflorescence

that displays a great variety of colors and to the floral stemwhich is highly valued by consumers as individual vasedecorations and bouquet compositions (Mata et al 2009)Gerbera cultivars of commercial importance throughout theworld are Zingaro (red) Silvester (white) Salvadore(yellow) Rosaline (pink) Davaellen Goliath CreamClementine (creamy white) Maroon Clementine (orange)Flamingo (Pale rose) Delphi (white) Vista (red) Uranus(yellow) Fredenking (yellow) Terra queen (Pink) Dustty(red) Valentine (pink) Labalga (lilac) Fredaisy (pink)Fredorella (red) etc There are many other cultivars whichare cultivated commercially in India are Cream ClementineMaroon Clementine Delphi Vista Uranus TerraqueenDusty Valentine Diablo Mariso Pascal Winter Queen JaffaSangria Diana Paganini Rosetta Gloria Pricilla SunwayZingaro Balance Dune and Monique etc (httpsvikaspediainagriculturecropproductionpackage-of-practicesflowersgerbera-cultivation)

Gerbera is a very attractive commercial cut flower cropand marketed in the International floristsrsquo trade in hugequantities These plants are grown throughout the world ina wide range of climatic conditions The most importantproduction areas are the Netherlands Italy Germany

2 An International Journal of Floriculture Science and LandscapingThe Journal of the Greens and Gardens Volume 03 No 05 06 amp 07 2020

Diseases affecting gerbera cultivation and their control measures

France and California The Netherlands produces 420million stems of gerbera per year which is valued at 145million Netherlands guilders (Sudhagar 2013) Theproduction of gerbera was approximately US$ 220 millionin 2001 representing 70 million stems sold in US alone (Broeket al 2004) About 7 species were recorded in Indiadistributed in the temperate Himalayas from Kashmir toNepal at altitudes of 1300 to 3200 meters Gerberaproduction is maximum (2016 MT in 70 ha area) among theothers cultivated flowers such as carnation gladiolusmarigold rose tuberose in Uttrakhand Gerbera contributeswith a production of 17840 MT and stands fourth importantcut flower in India The total area of gerbera in India is 820ha with a cut flower production of 17 840 MT and looseflower of 3960 MT However maximum production ofgerbera comes from Uttarakhand (7 200 MT) whilemaximum area coverage is from Assam (600 ha) The shareof gerbera cut flower production in Karnataka is 200 MTand loose flower production is 580 MT (Anonymous 2015)According to DBT and Small Farmerrsquos AgribusinessConsortium India gerbera ranks as 2nd most domestic tissueculture flower crops in India after carnation anthuriumorchids in floriculture industry The cut flower sticks ofgerbera are been sold in market with the variable ratedepends on the flower quality and size According to recentsurvey of floriculture today gerbera farmers have recordedearnings of Rs 25000 - 30000- from an area of 134 sqmThe average income per unit area perhaps is the highest infloriculture ranging from Rs 100 to Rs 200 per sqmAccording to National Horticulture Board (NHB) of India2015-16 major gerbera producing states are Assam (1242Tones) Uttarakhand (514 Tones) Telangana (314 Tones)Karnataka (237 Tones) Meghalaya (092 Tones)Maharashtra (066 Tones) Tamil Nadu (052 Tones)Himachal Pradesh (030 Tones) Nagaland (004 Tones) andMizoram (003 Tones) Gerbera is grown commercially inIndia for export and domestic market In India we producevery high quality cut flower of the crop and millions of tissuecultured plants are produced Tropical Floritech Pvt Ltd inBangalore is the leading player in commercial cultivation inIndia (Chaudhary and Prasad 2000) The area under gerberacultivation in Karnataka is estimated at 25 ha withproduction of 53 lakhs cut flowers at an estimated value ofRs 15 lakh

PATHOGENS AND DISEASES AFFECTING GERBERACULTIVATION

Gerbera production is challenged by numerousdiseases caused by insect fungal bacterial nematodes viraland phytoplasma pathogens that affect its flower qualityand quantity The major pests (whitefly aphid leaf miner

thrips mites) diseases (powdery mildew collar rot root rotstem rot leaf spot) nematodes (root-knot spiral) and theirsymptoms biology spread and management have beendiscussed by Reddy 2016 The details of diseases caused byinsect fungal bacterial nematodes viral and phytoplasmapathogens are described as under

Insect-Pest DiseasesInsect-Pest incidence is the major factor responsible for

yield reduction in gerberas Gerberas have a wide variety ofpests such as aphids (Myzus persicae and Aphis jabae) (whichtransmit Cucumber mosaic virus and Potyviruses in nature)Leaf miner (Liriomyza trifolii and L soncho) Mites(Steneotarsonemus pallidus and Polyphagotarsonemus latus)Western flower thrips and caterpillars The whiteflies(Bemisia tabaci Genn Hemiptera Aleyrodidae) are majorpotential insect pests of greenhouse gerberas (Table 1)(Shalini et al 2019) These insect pests affect plant health bysucking of their sap as well as by transmitting many diseasesfrom infected to healthy plants

Nematode ProblemsAlthough a multitude of plant parasitic nematodes are

found associated with gerbera elsewhere in the world(Lamberti et al 1987) root knot nematodes belonging toMeloidogyne spp are predominant in India (Nagesh andParvath Reddy 2001) In India yield loss in gerbera due toMeloidogyne incognita was reported to be 311 (Nagesh andParvatha Reddy 2000) A survey was conducted in thedifferent districts of Tamil Nadu in the year of 2013 in orderto determine the most important plant parasitic nematodesspecies associated with gerbera The analysis of soil androot samples collected from the rhizosphere of gerbera ineach district revealed the presence of only five species ofplant parasitic nematodes These are Meloidogyne incognitaHelicotylenchus multicinctus Pratylenchus coffeaeTylenchorhynchus spp and Rotylenchulus reniformis Thepresent investigation revealed that M incognita is one of theserious limiting factors in commercial cultivation of gerberaunder polyhouse conditions present in Tamil Nadu (Manjuand Subramanian 2015) Nematodes also transmit somediseases caused by viruses such as Tomato bushy stunt virusand other Nepoviruses which also affect gerbera and otherplants grown in polyhouseglasshouse conditions

Fungal DiseasesGerberas have several fungal disease problems such

as root rots (by Pythium irregulare Rhizoctonia solani) crownand root rot (by Phytophthora cryptogea P drechsleri)Sclerotium rot (by Sclerotium rolfsii) Botrytis blight (by Botrytiscinerea) powdery mildews (by Erysiphe cichoracearum Oidium



crysiphoides) leaf spots (by Alternaria alternate) (Farhood andHadian 2012) (by Corynespora cassiicola) (Shi et al 2012)and by (Phyllosticta gerberae Alternaria spp) The downymildews yellow discoloration on leaf later turning light to

dark brown on gerberas are caused by Bremia luctucae(Wolcan et al 2010) and White rust (white erumpent sori) iscaused by Albugo tragopogonis (Vazquez et al 1997) Theoval circular or irregular brown to black lesions with

Table 1 Insect pest fungal bacterial and nematodes diseases on Gerbera and their disease managementInsect-Pest

Pest Managements (Reddy 2016) Whitefly (Trialewiodes vaporariorum) Spray Dimethoate (Rogor) Endosulphon (2 mll water) Aphids (Myzus persicae and Aphis jabae) Spray Dimethoate 2 mll of water Leaf Miner (Liriomyza trifolii and L soncho) Spray Chloropyriphos Diclorovous (Nuvan) (1 mll) Thrips Spray Rogor Nuvacron (2 mllitter) Mites (Steneotarsonemus pallidus) Spray Dicofol (Kelthane) Wettable Sulpher (15 gl) Catterpiller Apply Thimet (Phorete) 2 gplant apply around the base of the plant Western Flower Thrips Spray imidacloprid 04 mll followed by Pongamia or Neem oil 10 mll in case of severe incidence

Bacterial Diseases PathogenCause Disease amp Symptoms Management Reference Pseudomonas cichorii Bacterial Leaf Spot

Small to large spots are circular at first and then become irregular and dark brown to black May have a concentric ring pattern

Maintain low relative humidity Avoid overhead watering

Miller and Knauss 1973 Alivizatos 1986 Marques et al 2016

Nematodes Disease PathogenCause Disease amp Symptoms Management Reference Meloidogyne incognita Nematodes Root knot Stunting of plants

yellowing of leaves wilting of plants and heavy galling on roots

Pre plant treatment of beds with dazomet followed by the application of neem cake (1 kgm 2 15 days later) along with Paecilomyces lilacinus reduced populations of M incognita

Manju amp Subramanian 2015 Reddy 2016

Fungal Diseases PathogenCause Disease amp Symptoms Management Reference Alternaria Alternaria Leaf Spot

Brown specks form on florets and the leaf centers become white on the leaf spots

Maintain low relative Humidity and do not wet leaves when watering Apply Fungicides Dithane M-45 (Mancozeb) spray (15 glit) to protect the plants

Farhood and Hadian (2012) Shi et al (2012) and Reddy 2016

Botrytis cinerea Botrytis Blight Petioles have long brown spots Leaves turn yellow and die Petals have tan spots Stems at soil level are killed Infected tissues become covered with gray fungal growth

Space plants to insure good air circulation Maintain low humidity Avoid watering late in the day Remove crop debris Apply a fungicide to protect plants

Zhang 2006

Fusarium solani Fusarium Stem Rot Petiole of leaves blacken at the base as the plant collapses

Plant in pasteurized potting media Discard infected plants

Li et al 2008

Phytophthora cryptogea Phytophthora Crown Rot Plants wilt suddenly Leaves turn brown Roots are rotted and a crown rot develops

Plant in pasteurized potting media Avoid overhead watering Apply fungicide to protect plants

Martin et al 2014

Golovinomyces cichoracearum (formerly Erysiphe)

Powdery Mildew White fungal growth develops on the surface of leaves

Apply fungicide Aliette Topsin-M (2 glit) to protect plants

Wolcan et al 2010 and Troisi et al 2010

Pythium Pythium Root Rot Plants wilt and die as roots rot

Plant in pasteurized potting media Apply a fungicide Captan Benlate Aliette drench to soil (2 glit) to protect plants

Suzuki et al 2009

Rhizoctonia solani Rhizoctonia Crown Rot Stems at the soil level have a brown lesion Plants wilt and die

Plant in pasteurized media Apply a fungicide Wettable Sulphur spray (15 glit) to protect plants

Reddy 2016

Thielaviopsis basicola Thielaviopsis Root Rot Plants turn yellow wilt and die Roots are dark brown to black

Plant in pasteurized media Apply fungicide to protect plants

Reddy 2016



concentric rings on gerbera leaves are also reported to becaused by Alternaria spp (Mirkova and Konstantantinova2003) (Table1)

Bacterial DiseasesBacterial leaf spot disease on gerbera caused by

Pseudomonas cichorii also is reported The symptoms of thisdisease were small to large spots circular at first and thenbecame irregular and dark brown to black spots (Miller andKnauss 1973 Alivizatos 1986 Marques et al 2016) (Table1)

PHYTOPLASMA DISEASES OF GERBERAPhytoplasmas are intracellular obligate prokaryotes

which lack cell wall a pleiomorphic of filamentous shape adiameter less than 1 micro meter have a small genome andare mainly transmitted by leafhoppers They are associatedwith typical yellowing stunting of whole plant virescencephyllody proliferation of axillary buds witchesrsquo broom anddie back symptoms (Al-Saady and Khan 2006 Bertaccini2007 Harrison et al 2008) They are associated with severeyield losses in a variety of plant species of horticulturalagricultural and ornamental importance (Chaturvedi et al2010) Several lsquoCandidatus Phytoplasmarsquo taxon have beendescribed and specifications for novel species designationare based on less than 975 of 16S rDNA sequence identitywith that of previously described lsquoCa Phytoplasmarsquo taxon(IRPCM 2004)

Gerbera production are also reported to be affected byphytoplasma from different part of the world (Table 2) suchas Phytoplasma 16SrII from Australia and Phytoplasma16SrI from Italy (Siddique 2005) Candidatus Phytoplasmaasterisrsquo from Southern Italy (Spano et al 2011) andlsquoCandidatus Phytoplasma asterisrsquo (16SrI group) associatedwith yellows disease of gerbera from India (Gautam et al2015a) The details of gerbera diseases caused byphytoplasma have been described as under

Phyllody and green flower disease on gerberaIn 2005 A B M Siddique first time reported

phytoplasma association with gerbera phyllody in Australiabased on symptoms TEM study and molecular studyDuring a survey he observed the phyllody symptoms (greenflower) on gerbera plants in Central Queensland AustraliaLeaves and flowers from both symptomatic andasymptomatic healthy plants were examined by transmissionelectron microscopy (TEM) and the presence of pleomorphicbodies similar to phytoplasma was observed exclusively indiseased plants (Siddique 2005)

The presence of phytoplasma DNA in the infected

plants was also confirmed by Polymerase chain reaction(PCR) with phytoplasma specific primers Further DNAsequence analysis of the PCR product revealed highhomology with other phytoplasma DNA in the databaseBased on phylogenetic analysis of 16S rRNA the gerberaphyllody phytoplasma was grouped under Peanut witchesbroom as described by Lee et al 1998 The results of TEMPCR and sequencing analysis clearly indicated phytoplasmlassociation with phyllody disease of gerbera (Siddique2005)

Virescence and abnormal flower colour diseaseIn January 2010 Spanograve and coworker reported

lsquoCandidatus phytoplasma asterisrsquo infection in Gerberajamesoniim apulia from Southern Italy The infected plantshad phytoplasma like symptoms virescence phyllody andabnormal flower colour) and disease incidence was nearly100 in cv Maxima The phytoplasma infection wasdetected in total DNA extracted from the leaves of threesymptomatic by nested PCR with primers P1P7 (Schneideret al 1995) and R16F2R2 (Lee et al 1993) DNA fragmentsof 12 kb corresponding to 16S rDNA were amplified onlyfrom DNA of the three symptomatic samples The amplifiedfragments showed identical RFLP patterns which wereindistinguishable from those produced by the European asteryellows strain of the ldquoCandidatus Phytoplasma asterisrdquo(Spanograve et al 2011)

Further the 1803bp amplicon from P1P7 PCRamplification was cloned and sequenced (Accession NoJF795864) The ClustalW2 alignment confirmed that 16SrDNA of gerbera phytoplasma shared 999 identity withOenothera phytoplasma (accession No M30790 Lim andSears (1989) and 990 identity to several lsquoCa P asterisrsquoisolates of different ribosomal subgroups A B D E F Kand P Ca P asteris was widely spread in Italian cut flowercrops but this was the first report from gerbera in Apulia(Spanograve et al 2011)

Leaf yellows shortening and flower deformation diseaseIn India Gautam and co-worker first time reported

lsquoCandidatus Phytoplasma asterisrsquo (16SrI group) associatedwith yellows disease of gerbera (Gerbera jamesonii) in 2014The severe leaf yellows shortening of whole plant and flowerdeformation symptoms were observed on gerbera plantsgrowing in a polyhouse at Lucknow Uttar Pradesh India in2012 The disease incidence was about 15-20 and symptomsexhibited by the diseased gerbera were suggestive of thepresence of phytoplasma Total DNA was extracted fromleaf samples collected from symptom-bearing plants (Ahrensand Seemuumlller 1992) and PCRs were performed using P1



P6 universal primers (Deng and Hiruki 1991) followed bynested PCR using primers R16F2nR16R2 (Gundersen andLee 1996) Products of ~12 kb were amplified for four out offour samples from symptom-bearing plants but not from thesymptomless plants demonstrating the association of aphytoplasma with the disease (Gautam et al 2015a)

Amplicons from two samples Gerbera jamesonii yellowsphytoplasma (GYLu1) and Gerbera jamesonii yellowsphytoplasma (GYLu2) were cloned sequenced andsequence data was deposited under Accession NosJX674049 (GYLu1) and KC880350 (GYLu2) Sequencecomparison using BLASTn (httpblastncbinlmnihgovBlastcgi) revealed 99 homology between GYLu1 andGYLu2 GYLu1 and GYLu2 also shared 99 sequenceidentity with several strains of lsquoCandidatus Phytoplasmaasterisrsquo reported worldwide A similarity of 98 was verifiedbetween GYLu1 and GYLu2 when compared with thesequence of lsquoG jamesoniirsquo phytoplasma (JF795864) a memberof lsquoCa P asterisrsquo from Italy To find out phylogeneticrelationships of the gerbera phytoplasma strains under studyand 16S rDNA sequences of lsquoCa P asterisrsquo strains and otherphytoplasmas available in GenBank a phylogenetic tree wasgenerated using the neighbour-joining method The resultsdemonstrated that GYLu1 and GYLu2 clustered with thestrains of lsquoCa P asterisrsquo Based on high sequence identities(99) and close phylogenetic relationships with Italian

gerbera phytoplasma strain of lsquoCa P asterisrsquo the gerberaphytoplasmas from India were identified as lsquoCa P asterisrsquo-related strains (Gautam et al 2015a)

VIRAL DISEASES AFFECTING GERBERALike other viruses plant viruses are acellular

submicroscopic obligate parasite and made up ofnucleoprotein (DNA or RNA) Till date only RNA virusesare reported on gerbera which may be of two types single ordouble stranded The single stranded RNA viruses arefurther divided into two positive sense and negative senseIn gerbera mostly single stranded positive sense RNA[ss(+)RNA] viruses such as Impatiens necrotic spot virus (INSV)Tobacco mosaic virus (TMV) Tomato black ring virus (TBRV)Cucumber mosaic virus (CMV) Tobacco rattle virus (TRV) arereported but a very few report are of single stranded negativesense RNA viruses are reported and Tomato spotted wilt virus(TSWV) is one among them

Many viral diseases on gerbera are reported worldwideSome of them are Concentric rings and distortion of leavescaused by TSWV and Necrotic spot on leaf caused by TSWVand INSV are reported from Siberia (Stankovic et al 2011)and from New Zealand (Elliott et al 2009) respectivelyGerbera is also host for TMV and TBRV reported from China(Zhang et al 2009) Color break on the petals and deformedflowers on gerbera reported is due to infecting Cucumber mosaic

Table 2 Virus and phytoplasma diseases on Gerbera

Viruses and Phytoplasma Diseases Pathogen Natural Vector Symptoms Country References Tomato spotted wilt virus Western

flower thrips Concentric rings and distortion of leaves Serbia Stankovic et al 2011

Southern Italy Spano et al 2011 Venezuela Marys et al 2014

Chrysanthemum stem necrosis virus

Western flower thrips

Necrosis on leaf Slovenia Ranvikar et al 2003

Impatiens necrotic spot virus

Thrips Necrotic spot on leaf New Zealand Elliott et al 2009

Cucumber mosaic virus Aphids Mottled on leaf and distorted petals with colour break symptoms on flower

Australia Finlay 1975

Color break on the petals and deformed flowers India Verma et al 2004 Gautam et al 2017

Tobacco rattle virus Nematodes Ring spotting and light green line patterns on leaf Netherland Hakkaart 1967 USA Stouffer et al 1965 Germany Schmelzer et al 1966

Tomato black ring virus Black ring on leaf China Zang 2009 Tobacco mosaic virus Aphids and leafhoppers Mosaic on leaf China Zang 2009 Candidatus Phytoplasma Asterisrsquo

Leafhoppers

Virescence phyllody and abnormal flower colour Southern Italy Spano et al 2011

Candidatus Phytoplasma Asterisrsquo (16SrI group)

Leafhoppers Severe leaf yellows shortening of whole plant and flower deformation

India Gautam et al 2015

Virescence phyllody and abnormal flower colour Italy Bertaccini and Bellardi 1998 Ca Phytoplasma aurantifolia (16SrII)

Leafhoppers Phyllody symptoms (green flower) on Gerbera Australia Siddique et al 2005



virus on gerbera from India (Verma et al 2004a) Tobacco rattlevirus (TRV) are also reported on gerbera from Netherland(Schmelzer et al 1966 Stouffer et al1965) In 2002 SloveniaChrysanthemum stem necrosis virus (CSNV) was also detectedin gerbera The identity of CSNV was confirmed by ELISAand PCR (Ravnikar et al 2003) (Table 2)

Diseases Caused by Tomato Spotted Wilt Virus (TSWV)Tomato spotted wilt virus (TSWV) belongs to the

genus Tospovirus family Bunyaviridae is a sphericalnegative-sense RNA virus that has a diameter between 80-110nm TSWV is transmitted by thrips The western flowerthrips (Frankliniella occidentalis) is the vector thatpredominantly transmits TSWV globally and ingreenhouses TSWV infects over 1000 plant species andcauses significant economic damage to many agronomic andhorticultural corps In some areas the virus has been foundto be ubiquitous in the environment as it can infect manyweeds landscape plants and native plants Symptoms oftomato spotted wilt differ among hosts and can be variablein a single host species Stunting is a common symptom ofTSWV infection and is generally more severe when youngplants are infected Chlorotic or necrotic rings form on theleaves of many infected hosts

In May 2009 Stankoviaelig and co-worker first timereported TSWV on infected gerbera having chlorotic oak-leaf patterns followed by necrosis and distortion symptomsof leaves in green house of Vranjska Banja (Pegraveinj District) inSerbia based on disease incidence disease transmissionserological and molecular study During a surveyapproximately 30 gerbera plants were found to besymptomatic within a greenhouse Leaf sap of infectedgerbera were mechanically inoculated on healthyPetunia times hybrida resulted local necrotic spots symptoms onleaf suggested the presence of a Tospovirus For the serologicalstudy symptomatic leaves were tested for the presenceof TSWV by commercial double-antibody sandwich (DAS)-ELISA diagnostic kits (Loewe Biochemica SauerlachGermany) TSWV was detected serologically in 18 of 20gerbera samples The presence of TSWV in ELISA-positivesymptomatic gerbera plants was further confirmed byconventional reverse transcription (RT)-PCR Total RNAswere extracted with an RNeasy Plant Mini Kit and RT-PCRwas conducted with the One Step RT-PCR Kit (Qiagen) usingSerbian tobacco TSWV isolate (GQ279731) and RNA extractfrom healthy gerbera as positive and negative controlsrespectively Two different sets of TSWV-specific primersL1 TSWVRL2 TSWVF and M962M66 for a 276-bpfragment of the RNA-dependent RNA polymerase (RdRp)gene and a 897 bp fragment of the NSm gene respectively

were used for both amplification and sequencing RT-PCRanalyses of each tested plant detected the presence ofamplification fragments of expected size The amplifiedproducts corresponding to part of the RdRp and NSm genesderived from the isolate 158-Gerb were purified andsequenced in both directions (Accession Nos HQ246452 andHQ246453) Sequence analysis of the partial RdRp geneconducted using MEGA4 software revealed 911 to 98 ntidentity (951 to 988 amino acid [aa] identities) withcorresponding sequences of TSWV L RNA The highestidentity was found with an isolate from globe artichoke(AM940436) in Greece and isolates from tomato (GQ279732)impatiens (GQ132190) and tobacco isolates (GQ279731FJ189392 and FJ189393) found within Serbia Analysis ofthe NSm sequence of isolate 158-Gerb demonstratednucleotide identities varying between 906 and 996 (809and 996 aa identities) with those of previously reportedTSWV isolates The highest identity was with tobacco isolate(GQ373174) from Serbia This was the first report infectinggerbera in Serbia which may have a devastating influenceon its production (Stankoviaelig et al 2011)

In 2010 Spanol and co-worker reported of a resistancebreaking strain of Tomato spotted wilt virus (TSWV) from Gjamesonii Apulia in Southern Italy During survey they noticethat greenhouse-grown G jamesonii in Apulia were showingsevere malformations of die flowers and necrotic spots onthe leaves Estimated disease incidence in the gerbera plantsgrown in the greenhouse was 50 in cvs Sporza and Dune20 in cv Lancaster and 10 in cv Poseidon TSWV wasdetected in all samples tested by dot blot hybridization Twoviral isolates obtained from cvs Sporza were mechanicallyinoculated onto three plants each of tomato cvs UC82 FainoDiaz and Messapico the latter two carrying the Sw5resistance gene to TSWV Isolates Sporza and Dune but notthe local TSWV strain overcame the resistance and inducedsystemic necrosis Tomato cvs UC82 and Faino weresystemically infected by the two virus isolates These resultsshow that the TSWV isolates Sporza and Dune are of theresistance-breaking (RB) type (Ciuffo et al 2005) This wasthe first report of a RB strain of TSWV in gerbera in Italy(Spanol et al 2010)

In 2014 Marys and co-worker reported of Tomatospotted wilt virus (TSWV) on Gerbera in Venezuela based onsymptomatic plants showed concentric rings irregularchlorotic blotches and deformation on leaves Diseaseincidence was estimated at 30 Mechanical inoculationwith extracts of symptomatic leaves reproduced the typicalconcentric ring symptoms on indicator plants Arachishypogaea L cv San Martiacuten Capsicum chinense and Gjamesonii 6 to 15 days after inoculation In initial tests leaves



from each 30 symptomatic gerbera and chrysanthemumspecies from several greenhouse facilities in AltosMirandinos reacted positively when tested by DAS-ELISAwith polyclonal antisera raised against TSWV Total RNAwas extracted with the RNeasy Plant Mini kit (QIAGENHilden Germany) from two gerbera and two chrysanthemumELISA-positive samples The TSWV coat protein gene wasamplified by conventional RT-PCR using primers CP1 TSWV(TTAACTTACAGCTGCTTT) and CP2 TSWV(CAAAGCATATAAGAACTT) A single DNA product of~823 bp was amplified from all samples RT-PCR productswere directly sequenced (Accession Nos KF146700 andKF146701 derived from chrysanthemum KF146702 andKF146703 derived from gerbera) The resulting sequencesshowed over 99 identity with each other and were foundto be closely related (over 99) with TSWV isolates depositedin GenBank originating from different hosts from France(FR693058 FR693055) Montenegro (GU339506 GU339508GU355940) Italy (HQ830187) New Zealand (KC494501)South Korea (KC261967) and the United States (AY744476)This was the first confirmed report of TSWV infecting gerberaand chrysanthemum in Venezuela The relativelywidespread occurrence of TSWV in Miranda Stateunderscores the need for systematic surveys to assess itsincidence and impact on ornamental crops so thatappropriate management tactics can be developed (Marys etal 2014)

Diseases Caused by Cucumber Mosaic Virus (CMV)Cucumber mosaic virus (CMV) is the type member of genus

Cucumovirus in the family Bromoviridae It is reported to infect1287 plant species in 518 genera belonging to 100 families(Edwardson Christie 1987) worldwide The most commonsymptom induced by CMV is mosaic but the virus also causesfern leaf stunting of vegetable crops and malformation oftheir fruits It is transmitted by numerous species of aphidthrough the sap the seeds and dodder (Francki et al 1979Kaper and Waterworth 1981 Dijkstra and Khan 2006) CMVparticles are icosahedral in shape and 29 nm in diameter(Fig 1A) each consisting of 180 subunits of a single CP of~24 kDa and one of the genomic RNAs Based on their nucleicacid sequence similarity CMV strains can be divided broadlyinto two major subgroups (I and II) with subgroup I strainsdivided into two (A and B) subgroups The CMV genomecontains five genes expressed from either the three genomicRNAs or two subgenomic RNAs (Fig 1B) The 1a and 2aproteins are involved in virus replication whereas the 2bprotein is an RNA silencing suppressor an antagonist ofother host defense mechanisms The 3a protein and CP areessential for both cell-to-cell and long-distance movementprocesses Protein 2b and CP are expressed from subgenomic

RNAs designated RNA 4A and RNA 4 respectively RNA 4is packaged together with RNA 3 whereas the packagingarrangements for RNA 4A are not known except that it isonly packaged by subgroup II CMV strains CMV causessignificant losses to most of the major crops around theworld therefore are the bottlenecks to the crop production(Hull and Davies 1992 Valkonen 1998 Raj et al 2008)including gerbera (Gautam et al 2014)

In 1975 JR Finlay first time reported CMV on gerbera(Gerbera jamesonii Bolus) plants from two nurseries atBundaberg and from a home garden at Brisbane Australiabased on mottled on leaf and distorted petals with colourbreak symptoms on flower virus transmission bymechanically and by aphid Myzus persicae transmissionelectron microscopic (TEM) and serological study Duringtransmission study gerbera seedlings mechanicallyinoculated with the virus developed similar symptoms inthe systemically infected leaves but later growth was oftensymptomless The virus had-a host range similar to thatdescribed for CMV and was transmitted in a non-persistentmanner by the aphid Myzus persicae During the TEM studyPolyhedral particles 25 nm in diameter were observed innegatively stained preparations obtained from the sap ofinfected Nicotiana clevelandii by butanol clarification and twocycles of differential centrifugation The purified virus formeda single line of precipitation in gel diffusion tests against anantiserum to the Q strain of CMV a strain originally isolatedfrom capsicum in Queensland A distinct strain of CMV wasalso isolated from gerbera that was not transmitted by over150 M persicae in 6 tests and it rarely produced systemicinfection in cucumber Single joining precipitation linesformed in gel diffusion tests of this virus against itshomologous antiserum and antisera to the Q strain of CMVCalifornian cucurbit strain of CMV Queensland gladiolusstrain of CMV and the gerbera CMV strain describedpreviously CMV has not been recorded previously as the

Fig 1 Cucumber mosaic virus (A) Particle structure under TEMand their (B) Genome organization



cause of a disease in gerbera (Finlay J R 1975)

In 2004 Verma and co-worker first time reported CMVon gerbera (G jamesonii) in India based on virus transmissionenzyme-linked immune-sorbent assay (ELISA) TEM studyof virus particle and its molecular characteristics The CMVwas isolated from gerbera expressing color break on thepetals asymmetrical ray florets and deformed flowerssymptoms on gerbera growing in floriculture fields at theInstitute of Himalayan Bioresource Technology Palampurand nearby nurseries During host range or transmissionstudy the virus evoked chlorotic local lesions and systemicmosaic on many test species The virus was also transmittedin non-persist manner by Myzus persicae and Aphis gossypiiand was identified as CMV using ELISA with CMV-specificantibodies Polyhedral particles approximately 29nm wereobserved with electron microscopy of leaf dips fromsymptomatic gerbera leaves For molecular study total RNAwas isolated from the infected gerbera and N glutinosa plantCMV-specific primers were used to detect the virus withreverse transcription-polymerase chain reaction (RT-PCR)that produced an amplicon predicted size of 540 bpSequence alignment of the amplicons by BLAST resulted in91 to 99 homology with the partial inter cistronic regionand partial coat protein gene (1042-1574 bp) This genesequence was submitted to GenBank database (Accessionno AJ634532) as RNA3 of CMV subgroup I The naturaloccurrence of CMV on gerbera is reported earlier fromAustralia India and China This was the only report fromIndia describing the CMV by ELISA and analysis of a smallsequence amplified by RT-PCR from gerbera exhibitingcolour break symptoms on petals asymmetrical ray floretsand deformed flowers (Verma et al 2004)

In 2014 Gautam and co-worker reported CMV onGerbera (G jamesonii) based on complete RNA3 genomesequences associated with severe chlorotic mosaic andflower deformation disease in two cultivars (Zingaro andSilvester) growing in a polyhouse at CSIR-NBRI LucknowIndia (Fig 2) The disease incidence was 1627 in cvZingaro followed by 1157 in cv Silvester The transmissionof causal virus was attempted using the leaf sap of naturallyinfected gerbera (G jamesonii) plants of cultivars (cvs)Zingaro and Silvester separately on some recipient hostseedlings During sap transmission tests the virus wassuccessfully transmitted from naturally infected gerbera tohealthy gerbera seedlings which developed similar chloroticmosaic symptoms at 40-45 dpi suggesting the Kochrsquospostulates The inoculations of sap taken from cultivarsZingaro and Silvester also induced more or less similar localand necrotic lesions and systemic mosaic symptoms on Csativus C annuum P hybrida N glutinosa N tabaccum cv

White Burley and N rustica at 30-35 dpi For moleculardetection of the virus the total RNA was extracted from 100mg leaf tissue of symptomatic plants of gerbera cv Zingaroand Silvester using TRIzol (Sigma USA) and reversetranscription-polymerase chain reaction (RT-PCR) wasperformed using CMV-CP gene specific primersElectrophoresis of RT-PCR products resulted inamplification of expected size ~650 bp bands in naturallyinfected gerbera samples of cv Zingaro and Silverster similarto as in CMV-Banana strain taken as positive controlconfirming the presence of CMV Further the complete RNA3genome of CMV was amplified by RT-PCR using CMV-RNA3primer from three infected gerbera leaf samples Theamplicons obtained were cloned sequenced and depositedin GenBank under the accessions JN692495 JX913531 (fromcv Zingaro) and JX888093 (from cv Silvester) Thesesequences shared 98-99 identities to each other and witha strain of CMV-Banana reported from India and 90-95 identities with various strains of CMV reported worldwidePhylogenetic analysis revealed their closest affinity withCMV-Banana strain and close relationships with severalother strains of CMV of subgroup IB This study providedevidence of subgroup IB CMV causing severe chlorosis andflower deformation in two cultivars (Zingaro and Silvester)of G jamesonii in India (Gautam et al 2017)

Diseases Caused by Tobacco Rattle Virus (TRV)Tobacco rattle virus (TRV) is an important plant

pathogenic virus of family Virgaviridae Genus Tobravirus Itis transmitted by nematodes of the genera Trichodorus and

Fig2 A view of naturally infected gerbera plants exhibitingchlorotic mosaic symptom in polyhouse conditions (a) a closeview of infected leaf showing severe chlorotic mosaic andgreening of vein symptoms (b) and severe color breaking andflower deformation symptoms (c) as compared to healthy flower(d)



Paratrichodorus (Fauquet et al 2005) It can also bemechanically and seed transmitted It has a linear single-stranded positive-sense RNA divided into two segmentsRNA 1 (6791 nt) and RNA 2 (1905 nt) Its particles are tubularwith helical symmetry 23 nm in diameter Over 400 speciesof plants from 50 families of vegetables ornamentals andweed are susceptible to infection It causes the disease corkyringspot in potatoes

The occurrence of TRV in gerbera has been reported byStouffer (1965) who found it in field-grown plants in theUSA and by Schmelzer (1966) in the German DemocraticRepublic In 1967 Hakkaart FA received some gerbera plantswith virus like symptoms from a commercial grower in TheNetherlands The leaves showed ring spots and light greenline patterns which in older leaves often became necroticSap from affected leaves was inoculated on several plantspecies Three of these Nicotiana tabacum lsquoWhite BurleyrsquoChenopodium amaranticolor and Datura stramonium developedsymptoms typical for TRV Inoculation of healthy gerberaseedlings with sap from the infected N tabacum caused linepatterns and ring spots and the virus could be re-isolatedfrom these plants This was the first time that TRV has beendetected in gerbera in The Netherlands (Hakkaart 1967) Itis unlikely that the disease will become of economicimportance in The Netherlands since soil steaming beforethe beginning of the culture is already common practice as ameasure of control of foot rot caused by fungus species

Diseases Caused by Impatiens Necrotic Spot Virus (INSV)Impatiens necrotic spot virus (INSV) of family

Tospoviridae genus Orthotospovirus is an economicallyimportant pathogen in a broad host range of ornamentalplants INSV is easily mechanically transmissible oftencauses severe damage on infected plants and spread rapidlythrough insect vector (Thysanopthera) INSV has beenreported to infect more than 300 plant species Stuntingringspots brown to purple spots on leaves or stems stembrowning (cankers) flower breaking symptoms may bepresent on a plant infected with INSV

INSV was first detected in New Zealand in August2003 in Freesia refracta plants growing in a nursery on theSouth Island of New Zealand However in June 2006 abegonia (Begonia times tuberhybrida) specimen from a fourthNorth Island nursery was received which was found to beinfected with INSV Other species confirmed by RT-PCR tobe infected at this site include cyclamen (Cyclamen persicum)gardenia (Gardenia jasminoides) gerbera (Gerbera jamesonii)as well as hibiscus (Hibiscus rosa-sinensis) These hosts wereconsidered as the new hosts for INSV Partial nucleotidesequences obtained by RT-PCR were found to be closely

related to the published sequences (Elliott et al 2009)

MANAGEMENTS OF GERBERA DISEASESThe management of diseases caused by insect pests

fungal bacterial nematode phytoplasma and various viralpathogens in gerbera are being described in details below

Management of Insect-Pest Infecting GerberaGerbera infecting insect-pest may be controlled by

insecticides such as Dimethoate (Rogor) Endosulphon(2mlLitter water) for Whitefly Chloropyriphos Diclorovous(Nuvan) (1 mllitter) for Leaf Miner Rogor Nuvacron (2mllitter) for Thrips Dicofol (Kelthane) Wettable Sulpher (15glitter) for Mites and Thimet (Phorete) 2gplant may be appliedaround the base of the plant for leaf eating caterpillar etc(Table 1)

Fungal Bacterial and Nematodes Disease ManagementCommon fungal diseases infecting gerbera can be

controlled by fungicides such as Captan Benlate Aliettedrench to soil (2glit) for Root rot Aliette Topsin-M (2 glit)for Powdery mildew Wettable Sulphur spray (15glit) forCrown rot Dithane M-45 (Mancozeb) spray (15glit) forAlternaria leaf spot (httpsccariresingerberapdf) Whilebacterial diseases may be controlled by spraying of antibioticsuch as streptocycline at 02 gl or Kasugamycin at 125mll (Table 1)

Phtoplasma Disease ManagementControl of epidemic outbreak of phytoplasma diseases

can be done either by controlling the vector or by eliminatingthe pathogen from the infected plants by meristem tip cultureantibiotics or other chemical such as tetracycline etc(Bertaccini 2007 Chaturvedi et al 2010) Since gerbera ispropagated through vegetative means and massmultiplication through tissue culture Gautam et al 2015asuggested detection of phytoplasma in gerbera at early stagesof its development and removal of infected plants from thecultivated field may be the most importance tool fordevelopment of its disease management practices

It is well known that the only antimicrobials being usedto control phytoplasmas are tetracycline-class antibioticsRecently Tanno et al 2018 performed the comprehensivescreening of antimicrobials to control phytoplasma diseasesusing an in vitro plant-phytoplasma co-culture system anddeveloped an accurate and efficient screening method toevaluate the effects of antimicrobials In this study they tested40 antimicrobials in addition to tetracycline and four ofthese (Doxycycline Chloramphenicol Thiamphenicol andRifampicin) decreased the accumulation of lsquoCandidatus (Ca)



Phytoplasma asterisrsquo The phytoplasma was eliminated frominfected plants by the application of both Tetracycline andRifampicin (Tanno et al 2018)

Management of Viral DiseasesManagement of viral diseases is much more difficult

than that of diseases caused by other pathogens (Verma etal 2002) because of the viral diseases have a complex diseasecycle efficient vector transmission and no effective virucidesavailable Integration of various approaches like theavoidance of sources of infection control of vectors culturalpractices (conventional) and use of resistant host plants (nonconventional) have been used for the management of diseasescaused by plant viruses (Fig 3)

Remove all plant debris as well as weeds and floweringplants growing nearby production areas as these can besources of new infections and infestations It was suggestedthat soil sterilization can also eliminate the developmentalstages of vector species (Elizabeth et al 2016)

Biological Controls - Biological controls can be effective forcontrolling of Thrips species when their populations are lowSome predator species have been identified for control ofwestern flower thrips These are Euseius stipulatusMetaseiulus occidentalis (Nesbitt) Amblyseius andersoni (Chant)Amblyseius scutalis (Athias-Henriot) and Amblyseius (Euseius)tularensis (Congdon) (Elizabeth et al 2016)

Lady beetles (Coleoptera Coccinellidae) ladybugs orladybird beetles are among the most visible and best knownbeneficial predatory insects Over 450 species are found inNorth America Most lady beetles in North America arebeneficial as both adults and larvae feeding primarily onaphids They also feed on mites small insects and insecteggs (httpsbiocontrolentomologycornelledupredatorsladybeetlesphp)

Fig 3 Summary of management of viruses infecting Gerbera(based on literature by Korbin 2002 Zang 2009 Gautam et al2017 and Elizzabet et al 20016)

By Cultural Practices - Prevention is the key for managingTospovirus diseases because Tospovirus-infected plantscannot be cured If viral infection is suspected in gerberaplants samples should be sent to testing facilities to confirmthe presence of the virus Once the disease has beenidentified the only management option is to discard infectedplants (Whipker 2014) However managing the vector ofthe virus the spread of western flower thrips can beminimized This can be done using strategies to physicallyexclude the pests such as installing fine mesh screens (meshsize lt135 nm) on external openings to prevent entry of thripsvectors into the greenhouse Monitoring using indicatorplants such as petunia or sticky cards can be helpful toprovide early warnings of the presence of F occidentalis (Allenand Matteoni 1991)

By Sanitation - It is well kwon fact that sanitation of thecultivation fields enhances crop production by many folds

Fig 4 Different regeneration stages in the development of virus-free plants Floral bud showing callus initiation after one month(a-b) shoot proliferation (c-d) after 60 day on MS mediumsupplemented with BA (10 mgl) IAA (05 mgl) and Ads (05mgl) hormones rooting of shootlets in Gerbera rooting mediaafter 20 days (e) hardening of plants at culture room conditionsfor one week (f) and in glasshouse condition (g) A panoramicview of glasshouse grown virus-free gerbera cv Zingaro plantsin comparison with CMV infected gerbera plants at bloomingstage (h)



Biological control of aphid vectors of CMV by ladybird(Coceinella transversalis) has also been studied by Kumar 2009during the Ph D dissertation The biological control of aphidvectors population (capable of transmitting CMV and TAVand potyviruses in several plant species) has been attemptedby ladybird (C transversalis) a predator of aphids The feedingbehavior of C transversalis has been observed onchrysanthemums Different larval stages as well as adultlady bird predators have been explored for minimizing aphidpopulation The larval stage is found to be most efficient forfeeding of aphid population as compared to adults (Fig 5) Itfeeds approximately 20 aphids per minute It was alsoobserved that aphids quickly migrate from the ladybirdsThese observations may be utilized for minimizing the aphidpopulation indirectly minimizing the load of the virus innature (Kumar 2009) It is suggested that such eco-friendlyapproaches of virus-disease management are needed to bedeveloped which neither has adverse effect on human healthnor possesses hazards to the environment

better crop production yield (Agrios 1978)

Literature survey revealed the only record of a postgraduated dissertation by Zhang 2009 who attempteddevelopment of virus-free plants of G jamesonii cv Bolus formanagement of four viruses TBRV TMV CMV and TRVHe inoculated these viruses on G jamesonii and used its threedifferent explants (tip leaf and torus) for their eliminationthrough heat treatment followed by in-vitro tissue cultureHe found that tip and torus culturing was the best methodfor obtaining virus-free gerbera plants He verified the virus-free plants by multiplex RT-PCR and real-time RT-PCR andfound that the rates of virus-free by tip cultures were 750and 667 respectively while rates were 520 and 545respectively by torus cultures In this study the highest 750and 545 virus-free gerbera plants were obtain by tip cultureand torus culture respectively in combination ofthermotherapy The success of virus-free for G jamesoniiBolus by tip culture and torus culture was the first reportfrom China (Zhang 2009)

Then after Gautam and co-workers in 2017 attemptedsuccessful elimination of CMV through in vitro chemotherapy(using 30 mgL virazole) of ~4 x 8 mmsup2 capitulum explantsof infected gerbera cv Zingaro for its quality improvementA total of 38 plants were developed from 57 explants onMurashige and Skoog (MS) medium supplemented with 1mgL 6-benzylaminopurine (BAP) 05 mgL indole-3-aceticacid (IAA) and 05 mgL adenine sulphate (Fig 4) Thedeveloped plants showed absence of CMV in 816 (3138)plants when screened by RT-PCR using coat protein specificprimers of CMV The CMV-free plants showed better plantgrowth increase of 537 in length of leaf lamina and 592in leaf width as well as better blooming performance increaseof 626 in flower size (diameter in cm) and 691 in numberof flowers per pot having intense red flower colour ascompared to the control ones Elimination of CMV by in vitrochemotherapy (using virazole) of capitulum explants ofgerbera cv Zingaro is being reported for the first time fromIndia (Gautam et al 2017)

Development of Virus Resistance Transgenic Gerbera -Pathogen-derived resistance has been observed to bemediated either by the protein encoded by the transgene(protein-mediated) or by the transcript produced from thetransgene (RNA-mediated) also known as posttranscriptional gene silencing (PTGS) or both (Varma et al2002) In Literature several virus resistance transgenic plantshave been develop in various plants but in gerbera firstreported from Poland for TSWV (Korbin et al 2002) and thenafter from India for CMV (Gautam et al 2019)

Fig 5 Aphid feeding by ladybird (C transversalis) in its adult (Aamp B) and larvae (C amp D) stage on Chrysanthemum (A) Tobacco(B) and Dahlia plants (C amp D)

Predation has immediate consequences for prey fitnessand early assessment of predation risk may be advantageousfor prey Ninkovic et al 2013 investigated the ability of thebird cherry-oat aphid Rhopalosiphum padi to detect one ofits important predators seven spot ladybird Coccinellaseptempunctata via chemicals in the predatorrsquos walking trackThis avoidance mechanism may play an important role inthe biological control exerted by predatory ladybirds onaphid populations (Ninkovic et al 2013)

Use of Virus-free Gerbera Planting Material - Virusesspread from mother plant to their progenies through infectedcuttings tubers and other vegetative plant materials thathave great possibility of virus transmission Use of virus-free planting material and their transplantation ingreenhouses that isolates crop from other plants whichharbor or may harbor viral diseases has been suggested for



Nucleoprotein Gene Based Viral Resistance for TomatoSpotted Wilt Virus (TSWV)

Nucleoprotein gene based viral resistance in G hybridcv Princersquo lsquoPaulrsquo lsquoAlaskarsquo and lsquoZuzanna for Tomato spottedwilt virus (TSWV) has been developed by Korbin and co-worker (Korbin et al 2002 and Korbin 2006) Theysuccessfully introduced resistance to TSWV usingAgrobacterium-mediated transformation They integrated aresistance-related nucleoprotein gene from the virus intoGerbera explants and found that these transgenic plants diddemonstrate resistance when mechanically inoculated Theyused shoots bases of shoot clumps and leaf explants rootinghormones TDZ = 1-15 IAA = 02-05 and Kinetin = 1 IAA =02-05IAA = 5 (mgl) Agrobacterum strain LBA 4404harboring pBin19 plasmid and cefotaxime and Kanamycin250 and 70 (mgl) for genetic transformation Resultedtransformation efficiency was 54 and transgenic plantsdid demonstrate resistance when mechanically inoculatedby TSWV (Korbin et al 2002)

Plants of four gerbera cultivars were transformed withnucleocapsid N-gene of Tomato spotted wilt virus wereevaluated in terms of resistance to the virus and severalphenotypical traits Sixteen out of 33 transformed genotypes(transgenic plants) were confirmed by PCR with specificprimers for N and npt II genes After mechanical inoculationwith TSWV typical symptoms of viral infection appeared inthe control plants after two to four weeks but no diseasesymptoms were observed in any of the infected transgenicplants Assessment of other phenotypical traits of gerberaconfirmed lack of significant differences betweentransformed and control plants Except for one genotype oflsquoPrincersquo and one genotype of lsquoZuzannarsquo all of thetransformed plants can be potentially good breeding material(Korbin 2006)

Coat Protein Based Viral Resistance in Gerbera forCucumber Mosaic Virus (CMV)

Keeping in view of trait improvement and developmentof in built resistance against viruses in gerbera Gautam andco-worker attempted the genetic transformation using CMV-CP gene and leaf petiole and petiole base explants of gerberaWhen differentiate hormones combination were added toMS basal medium base petiole of explant has shown higherregeneration efficiency as compared to petiole and leafexplants The 7-25 mgl concentrations of Kanamycin wereused in this study for Agrobacterium mediated transformationof base petiole explants of gerbera The use of 15 mglconcentration of Kanamycin was found optimum duringtransformation experiments

Conclusively a total of 310 base petiole explants ofgerbera cv Zingaro were co-cultivated for transformationOut of them 97 explants were successfully regenerated onselection medium All shoots were transferred to rootingmedium where 52 plants had developed a well organizedbranched root system The developed transgenic plants wereplaced under greenhouse conditions for acclimatization fromwhere the survived 88 plants were chosen for molecularvalidation The results of PCR Southern and Northern blotanalysis confirmed that total 89 plants had CP geneintegration in their genome The transgenic plants whenchallenged with leaf sap inoculums of CMV The resultsshowed virus resistance in 53 and virus tolerance (delayedand mild symptoms) in 33 plants while rest of the plantshowed severe disease symptoms for virus infection afterchallenged with mechanical inoculation of CMV Thedeveloped protocol may be adopted for transferring any othergene of agronomic or economic interest in gerbera plants(Gautam et al 2019 unpublished data submitted to IJEB)

Development Quick and Reliable Virus DiagnosticProtocols for Gerbera Viruses

The development quick and reliable virus diagnosticprotocols for detection of viruses in gerbera were prerequisitefor indexing of gerbera materials in bulk and to identifyvirusdisease free materials to be used for large scale gerberapropagation and its mass multiplication through tissueculture industry In this direction Gautam 2015b attemptedfor standardization and development of two protocolsWestern blot immunoassay and RT-PCR using antiserum ofCMV and CMV specific primers respectively for successfuldetection of Cucumber mosaic virus (CMV) in two varieties ofgerbera being cultivated in India

Western blot immunoassay for CMV detection ingerbera was developed by (Gautam 2015b) Duringserological detection by western blot immunoassay the crudeprotein preparations from naturally infected gerbera cvsZingaro and Silvester samples reacted positively with theantiserum of CMV (PVAS242a ATCC USA) raised againstthe capsid protein and showed two bands of 26 and 52 kDasimilar as in case of CMV-Banana (Vishnoi 2012) taken aspositive control (Fig 6) however no such band was observedin a sample of healthy gerbera The 26 kDa band was of coatprotein of CMV and 52 kDa band seems to be a dimmer of 26kDa protein as reported in case of many CMV strains(Francki et al 1979 Raj et al 1997) These results of westernblot immunoassay indicated the CMV infection in Gerberaplants (Gautam 2015b)



Molecular detection of Cucumber mosaic virus isolatesin gerbera by RT-PCR was also developed by (Gautam2015b) The RT-PCR performed with CMV-CP gene specificprimers resulted in amplification of expected size ~650 bpbands in naturally infected gerbera samples of cvs Zingaroand Silverster which was similar as in CMV-Banana infectedsample taken as positive control (Fig 26) The sap inoculatedgerbera (cvs Zingaro and Silvester) C sativus and N tabaccumcv White Burley plants also showed the ~650 bp ampliconwhen tested by RT-PCR (Fig 7) confirming the presence ofCMV in sap inoculated plants (Gautam 2015b)

tissues with TBRV TMV CMV and TSWV respectively (Zanget al 2009)

CONCLUSIONSG jamesonii is an important commercial ornamental

plant Its popularity increases day by day worldwide InIndia gerbera industry suppose to be sunrise industry inexport point of view It takes important role in India as wellas world economy However several factor responsible forbottleneck of gerbera production Insect-pest fungal bacteriaphytoplasma and viruses have important role Control ofinsect fungal bacteria and phytoplasma pathogens can bedone using insecticide fungicide and antibiotic etc Thecontrol of gerbera plant viruses is slightly difficult becauseof non availability of effective viricide for viruses Howeverseveral conventional and non conventional methods vizsanitation bio-control development of virus-free plants andtransgenic gerbera plants are available for effectivemanagement of gerbera viruses Present review particularlyfocuses on disease symptoms of infected gerbera as well asbiological serological and molecular detection of viruses andphytoplasma infecting gerbera worldwide This reviewindicated that viruses until reported on gerbera have singlestranded RNA genome Therefore RNA based pathogenderived resistance against gerbera viruses would be usefulfor gerbera virus management The protocol developed forelimination of CMV and production of virus-free elitevarieties of gerbera cv Zingaro plants may be utilized tosave the germplasm from virus infection The technique mayalso be used for the mass propagation of virus-free elitevarieties of gerbera which may of importance to thefloriculture industry

This information summarized in this review will beuseful for gerbera growers worldwide that ultimately wouldbenefit in uplifting the economic and social status of thegerbera related farmers Moreover an eco-friendly approachlike biological control of virus transmitting vectors in naturehas also been suggested for virus-disease managementwhich neither has adverse effect on human health norpossesses hazards to the environment The developeddiagnostic protocols may be used for quick and reliabledetection of viruses in gerbera and for indexing of gerberamaterials in bulk and to identify virusdisease free materialsto be used for large scale gerbera propagation for farmersand its mass multiplication through tissue culture industry

ACKNOWLEDGEMENTSThanks are due to the Director CSIR-NBRI Lucknow

India for necessary lab facilities K K Gautam is thankful toIndian Council of Medical Research (ICMR) New Delhi for

Fig 6 Western blot immunoassay using CMV-CP antiserumshowing 26 and 52 kDa bands in naturally infected gerbera cvsZingaro and Silvester samples (lane 1- 2) confirming CMVinfection as compared to CMV-Banana (P) positive control LaneH is healthy gerbera

Zang and coworkers in 2009 developed multiplex RT-PCR for detecting Tomato black ring virus (TBRV) Tobaccomosaic virus (TMV) and Cucumber mosaic virus (CMV)simultaneously for detecting Tomato spotted wilt virus(TSWV) Tobacco rattle virus (TRV) and Tobacco mosaic virus(TMV) and real-time RT-PCR for detecting 4 viruses TBRVTMV CMV and TSWV respectively from G jamesonii BolusThe multiplex RT-PCR for detecting TBRV TMV and CMVcould detect as low as 1igraveg the three leaf tissues While themultiplex RT-PCR for detecting TSWV TRV and TMV coulddetect as low as 1mg the three leaf tissues The real-time RT-PCR could detect as low as 1ng 1ng 100pg and 1igraveg the leaf

Fig 7 RT-PCR amplification of CP gene from naturally infectedand sap inoculated plants using CMV-CP gene specific primersconfirming CMV infection Lanes PC = CMV-Banana infectedtobacco plant (as positive control) NC = healthy gerbera plants(as negative control) 1-4 = infected gerbera samples 5-8 sap-inoculated test plants of N tabacum cv White Burley N glutinosaN rustica and C sativus M = DNA marker



fellowships Thanks are also due to Dr R K Roy the HeadBotanic Garden and Floriculture Department CSIR-NBRILucknow for providing Gerbera samples This study wasfunded by the In-house project OLP-105 CSIR-NBRI

REFERENCESAgrios GN 2005 Plant Pathology 5th Edn Elsevier Academic

Press Burlington Mass p 952Ahrens U Seemuller E 1992 Detection of DNA of plant pathogenic

mycoplasma-like organisms by a polymerase chainreaction that amplifies a sequence of the 16S rRNA genePhytopathology 82 828-832

Alivizatos SA 1986 Pseudomonas cichorii Stin Gerbera jamesonii StinEllada Chronika Benaki Phytopathological Institute15 85-88

Allen WR Matteoni JA 1991 Petunia as an indicator plant for useby growers to monitor for thrips carrying the tomatospotted wilt virus in greenhouses Plant Dis 7578-82

Al-Saady NA and Khan AJ 2006 Phytoplasmas that can infectdiverse plant species worldwide Physiol Mol Biol Plant 12263-281

Anonymous 2004 IRPCM lsquoCandidatus Phytoplasmarsquo a taxon forthe wall-less non-helical prokaryotes that colonize plantphloem and insects International J of Systematic andEvolutionary Microbiology 54 1243-1255

Anonymous 2015 Floriculture crops 2014 summary USDANASS ISSN 1949-0917 p 59 (httpusdamannlibcornelleduusdacurrentFlorCropFlorCrop-06-04-2015pdf)

Bertaccini A 2007 Phytoplasmas diversity taxonomy andepidemiology Frontiers in Bioscience 12 673-689

Broek VD Haydu JJ Hodges AW and Neves EM 2004 The Use ofIn-vitro Technique in Gerbera Breeding Revista Ceres 41386-395

Chaturvedi Y Rao AK Tiwari AK Duduk Band and Bertaccini A2010 Review Article Phytoplasma on OrnamentalsDetection Diversity and Management ActaPhytopathologica et Entomologica Hungarica 45 (1) pp31-69

Choudhary ML and Prasad KV 2000 Protected cultivation ofornamental crops - An insight Indian Horticulture 45(1) 49-53

Dijkstra J Khan JA Description of positive-sense singlestrandedRNA viruses Handbook of Plant Virology Khan JADijkstra J (eds) ndash New York USA 2006 p 253-388

Edwardson JR Christie RG 1987 Cucumoviruses Virusesinfecting forage legumes Gainesville No 1 p 143-1214

Elizabeth I Brisco-McCann and Hausbeck MK 2016 Diseases ofGerbera in book RJ McGovern WH Elmer (eds)Handbook of Floristsrsquo Crops Diseases Handbook of PlantDisease Management DOI 101007978-3-319-32374-9_18-1

Elliott DR Lebas BSM Ochoa-Corona M Tang J Alexander BJR2009 Investigation of Impatiens necrotic spot virusoutbreaks in New Zealand Australasian Plant Pathology38490-495

Farhood S and Hadian S 2012 First report of Alternaria leaf spoton Gerbera (Gerbera Jamesonii L) in North of Iran Advancesin Environmental Biology 6(2) 621-624

Fauquet CM Mayo MA Maniloff J Desselberger U and Ball LA2005 Virus Taxonomy Eighth Report of the InternationalCommittee on Taxonomy of Viruses ElsevierAcademic PressLondon

Finlay JR 1975 Cucumber mosaic virus in gerbera AustralianPlant Pathology Society Newsletter 4 (2) 14

Francki RIB Mossop DW Hatta T 1979 Cucumber mosaic virus CMIAAB Descriptions of plant viruses No 213 (No 1revised) p 1-6

Gautam KK Srivastava A Kumar S Snehi SK Raj SK andNautiyal CS 2015a First report of lsquoCandidatus Phytoplasmaasterisrsquo (16Srl group) associated with yellows disease ofgerbera (Gerbera jamesonii) from India New Disease Reports31 24

Gautam KK 2015b Ph D Thesis ldquoMolecular detection andcharacterization of a strain of Cucumber mosaic virusinfecting Petunia and Gerbera and their diseasemanagementrdquo Lucknow University Lucknow

Gautam KK Raj R Kumar S Raj SK Roy RK Katiyar R 2014Complete sequence of RNA3 of Cucumber mosaic virusisolates infecting Gerbera jamesonii suggested its groupingunder IB subgroup VirusDisease 25 398-40

Gautam KK Kaur C Raj R Kumar S Raj SK Purshottam DK andRoy RK 2017 Elimination of Cucumber mosaic virus fromgerbera (Gerbera jamesonii) cv Zingaro through in vitrochemotherapy of capitulum explants Indian Journal ofBiotechnology 16 641-647

Gundersen DE and Lee I-M 1996 Ultrasensitive detection ofphytoplasmas by nested-PCR assays using twouniversalprimer pairs Phytopathologia Mediterranea 35 144-151

Hakkaart FA 1968 A virus disease of Gerbera jamesonii new hostfor tobacco rattle virus Neth Journal of Plant Pathology 74 28-9

Harrison NA and Helmick EE 2008 First report of a lsquoCandidatusPhytoplasma asterisrsquo-related strain associated with little leafdisease of Helianthus debilis in Florida USA Plant Pathology57 772

Hull R and Davies JW 1992 Approaches to non-conventionalcontrol of plant virus diseases Critical Reviews in PlantSciences 11 17-33

Kaper JM Waterworth HE 1981 Cucumoviruses Handbookof plants virus infections and comparative diagnosis Kurstak E (ed) Amsterdam Netherlands 1981 p 257-332

Korbin M 2006 Assessment of gerbera plants geneticallymodified with TSWV nucleocapsid gene Journal of Fruit



and Ornamental Plant Research Vol 14 (Suppl 1)Korbin M Podwyszyntildeska M Komorowska B Wawrzyntildeczak

D 2002Transformation of gerbera plants with tomatospotted wilt virus (TSWV) nucleoprotein gene Acta Hort572 149-157

Kumar S 2009 PhD Thesis Molecular characterization ofCucumoviruses causing severe mosaic and ringspotdiseases in chrysanthemum and development of theirmanagement strategies University of Lucknow Lucknow

Lamberti F Tacconi R Marinari A Derrico FP and Basile M1987 ldquoMajor plant parasitic nematodes associated withflower crops in Italy and their controlrdquo Difesa delta Pinate10 77-84

Lee I-M Gundersen-Rindal DE Davis RE and Bartoszyk M 1998Revised classification scheme of phytoplasmas based onRFLP analyses of 16S rRNA and ribosomal protein genesequences International J of Systematic Bacteriology 48 1153-1169

Lee I-M Hammond RW Davis RE and Gundersen DE 1993Universal amplification and analysis of pathogen 16SrDNA for classification and identification of mycoplasmas-like organisms Phytopathology 83 834-842

Li Y Li F Liu YL Li L Chen JL Tang XY Chen HR 2008Identification of the pathogens causing root rot of Gerberajamesonii in Yunnan J South China Agric Univ 34

Manju P and Subramanian S 2015 Survey Of Plant ParasiticNematodes Associated With Gerbera In Tamil NaduIJSN Vol6 (4) 586-589

Marques E Borges C Uesugi CH 2016 Identification andpathogenicity of Pseudomonas cichorii associated with abacterial blight of gerbera in the Federal District FederalHortic Bras vol34 no2

Martin FN Blair JE Coffey MD 2014 A combined mitochondrialand nuclear multilocus phylogeny of the genusPhytophthora Fungal Genet Biol 6619-32

Marys E Mejiacuteas A Rodriacuteguez-Romaacuten E Avilaacuten D Hurtado TFernaacutendez A Zambrano KGarrido M Brito M 2014 Thefirst report of tomato spotted wilt virus on GerberaandChrysanthemum in Venezuela Plant Disease 98(8)1161-1161

Miller JW Knauss JF 1973 Bacterial blight of Gerbera jamesoniiincited by Pseudomonas cichorii Plant Disease Reporter Vol57No6 pp504-505

Mirkova E and Konstantantinova P 2003 First Report ofAlternaria Leaf Spot on Gerbera (Gerbera jamesonii HBoluxex J D Hook) in Bulgaria Journal of Phytopathology151 323-328

Nagesh M and Paravatha Reddy P 2000 ldquoCrop loss estimation incarnation and gerbera due to root-knot nematodeMeloidogyne incognita (Kofoid and White) Chitwoodrdquo PestManagement in Horticultural Ecosystems 6 158-159

Nagesh M and Parvatha Reddy PN 2001 ldquoPathogenicity ofselected antagonistic soil fungi egg masses under in vitro

and in vivo conditionsrdquo Journal of Biological Control 15 63-68Ninkovic V Feng Y Olsson U and Pettersson J 2013 Ladybird

footprints induce aphid avoidance behavior BiologicalControl 65 63-71

Raj SK Khan MS Kumar S Pratap D and Vishnoi R 2008Cucumber mosaic virus Infecting Vegetable and Pulse Cropsin India Characterization Diagnosis amp Management of PlantViruses Vol 3 Vegetable and Pulse Crops 39-62 (Eds GPRao P Lava Kumar and Ramon J Holguin Pena) Studiumpress LLC Texas USA

Ravnikar M Vozelj N Mavriegrave I Gvigelj SD Zupanegraveiegrave M andPetroviegrave N 2003 Detection of Chrysanthemum stem necrosisvirus and Tomato spotted wilt virus in chrysanthemumAbstracts 8th International Congress of Plant PathologyChristchurch New Zealand ICPP

Reddy PP 2016 Gerbera In Sustainable crop protection underprotected cultivation Springer Singapore pp 355-362

Schmelzer K 1966 Das Tabakmauche-Virus (Tobacco rattle virus)on Gerbera jamesonii Bolus Arch Gartenb 14 89-92

Schneide B Seemuumlller E Smart CD and Kirkpatrick BC 1995Phylogenetic classification of plantpathogenicmycoplasma-like organisms or phytoplasmas In RazinS and Tully J G (eds) Molecularand Diagnostic Proceduresin Mycoplasmology Vol I Molecular CharacterizationAcademic Press IncSan Diego California USA pp 369-380

Shalini B Hanumantharaya L and Chandrashekar SY 2019Management of gerbera whitefly (Bemisia tabaci Genn)under protected condition Journal of Entomology and ZoologyStudies 7(4) 713-717

Siddique ABM 2005 Phytoplasma association with gerberaphyllody in Australia Journal of Phytopathology 153 730-732

Spanograve R Marzachigrave C Mascia T Bubici1 G and Gallitelli D 2011aCandidatus phytoplasma asterisrsquo from Gerbera jamesonii inapulia southern Italy Journal of Plant Pathology 93(4) 63-89

Spanograve R Mascia T De Lucia B Torchetti EM Rubino L andGalliteli D 2011b First Report Of A Resistance- BreakingStrain Of Tomato Spotted Wilt Virus From Gerbera jamesoniiApulia Southern Italy Journal Of Plant Pathology 93 (4) 63-89

Stankoviaelig I Bulajiaelig A Vuegraveuroviaelig A Ristiaelig D Joviaelig J andKrstiaelig B 2011 First Report of Tomato spotted wilt virus onGerbera hybrida in Serbia Plant Disease 95(2) 226

Stouffer RF 1965 Isolation of Tobacco rattle virus from Transvaaldaisy Gerbera jamesonii Phytopathology 55 501

Sudhagar S 2013 Production and Marketing of Cut flower (Roseand Gerbera) in Hosur Taluk International Journal of Businessand Management Invention 2(5) 15-25

Suzuki M Kageyama K Ichikawa T and Uchiyama T 2009Occurrence of Pythium root rot of gerbera caused by Pythiumhelicoides (Abstract in Japanese) J Phytopathology 75237



Tanno K Maejima K Miyazaki A Koinuma H IwabuchiN Kitazawa Y Nijo T Hashimoto M Yamaji Y Namba S2018 Comprehensive screening of antimicrobials to controlphytoplasma diseases using an in vitro plant-phytoplasmaco-culture system Microbiology164(8)1048-1058

Troisi M Bertetti D Garibaldi A and Gullino ML 2010 Firstreport of powdery mildew caused by Golovinomycescichoracearum on gerbera (Gerbera jamesonii) in Italy PlantDisease 94 (1) 130-130

Varma A Jain RK Bhat AI 2002 Virus Resistance TransgenicPlant For Environmentally Safe Management of VirusDiseases Indian J of Biotechnology V (1) 73-76

Vazquez GL Aquino MJ Norman MT Martinez FA SandovalRV and Corona RMC 1997 First report of white rust ofgerbera caused by Albugo tragopogonis in North AmericaPlant Disease 81(2) 228

Verma N Singh AK Singh L Kulshreshtha S Raikhy G HallanV Ram R and Zaidi AA 2004 Occurrence of Cucumber mosaicvirus in Gerbera jamesonii in India Plant Dis 88(10)1161-1161

Whipker BE 2014 Gerbera mottling and necrotic spotting E-Gro Alert Vol 3 No 4

Wolcan SM 2010 First report of downy mildew caused by Bremialuctucae on Gerbera jamensonii in Argentia Australasian PlantDisease Notes 5 98-100

Zhang LL 2009 Masterrsquos thesis Study on main viruses of Gerberajamesonii bolus with virus-free by tissue culture and its rapiddetection Northwest University of Science and TechnologyChina (httpwwwdissertationtopicnetdown 274429)

Zhang Z 2006 Flora fungorum sinicorum Botrytis Ramulariavol 26 Science Press Beijing p 277



France and California The Netherlands produces 420million stems of gerbera per year which is valued at 145million Netherlands guilders (Sudhagar 2013) Theproduction of gerbera was approximately US$ 220 millionin 2001 representing 70 million stems sold in US alone (Broeket al 2004) About 7 species were recorded in Indiadistributed in the temperate Himalayas from Kashmir toNepal at altitudes of 1300 to 3200 meters Gerberaproduction is maximum (2016 MT in 70 ha area) among theothers cultivated flowers such as carnation gladiolusmarigold rose tuberose in Uttrakhand Gerbera contributeswith a production of 17840 MT and stands fourth importantcut flower in India The total area of gerbera in India is 820ha with a cut flower production of 17 840 MT and looseflower of 3960 MT However maximum production ofgerbera comes from Uttarakhand (7 200 MT) whilemaximum area coverage is from Assam (600 ha) The shareof gerbera cut flower production in Karnataka is 200 MTand loose flower production is 580 MT (Anonymous 2015)According to DBT and Small Farmerrsquos AgribusinessConsortium India gerbera ranks as 2nd most domestic tissueculture flower crops in India after carnation anthuriumorchids in floriculture industry The cut flower sticks ofgerbera are been sold in market with the variable ratedepends on the flower quality and size According to recentsurvey of floriculture today gerbera farmers have recordedearnings of Rs 25000 - 30000- from an area of 134 sqmThe average income per unit area perhaps is the highest infloriculture ranging from Rs 100 to Rs 200 per sqmAccording to National Horticulture Board (NHB) of India2015-16 major gerbera producing states are Assam (1242Tones) Uttarakhand (514 Tones) Telangana (314 Tones)Karnataka (237 Tones) Meghalaya (092 Tones)Maharashtra (066 Tones) Tamil Nadu (052 Tones)Himachal Pradesh (030 Tones) Nagaland (004 Tones) andMizoram (003 Tones) Gerbera is grown commercially inIndia for export and domestic market In India we producevery high quality cut flower of the crop and millions of tissuecultured plants are produced Tropical Floritech Pvt Ltd inBangalore is the leading player in commercial cultivation inIndia (Chaudhary and Prasad 2000) The area under gerberacultivation in Karnataka is estimated at 25 ha withproduction of 53 lakhs cut flowers at an estimated value ofRs 15 lakh

PATHOGENS AND DISEASES AFFECTING GERBERACULTIVATION

Gerbera production is challenged by numerousdiseases caused by insect fungal bacterial nematodes viraland phytoplasma pathogens that affect its flower qualityand quantity The major pests (whitefly aphid leaf miner

thrips mites) diseases (powdery mildew collar rot root rotstem rot leaf spot) nematodes (root-knot spiral) and theirsymptoms biology spread and management have beendiscussed by Reddy 2016 The details of diseases caused byinsect fungal bacterial nematodes viral and phytoplasmapathogens are described as under

Insect-Pest DiseasesInsect-Pest incidence is the major factor responsible for

yield reduction in gerberas Gerberas have a wide variety ofpests such as aphids (Myzus persicae and Aphis jabae) (whichtransmit Cucumber mosaic virus and Potyviruses in nature)Leaf miner (Liriomyza trifolii and L soncho) Mites(Steneotarsonemus pallidus and Polyphagotarsonemus latus)Western flower thrips and caterpillars The whiteflies(Bemisia tabaci Genn Hemiptera Aleyrodidae) are majorpotential insect pests of greenhouse gerberas (Table 1)(Shalini et al 2019) These insect pests affect plant health bysucking of their sap as well as by transmitting many diseasesfrom infected to healthy plants

Nematode ProblemsAlthough a multitude of plant parasitic nematodes are

found associated with gerbera elsewhere in the world(Lamberti et al 1987) root knot nematodes belonging toMeloidogyne spp are predominant in India (Nagesh andParvath Reddy 2001) In India yield loss in gerbera due toMeloidogyne incognita was reported to be 311 (Nagesh andParvatha Reddy 2000) A survey was conducted in thedifferent districts of Tamil Nadu in the year of 2013 in orderto determine the most important plant parasitic nematodesspecies associated with gerbera The analysis of soil androot samples collected from the rhizosphere of gerbera ineach district revealed the presence of only five species ofplant parasitic nematodes These are Meloidogyne incognitaHelicotylenchus multicinctus Pratylenchus coffeaeTylenchorhynchus spp and Rotylenchulus reniformis Thepresent investigation revealed that M incognita is one of theserious limiting factors in commercial cultivation of gerberaunder polyhouse conditions present in Tamil Nadu (Manjuand Subramanian 2015) Nematodes also transmit somediseases caused by viruses such as Tomato bushy stunt virusand other Nepoviruses which also affect gerbera and otherplants grown in polyhouseglasshouse conditions

Fungal DiseasesGerberas have several fungal disease problems such

as root rots (by Pythium irregulare Rhizoctonia solani) crownand root rot (by Phytophthora cryptogea P drechsleri)Sclerotium rot (by Sclerotium rolfsii) Botrytis blight (by Botrytiscinerea) powdery mildews (by Erysiphe cichoracearum Oidium





















Zhang 2006



Li et al 2008



Martin et al 2014







Suzuki et al 2009



Reddy 2016



Reddy 2016








































Leafhoppers































































































































































































Zhang 2006



Li et al 2008



Martin et al 2014







Suzuki et al 2009



Reddy 2016



Reddy 2016








































Leafhoppers


















































































































































































































Leafhoppers

































































































































































































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Documents

Diseases affecting gerbera cultivation and their control