Climate Factors affecting seed production

8/18/2019 Climate Factors affecting seed production

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Factors afecting

Vegetable SeedProduction

Dr. P. Syam Sundar Reddy

Assistant Proessor (Hort.)


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• The seed production of varieties andhybrids of vegetables should be carriedout carefully in the region where theseare well adopted.

• The climatic factors have direct bearing

on the quality seed production.• These includes, light (duration, intensity

and photoperiod), temperature (low,

moderate, high and very high), rainfall /snowfall (total as well as distribution)and wind (direction and velocity).


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• Te !arious actors afecting

"uality seed #roduction includes,• 1.Edaphic factors

• . !limatic factors

• ". #roduction factors

• $. #ost harvesting handling of seed

• %. &eed quality control factors


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$. %da#ic actors

• &oil for seed production should have optimummoisture, good te'ture and structure.

• ierent vegetables have dierent soil

requirements and in general, loams are thebest.

• !lay soils in high rainfall area become sic*and cause lac* of aeration which aects seed

quality. &oil p+ should be around , as neutral.• The problematic soil li*e saline soil and acidic

soil are to be avoided for seed production.

• p+ aects seed production in sensitive plants

li*e legumes and vegetables .


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• -ertile soils are highly preferable for seedproduction.

•

&oil should have adequate macro and micronutrients and microbial load for producingvigorous and viable seeds.

• -or e'ample oron deciency causes blac*

rot in cole crops particularly cabbage andcauli0ower and hollow heart in garden pea.

• olybdenum causes physiological disorderli*e whiptail in crucifers.

• E'cess nitrogen results more of vegetativegrowth that leads to more proneness todiseases and insects resulting reduction in

seed quality and yield.


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• 2, # and 3 in balanced dose increases

seed yield and improves seed qualityand induce resistance.

• The seed production should be avoidedunder soil moisture stress or poor

drainage conditions.

• 4ll drained soils causes chlorosis and wiltdiseases.

• The soils should be free from soil bornepathogen and nematodes especially forseed production in horticultural crops.


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• -or producing good quality, soil shouldfree from pathogens.

• -or e'ample bacterial wilt inoculumavailable in most soils infests solanaceousvegetables tomato, brin5al and chilli.

• -usarium wilt in many vegetables spreadsfrom seed to soil.

• 6ilt gets established through plantingmaterial (seeds) and thus spreads furtherfrom the soil.

• &oil should also be free from weed seeds.


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&. 'limatic actors

• efore seeds can be produced fromvegetables it is necessary for the crop to0ower.

• -lowering is required by the plant forse'ual reproduction and maintenance ofgeneration.

•

&ome plant species pass from vegetativephase to the reproductive phase withspecial requirement or stimulus, whereasin others such stimulus is not required.


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• &pecies which have a special

physiological requirement to pass fromthe vegetative phase to reproductivephase are generally either dependenton day length (photoperiod) or have a

low temperature requirement(vernali7ation).

• 2ot only photoperiod and temperature

but some other climatic factors, e.g.rainfall, wind etc. are also responsiblefor best yield of high quality seeds.


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• The ma5or environmental factors

in0uencing vegetable seedproduction are 8

• Poto#eriod

•Tem#erature

• Rainall

• Humidity

• ind• 'old

• nsect acti!ity


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A. Poto#eriod

• #hotoperiod in0uences vegetable seedproduction by aecting photosynthesis andday length.

• 6ithin the limits of each crop plant, thehigher the light intensity, the higher will bethe rate of photosynthesis required tomanufacture the important constituents of

the seed.

• ierent crop plants have dierentrequirements of photoperiodism.


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• Transition rom !egetati!e to tere#roducti!e #ase in some vegetable

crop plants can occur only at the seasonwhen the days are of particular length,and if the plants are *ept in the wrongday length, they remain in vegetativephase for longer time.

• #lants can be classied into three maingroups according to the specic duration

of light and dar* requirement in each $hour period or cycle in order to initiate0ower, vi7. sort*day #lants+ long*day#lants and day*neutral #lants.


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• Short-day Plants : This group includes specieswhich will not 0ower unless the day light period isshorter than a particular critical time, which is

between 19 and 1 hours,• E'. :maranthus sps, soybean, pepper (some

varieties), *idney bean.

• Long-day Plants : These include plants which will

0ower only when the light period is greater than acritical time.

• The critical photoperiod for most long;day plants isbetween 1 and 1$ hours,

•

E'. spinach, radish, cabbage, cauli0ower, broccoli,turnip etc.

• Day-neutral Plants : This group does not have aspecic day length requirement for 0owering, fore'ample, tomato, brin5al, lettuce, cucurbits, carrotetc.


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,. Tem#erature

•

Temperature plays a ma5or role in seedproduction.

• &eed germination, seed crop growth and maturityof vegetable seeds are in0uenced by

temperature.• Too high temperature during seed crop maturity

brings forced maturity and poor seed quality.

•


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• +igher temperatures and strong winds causedesiccation of pollen grains and drying of

stigma results in poor seed set and seedquality.

• +igh temperature adversely aects seedproduction due to drying of anthers in lab;lab> 0ower shedding in tomato and chilliesand production of higher percentage of hardseed in leguminous vegetables.

•


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• epending upon the vernali7ation requirement,vegetable crops are grouped in to8

•

Annual : ?egetable species which do not havevernali7ation requirements for 0ower initiation,such crops produce 0ower and seed in the rstyear, e.g. tropical radish,

•

Biennial : iennial plants tend to remain invegetative stage in the rst year of growth andthey 0ower and produce seed in the second year,e.g. beet, carrot, cabbage and biennial radish etc.ost of the biennial plants require vernali7ation for

0ower initiation.

• Perennial : #erennial plants survive for severalyears producing 0owers and seeds each year. ostvegetables are, however, annuals and biennials.


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• 4n some vegetables, high temperature inhibitsdevelopment of ovules and fruits and causesshedding of 0ower buds and young pods / fruits.

• +igher temperature results in shriveling ofseeds lower yield and poor seed quality.

• Temperature between 24 - !"# is mostfavourable for activities of pollinators particularly

bees.• #ollinators are an important component in

vegetable seed production and without thesequality seed production is not possible particularly

in cross and often cross;pollinated vegetables.• These pollinators stop wor*ing at low (belo$ 2%"

#) or high temperature (beyond !" #), heavyrains, strong winds which hampers quality seed

production


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'. Humidity• +igher @+ AB9 per cent cause heavy fower

drop and during maturation will lead toproduction of blonded seeds (eg peas,) ,@+C$9 per cent leads to production of hard seeds.

• -lowering, pollination and seed setting intemperate vegetable needs low humidity anddry weather and moderate to low humidity insub;temperate and tropical vegetable

varieties.• +igh humidity and low temperature also

encourages production o diseased seeds.

• &lightly warm dry climate is suitable for

production of disease free seed.


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D. Rainall• E'cessive rain, apart from aecting pollination,

leads to a higher incidence o diseasesresulting in mould attac* and seeddiscoloration.

• 4t may also results in delayed maturity and at

the time of maturation leads to pre;germination or sprouting of seeds in standingcrops (eg. peas, beans).

• &trong wind and heavy rainfall at or near

harvest may cause heavy seed losses throughshattering and also complicate the harvestingoperations (e.g. amaranthus).

• @ain at physiological maturity aects the initial

quality and storability


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%. ind• 6ind is necessary or pollination in wind

pollinated crops. 4mproves seed setting in highlycross pollinated crops li*e onion and crucifers.

• :t times winds act as a source o contaminationand protection of seed crops has to be done

using barriers.• +eavy winds may carry pollen too far or prevent

deposition on stigma thus reducing seed set.

• ry winds also desiccate pollen resulting in loss

of viability and development of hard seeds inlegumes.

• +eavy winds results in lodging and shattering ofseeds / pods.


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F. 'old

• Temperatures below 19=! may not besuitable for tropical crops.

• 4t will aect anthesis, pollengermination, pollen fertility delayedgrowth and maturity, incompletee'ertion, reduced lling, cho*ing of

panicle and incidence of pest anddisease.


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-. nsect acti!ity

• 4nsects are benecial as well as harmful inseed production.

• 4n onion rearing D honeybees hives / haincreases the seed production by "9 per cent.

•

&imilarly the insects acts a source ofcontamination and in insect pollinated cropsone *ilometer distance is required as isolation.

• 4nsects damage seeds right from the pod stage

till harvest and account for 9;"9 of the seedproduction losses e.g. in cucurbit red pump*inbeetle and beetles in pulses are pollen eaters.


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. Production actors

•

$. Selection o suitable #roductionen!ironment based on ado#tability• -ree from volunteer plants, weed plants and

other crop plants.

•

4n the proceeding season the same crop shouldhave not been grown.

• :void areas where isolation is a problem.

• +aving a well distributed rainfall in the cropping

period.• :void areas of very high and low rainfall.

• #revalence of cool and dry weather is preferable.

• :void high temperature and relative humidity

areas where germination is poor.


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• :void heavy windy areas.

•

:void coastal belts and marshy places andheavy windy areas.

• :void areas of endemic diseases and pests.

• &elect compact areas for hybrid seed

production.

• :vailable of s*illed labourers especially inhybrid seed production of crops.

•

2ear the processing operations withtransporting facilities and mar*eting

• facilities.


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• &. Selection o land

• &elect well leveled eld for uniformmaturity.

• &elect nearest to irrigation sources.

• &elect fertile elds.

• :void weedy elds particularly thepresence of abno'ious weeds.

•

:void problem elds li*e al*aline,saline and sodic soils.

• :void sic* elds.


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• . Selection o season

• #roper season for specic *ind of crop.

•


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• /. Selection o Seeds

•

The seed used for raising a seed cropshould be of *nown purity,appropriate class (farmers can

produce certied seed).• reeder &eed can be produced only

by the university and -oundation&eed by &tate &eed -arm / andinvariably obtained from an

authori7ed oFcial agency.


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• 0. Pre#aration o land1

• The land for the seed crop must beprepared well.

• Good land preparation helps inimproved germination, deepploughing results in destruction ofpotential weeds.

• 4t also aids in water managementand good uniform irrigation.

• #erfect leveling is very important.


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• 2. Pre*so3ing treatment

• &eeds should be appropriately treated.

• #re;sowing seed treatments with nutrients. &hefollo$ing points should be considered .

• uration of soa*ing

• &oa*ing water to seed ratio.

•


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• 4. Seed rate and nursery

• &eed rate should be based on seed lot viabilityand vigour.

• 4f not there will be lot of gaps in the eld.

• 4ndirect sown crop or seedlings may not be

suFcient to cover the targeted area totransplant or if high the seed will be wasted.

• Iine sowing is advisable for seed crop adoptingcorrect spacing then only we can achieve

required population producing equal opportunityto each plant to develop and mature which isnot possible in broadcasted crop


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• $. Time o #lanting

• &. 5etod o #lanting 6 so3ing

• . De#t o so3ing

• /. eeding

• 0. rrigation

• 2. 7utritional actors

• 4. Roguing• 8. Diseases and #est control

• 9. Har!est


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/. Post ar!est andling o seedcro#

• $. Har!esting and tresing

• &. Drying and grading

•

. Seed treatment• /. Pac:aging+ labelling and

sealing

•

0. 5o!ement and storage


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0. Seed "uality control actors

• $. Seed moisture

• &. -ermination #er cent

•

. Vigour• /. Storage lie

• 0. Seed ealt

•

2. 5ecanism o control

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Climate Factors affecting seed production