Tree improvement programmes for forest health.docx

8/9/2019 Tree improvement programmes for forest health.docx

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Tree improvement programmes for forest

health – can they keep pace with climate

changes? A. Yanchuk and G. Allard

Alvin Yanchuk is with the Research Branch of the British Columbia Forest Service, Victoria,British Columbia, Canada.

Gillian Allard is Forest Protection Officer in the Forest Management ivision, Forestr!

e"artment, F#O, Rome.

Can tree im"rovement "rogrammes develo" $generic% resistance to offset "otential new "est and

disease "roblems that ma! arise more ra"idl! with climate change&

#s forest geneticists consider "h!siological ada"tations of forest tree "o"ulations under various

climate change scenarios, the! must also ta'e into account li'el! im"acts from new insect "estand disease introductions, as well as increased natural disturbances from native "ests. (hat

lessons can be learned from "ast investments in disease and "est resistance research and genetic

im"rovement, "articularl! with the challenges of climate change scenarios& Can more generic

and general resistance be develo"ed to offset "otential new "est and disease "roblems that willarise within a time frame of less than a decade&

)he world*s main commercial tree im"rovement "rogrammes have focused "rimaril! on

"roductivit! im"rovements in the first few generations of breeding, but the! have sometimesincluded an insect "est and disease resistance com"onent. Man! "est and disease resistantindividuals, and even s"ecific resistance genes, have been found in forest tree s"ecies, and some

are currentl! em"lo!ed in breeding.

)his article summari+es the results of a recent worldwide surve! of research on insect anddisease resistance which suggests that although some targeted resistance "rogrammes have had

substantial im"acts on im"roving the health of "lanted forests, most of the gains have been for

onl! a small number of maor commercial s"ecies and have ta'en decades to develo". )he article

suggests that "ast a""roaches ma! not serve well under ra"id climate change, and also identifiesfive future challenges that could undercut the "otential for tree im"rovement "rogrammes to

im"rove forest health in changing climates.

INF!"N#" $F #I%AT" #&ANG" $N '"(T AN)

)I("A(" '*$+"%(

Climate change is e-"ected to result in or reuire large/scale movement of s"ecies, and

"o"ulations within s"ecies, into climatic +ones where the! ma! not currentl! e-ist. Bold new


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forest management strategies will be needed to offset ada"tational lags of s"ecies and their

"o"ulations to maintain "roductivit! and forest health. )ree vigour and "roductivit! will be the

first line of defence against insect "ests and diseases.

Furthermore, ranges of insect "ests are e-"ected to e-"and under several climate change

modelling scenarios 0e.g. nun moth, Lymantria monacha1 g!"s! moth, Lymantria dispar 20Vanhanen et al ., 34452. iseases and insect "ests continue to be introduced and to invade or

threaten regions outside their natural distribution ranges 06ovett et al ., 34472. (arming climate isthought to be a maor cause of e"idemic outbrea's of native diseases and "ests that are causing

relativel! new and catastro"hic "roblems1 recent e-am"les include othistroma needle cast

disease 0(oods, Coates and 8amann, 34492 and mountain "ine beetle 0#u'ema et al.,344:2 inwestern Canada.

#s warming climate is thought to

trigger outbrea's of othistromaneedle cast disease 0shown in

lodge"ole "ine, Pinus contorta2,resistance mechanisms that ma!

reduce infection to severals"ecies of needle cast fungi

would be worth "ursuing

#. ;anchu'

*"(!T( $F *"(I(TAN#" +*"")ING '*$G*A%%"(

T$ )AT"


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# surve! of the literature to evaluate the effectiveness of tree breeding research for disease and

"est resistance, carried out b! F#O with assistance from the British Columbia Forest Service,

Canada, classified activities according to four levels of breeding "rogramme develo"ment<

• Status = > large breeding "rogrammes that have resulted in o"erational "lanting of

resistant material 0seed/orchard seed or other "ro"agule t!"es21

• Status 3 > large research or breeding "rogrammes that have not !et resulted in o"erational

"lanting1

• Status ? > large research or breeding

"rogrammes that have identified genetic variation in resistance in genetic@"rovenancetrials1

• Status A > studies that have identified genetic variation in resistance in small research

seedling or clonal trials.

#lthough the technical a""roaches that can be a""lied are somewhat "redetermined b!these levels, three technologies were also identified to categori+e the initiatives further<

• traditional "lant breeding methods1

• molecular biolog! a""roaches1

• genetic engineering.

# total of 374 activities on breeding for "est and disease resistance in forest trees were recorded

in the review 0F#O, 344:2. )he list was not intended to ca"ture all "ublications on resistance in a "articular s"ecies, as some resistance "rogrammes 0e.g. that for fusiform resistance in Pinustaeda2 have been re"orted in hundreds of scientific "a"ers. )he intention was rather to re"resent

a sam"le of the literature in each "rogramme area. )he )able summari+es some of the

"rogrammes that have had the largest im"act to date.

# relativel! successful diseaseresistance "rogramme targets

white "ine blister rust

0Cronartium ribicola2 in orth#merica1 a com"le- bar'

reaction 'ills tissue around theinfection in a Pinus strobus tree

with tolerance to the disease

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#. ;anchu'

(urvey summary

By forest tree species. )hirt!/si- tree genera were re"resented. Pines 0 Pinus s"".2 and "o"lars

0 Populus s"".2 were the two most commonl! investigated genera, together re"resenting more

than half of the activities recorded 0Figure =2.)he most studied tree s"ecies included Pinus radiata 0=7 records2, P. taeda 0nine records2, and P.

monticola and P. ponderosa var. ponderosa 0si- records each2. Other s"ecies with at least four

activities were Picea abies, Pinus contorta, Betula pendula, Cryptomeria japonica, Eucalyptus globulus, evea brasiliensis, Pinus lambertiana and Populus deltoides.

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By pest type and species. #bout 9A "ercent of re"orted activities investigated tree resistance to

disease s"ecies, ?7 "ercent targeted forest insect "ests and 7 "ercent investigated both "est t!"es.Resistance to mammals was the focus of onl! si- activities 0about 3 "ercent2, and one activit!

dealt with nematode resistance.

)he most commonl! targeted insect "est s"ecies included Chrysomela scripta 0five activities2

and Pissodes strobi and !hecodiplosis japonensis 0four activities each2. )he most commonl!targeted disease s"ecies included Cronartium ribicola 0=: activities2 and Cronartium "uercuum

0seven activities2. Four activities each addressed #iplodia pinea, eterobasidion annosum,

$elampsora larici%populina and &phiostoma ulmi.

By country. )he maorit! of research activities are "ublished in develo"ed countries, led b! the

nited States with almost ?D "ercent of all activities 0Figure 32, although some emergingdevelo"ing countries such as China 0about : "ercent2, Endia 0? "ercent2 and Bra+il 0= "ercent2 are

active or have at least "ublished and disseminated some results.

By approach. #bout 7: "ercent of the research focused on traditional "lant breeding methods.

enetic engineering was the focus of almost =9 "ercent of the activities and molecular biolog!

almost =? "ercent. #bout 9 "ercent used a combination of the three a""roaches.

By status of breeding programme. #bout 7? "ercent of all research activities are Status A, 33

"ercent are Status ? and onl! 7 "ercent are Status 3. Gust D "ercent of the recorded activities are

Status =, i.e. at the stage of "lanting resistant material o"erationall!1 furthermore man! of theseactivities, although carried out b! different organi+ations, re"resent wor' with the same tree

s"ecies and "est or disease "roblem.

=Ensect "est and disease resistance breeding "rogrammes, b! tree

genus

3

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Ensect "est and disease resistance

breeding "rogrammes, b!countr!

Impact of resistance work in planted forests

En general, the surve! clearl! shows that des"ite a large bod! of "ublished research over more

than 94 !ears, from hundreds of research initiatives or "rogrammes around the world, relativel!few "rogrammes have develo"ed resistant material for o"erational "lanting. Practical im"acts

from resistance breeding "rogrammes have onl! been documented for four to five maor

commercial "est and disease "roblems.

For disease resistance, the two most successful "rogrammes a""ear to be the fusiform rust

resistance im"rovement in Pinus taeda and Pinus elliottii in the southern nited States, and thewhite "ine blister rust resistance "rogrammes in the Enland Hm"ire region of southern California

and the Pacific orthwest of orth #merica. Pinus lambertiana resistance to blister rust inCalifornia and southern Oregon, nited States, is also notable. )he most im"ressive

documentation of success has been for fusiform resistance1 average worth of "lantations

established with fusiform/resistant P. taeda im"roved 7 to A4 "ercent over "lantations establishedwith susce"tible stoc', while im"rovements for P. elliottii ranged from A4 to D4 "ercent 0Brawner

et al.,=DDD2.

ains from the first/generation "rogrammes of non/maor gene resistant stoc' in Pinus strobus

range from ? to 54 "ercent survival 0with one rare e-am"le of maor gene resistance in Pinus

lambertiana and P. monticola inferring =44 "ercent survival in the sim"lest situation IJinloch etal.,=DDDK2. )hese figures ma! be underestimates as the survival of more recentl! "lanted material

ma! be higher1 nevertheless, the results clearl! show that genetic gains are "ossible andim"ortant.

Several "rogrammes 0e.g. chestnut resistance to blight2 seem to be on the verge of having novel

materials read! for use1 however, a long time will be reuired before their ecological or

economic im"acts can be evaluated. othistroma/resistant breeds in Pinus radiata have been


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develo"ed, but the "roblem has largel! been addressed through silvicultural "ractices 0Mead,

34492.

En com"arison with disease resistance, "est resistance "rogrammes are less well develo"ed andhave resulted in less material that has reached large/scale reforestation "rogrammes, although

there is substantial wor' in the area 0as shown in the )able2. )he surve! revealed onl! two "rogrammes using traditional "lant breeding methods that could be classified as Status =, one for

s"ruce a"hid 0 Elatobium abietinum2 resistance 08arding,Rouland and (ellendorf, 344?2 inHuro"e and the other for s"ruce terminal weevil 0 Pissodes strobi2 resistance in British Columbia,

Canada 0Jing et al.,=DD52. (or' on transgenic material for resistance to stem/boring and leaf/

eating insects is increasing1 o"erational "lanting of this material is in its infanc! but has beenre"orted with "o"lars in China 0Hwald, 8u and ;ang,34472. (or' on Eucalyptus resistance to a

number of leaf insects is increasing, but to the authors* 'nowledge the resistance has not been

incor"orated in materials being "lanted commerciall!.

Considerable time and resources have been invested to obtain resistant genot!"es, gain

e-"erience in their use and achieve im"acts in im"roving "lantation health. Enitiating anim"rovement "rogramme for a tree s"ecies, even for a few sim"le traits, reuires substantiall!

more !ears than for a cro" s"ecies. (ith a long "rocess involving selection of germ"lasm forfield testing, rearing of test stoc', test establishment and measurements at a""ro"riate ages,

selection of best material and establishment in seed or hedge orchards, it is not sur"rising that the

successful "rogrammes have ta'en one, two or even more decades to identif! and develo"silviculturall! useful genetic resistance.

Esolation bags on western red cedar 0!huja plicata2

for controlled "ollination for deer browse resistance

studies

#. ;anchu'

S"ruce terminal weevil 0 Pissodes strobi2 larvae

migrate down the leader to girdle and 'ill the to" ofthe tree1 a breeding "rogramme for this "est in

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western Canada is one of the few insect resistance

"rogrammes that has reached the o"erational "lanting stage

#. ;anchu'

# few surviving lodge"ole "ine

trees resistant to mountain "ine

beetle in a !oung 0age 34 !ears2famil! trial1 high levels of attac'

in such long/term research field

installations are t!"icall! anim"ortant first $genetic

screening% for resistance to bar'/chewing insects

#. ;anchu'


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6odge"ole "ine "rovenance test

at age ?4 !ears1 field tests suchas these have been im"ortant for

stud!ing the effects of climate

change on ada"tive genetic

variation in growth "otential and "est and disease resistance

among forest tree "o"ulations

#. ;anchu'

#&A"NG"( F$* "FF"#TI," *"(!T( IN

#&ANGING #I%AT"(

)ifficulty of finding specific mechanisms that e-plain plant or tree resistance

(hile man! insect "est and disease resistance traits can be scored relativel! easil! b! observing

the "resence or absence of the "est or disease on an individual tree, detailed "henot!"ic

assessments of host reaction or "est behaviour 0e.g. landing on and then leaving a tree2 arereuired to develo" a better understanding of what general mechanisms of resistance are at wor'.

ecades of research on herbivor! in Betula pubescens 0e.g. 8au'ioa, 344?2 have uncovered a

wide range of variations in birch that can im"art resistance. For instance, there is a larges"ectrum of leaf com"ounds that change over the growing season1 the level of resistance varies

b! herbivore s"ecies1 and sim"le changes in nutrients, water content and leaf toughness were

found to be as im"ortant as an! of the more com"le- and detailed anatomical or chemical

"rofiles in birch genot!"es 0Rii"i et al.,34492. )o identif! mechanisms of resistance that ma!im"art some general resistances to classes of insect "ests and diseases, and to incor"orate this

'nowledge into "rogrammes that can "otentiall! deliver resistant germ"lasm, will be difficult but


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e-tremel! valuable. evelo"ment of general resistance becomes more critical if it is not "ossible

to "redict what future insect "est s"ecies or "athogens will be encountered with climate change.

Transfera.ility of research on wild trees to pedigreed trees in genetic

improvement programmes

Studies carried out on trees in natural settings will not necessaril! assist breeding "rogrammes in

develo"ing more resistant germ"lasm. Much research on insect "est or disease interaction with

host trees in the wild is im"ortant for modelling "ur"oses 0e.g. on s"read rates and im"acts inwild forests2 and is of evolutionar! interest, but it ma! not be "ossible to e-tra"olate the results

to s"ecies or "o"ulations that have been artificiall! migrated under climate change ada"tation

strategies 0Millar,Ste"henson and Ste"hens, 34452. (or' with "edigreed material from breeding

"rogrammes, if available and adeuatel! challenged b! various "ests or diseases, ma! also beable to "rovide the basic information needed for stand or landsca"e im"act models.

)ecreasing resources for traditional genetic improvement of forest trees

En s"ite of the im"ressive "rogress to date in some "rogrammes, it is li'el! that fewer resources

will be available in the future for the stud! of s"ecific host/"est interactions in classical tree

im"rovement "rogrammes. loball!, traditional training in uantitative genetics > a necessar!

s'ill set in tree breeding > has been waning 0Hisen, 344:1 Jnight, 344?1 Morris, Hdmeades andPehu,34472. En addition, man! of the largest and most successful tree breeding "rogrammes are

currentl! struggling because of maor financial and structural changes in the forest industr!

0B!ram, Miller and Rale!,34472. #vailable research resources will need to focus on testing for,develo"ing and using resistances that ma! be able to hel" thwart both current and new, un'nown

challenges. Cross/resistance, i.e. resistance against man! classes of "ests or diseases 0e.g.

#ndrew et al ., 34452, if it can be identified and tested adeuatel!, ma! have the most utilit! in

the future.

Ad/usting investments in molecular .iology and genomics research

)he enormous sums invested in molecular biolog! in man! countries, while being of greatscientific interest, must be better aligned with a""lied "rogrammes. )he surve! noted that

a""ro-imatel! =? "ercent of initiatives used molecular biolog! a""roaches. enomics

information is evolving at a ra"id "ace, and man! "roducts or tools will li'el! be of substantialinterest to breeders. For instance, it ma! become "ossible to narrow down the 'e! elements 0e.g.

families of genes2 o"erative in resistance, such as a com"ound from resin ter"enoid bios!nthesis

and "roduction, al'aloid e-"ressions, traumatic resin "roduction, formation of resin ducts or

"h!sical barriers such as bar' thic'ness or stone cells. 8owever, the largest challenge will be inma'ing the "ro"er lin'ages between mar'ers, gene e-"ression measures and the "henot!"ic

e-"ressions of the trait in large "edigreed forest tree "o"ulations, and then determining how tree

res"onses or traits affect "est or "athogen res"onse.

Populus trichocarpa cuttings being lifted in the

nurser! for research "lantings in field trials1 "o"lars

are widel! used in genomics and transgenics, but


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long/term basic field studies are still needed to

stud! natural levels of resistance and ada"tation toclimate change

#. ;anchu'

*ole of transgenic trees

)ransgenic technolog! can address some s"ecific "est "roblems tem"oraril!, but it still must beconsidered onl! one tool within well/develo"ed breeding "rogrammes. Because trees are "lanted

across landsca"es, and now because of the added com"le-ities that climate change will im"ose,

adeuate field testing over s"ace and time will be needed to ensure that gene e-"ression is stablewithin different genot!"es. 8owever, for short/rotation s"ecies such as "o"lar, it ma! be "ossible

to manage transgenic trees using a""roaches similar to those currentl! being used in agricultural

cro"s.

(!%%A*Y AN) #$N#!(I$N(

)he results of the surve! highlight three issues. First, since the $reaction time% for develo"ing

genetic o"tions for insect "est and disease resistance has t!"icall! been in the order of decades,

will this a""roach be useful in a world with ra"idl! changing climates& En the authors* o"inion, "robabl! not. )herefore it ma! be necessar! to develo" strategies that ma! "rovide some $"re/

em"tive% or general resistances.

Second, since there ma! be little or no lead time to 'now which "ests or diseases will "osethreats in the future, are there some better $generic% forms or classes of resistance that could bedevelo"ed in advance against various classes of insects or diseases& Et would be highl! desirable,

if "ossible, to identif! mechanisms of resistance that ma! be more affordable and allow for a

shorter turnaround and develo"ment time than at "resent.

)hird, will the resistance mechanisms currentl! being used be able to "rovide some "rotectionfrom new or related "ests and diseases&


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#lthough a more general t!"e of cross/resistance should not be e-"ected to be a t!"ical feature

of most resistance mechanisms 0Panda and Jhush, =DD91 Rii"i et al.,34492, it ma! now be

im"ortant to see' to understand the degree of variation "resent in currentl! selected elite "arenttrees ma'ing u" the seed "roduction and breeding "o"ulations. # reduction in the number of

genot!"es that researchers should and can afford to wor' with needs to be tem"ered with the

difficult! of accommodating more traits 0Verr!n, 344:2, "articularl! if negative geneticcorrelations are "resent between traits of interest. Moreover, resistance does not alwa!s incur a

"h!siological cost 0e.g. Jing et al.,=DD52, so mechanisms of resistance that are "ositivel!

correlated with growth would also be desirable ones to "ursue.

En summar!, after five decades of research on insect "est and disease resistance in trees,resistance breeding has had significant local im"acts1 however, the successes are largel! for a

few of the main commercial "rogrammes which have had substantial resources and structures in

"lace to deliver the gain.

En the future, funding agencies and researchers ma! need to focus declining resources and

research ca"acit! on s"ecies for which silvicultural o"tions to mitigate losses to insect "ests anddiseases are few. Research should also be focused on genot!"es that are alread! in tree

im"rovement "rogrammes or that could form the basis of a "rogramme.

Better alignment of forest genetics and forest health research "rogrammes will be reuired iftraditional tree im"rovement "rogrammes are to ca"itali+e on "ast investments in insect "est and

disease resistance research and hel" mitigate the "roected negative im"acts of climate change on

forest "roductivit! and health. )his is li'el! to become im"erative with "roections of increased "est and disease ris's in the future.

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Tree improvement programmes for forest health.docx