And, as the group sat there amid the Labl, ebean boles of these b e a u t i f u l hybrid larches, our tour was brought to a fitting close by some well-timed words of wlsdsm and caut ion from Ern%@ Schreiner, about what we can reasonably expect grona genetic gain in forest tree breedingG

I have deXibe~a&ely, and perhaps somewhat a r b i t r a r i l y , chasen to present % h i s hers in Dunkeld Larch No, 19---.at the end of a field tour during which %he Ln-

superfori%y sf the named trees has been pointed o u t , beginning with t h e nd ending here wieh t h e GEAm in 19 (ffguse I),

b s k aroma% you, There a r e f ew trees in this plantaeion of DunkeBd hybrids preach the growth-rate and $ o m sf the G I B W , Perhaps t h i s f s f o r t i t k ~ o u s ~

the GIANT i s a seedlfng an a single micro-site, we cannot be sure t ha t it is y S U P B ~ P ~ O F to some of the f i n e L r s e s in this stand, But if, BS we suspect , , is an exceplisraal genotype, w e canno% hope to use t h f s tree as a parent

productfon o f gezstically improved seed for comercfal use wStIt%.ou$ adultera- % i t s inherent potential,

fntent i s not &s diseuss expected genetie gain in gmproved seed-reproduced es, but ra&her to poin& o u t once more $hat the multiplication

re a sexua 1 propaga t $onc

FOREST TREE BmEDIHG

tree improvement programs $00 often have been narrowly o r i e n t e d toward n and breeding within a siwle na$%ve species,

f%d species; their $oanda&%on stocks were ancient mixtures whose ances t ry en to debate, And to these stocks $hey are s G f l l adding w i l d types for of par tecu la r charae&eris%f cs

ystem 02 pedigree breeding, including both %n&ra- and intesspecfffc 11 probably eontinue to be the methad moat gene~ally used for the genetie of forest %reese Pabreeding, where possible, uswlly provides the most o intensify and f i x inheren$ charactes%sties and to dezemine the mode

Baekcross breeding a lso i s highly e f f ec t i ve for de%ermfn%ng %he tanee, and for $ransferr%ng one ar two s%mpPy fnherfted characters to

desirable type,

ge, Forest Genetics Research, Ns~theastern Foreat Experiment Station, vtee, Durham, Mew &%fapsh%re, The Sorest genetics work is in eospera- " v e r s i t y sf Wew Hampshire,

- 7 -

However, i$ is becoming more and i:ot 2 a p 3 a r ~ 2 " - 1: 9-Y prz = l i - . . a i ~grrcultural ***w>-:j2-4J:a ;<>:;- - T p - 9 trap breeding and from $guaa%it%rtive gsr;at$cs z%at 19: % , r,, i m p r ~ e - i ~ .

of forest trees i " t ; i P 1 be necensh r-,- ";> $31 &:G : ;- zas > - ,.iwZ: 3 :mi- ; reeding systems (appropriate to the geu:rs) sr; ioos -3s 2ni:lbie. * a - " i"riliminaLcj

B i.

&he need for individua l-pedigree b~=eedb,r~,g 2a 1x2 r c cd k i s i - -,*18 SO forZ?1),

F igure 1.--Csoxrox Forest, The GMhT XN :48. 13.. i cz*c as 6 2-8 seedling in November, 1935, A f t e r 30 growing $9&L-83Lc* L,J t , ~ zSree as 14,4 inches &I,b,h , ; 76 f e e t t a l l , This is f roa Seed :-,!" P 7 , a,- g9 t q b r i d - larch "from the o r i g i n a l station, Dunie ld ~i Y - ~ . ? 5 i e i - 2 .

> d The sca r s on t h e tree to t h e left are r r t r , : cs~: ";- c;%g+:::g from b'lw-downs during the g r e a t w i n d of 1955, (1Pk5tf3 ~ 3 ~ : ? * < t- -anzl;ers. )

.w- t o r nany years I have srsessed t h e importance of the +:Lone for forest tree im-- provement, and the need f o r basic research to d e v e l o p economical methods for c l o n a l prcpagatlon of forest trees on t h e i r own roots (Schre iner 1939, 1957, 1960, 1963b, 2963~ 1 The a lmost phenomena l economic importance of h y b r i d poplar i n northern Italy exemplifies t h e advantages fo r r a p i d genetic improvement if superior genotypes can be utilized c r m e r c i a l l y a s clones

The introduction of the American cottonwmd ( del toides) i n t o the Po Val ley in n o r t h e r n I t a l y about l790, and of the ol l a t e r , set t h e stage fo r extensive n a t u r a l hybridization w i t h the native black poplar (g By 1928, when epidemic s p r i n g dieback--and to a lesser degree leaf rus t - - - th rea tened to eliminate profitable poplar culture. innumerable n a t u r a l hybrids were avarlable t h rowhou t the Po V a l l e y , T h i s n a t u r a l hybrid pspulatioa, the product of a 100 or more y e a r s o f n a t u r a l crass-breediw, represented m n y k i n d s and degrees of intercrosses between h y b r r d s and backcrosses, p a r t i c u l a r l y to the

nally abundant &

The present profitable poplar c u l t u r e in n o r t h e r n I t a l y i s a t t r i b u t a b l e in barge sure to c lona l selections from open-pollinated progenies sf super io r phenotypes of s n a t u r a l hybrid population, made by t h e l a t e Profassor Piccarolo and h i s a s s ~ c i - at the I n s t i t u t e for Poplar Research a t Casa Le-Monferrato (Sck re ine r a9591 In a r l y years t h e I n s t i t u t e grew more than 28,008 seedlings per yeas for n u r s e r y tion, In some yea r s as many a s BW,000 The most vrgorous seedlings t h a t were & a n t to sprlng d i e b a c k l e a f rust and other drseases were tested for rooting ty A f t e r 2 yea r s the very best from t h e standpoint o f growth v igor , disease

rooting ability and tree-fom were p l a n t e d i n a select ion arboretum and i e d for 10- to 20-year c l o n a l tests in. plantations es tab l i shed by cmperadors e landgwners) in va r fous localitses Severa l samets of a clone were p l a n t e d

tation, and a s the trees reached merchantable s i z e t h e best clones p lo t s have been selected f3r commercial planting. E t shou ld be noted t b t ntations have been a source sf profs t to the landowners w h i l e these clones

need for cheap methods of ~Ienal propagadlon sf a l l a g r i c u l t u r a l p l a n t s has rongly advocated by Twanley and C h r a s t i e (1964) . The f s l % s w ~ n g q u o t a t i o n s e l r paper 3te most pertinent to this dlscwssisn

e mos* exasperating and f l . u s t r a t fw expesJ-renees t h a t p l a n t s r l d over commonly encounte r is their i n a b i l i t y to capitalize

heaply on t h e r e a l l y superior gemplasm t h a t passes through hands T h i ~ s f t u a t i e n i s eonfined to as one crop and t o no one ing asth~d but r a t h e r i s common ro sll,"

ir example of a l f a l f a a cross-pollinated perennial b n s b i e h t h e very best n o t b2ing u t i l i z e d should be of p s r t i e u l a r interest to u s a s we sit

s f e w superior i n d i v i d u a l s r n t h i s h y b r i d larch plantation, par-

n % y in a l f a l f a b u t r n a l l crops belonging d s this breeding cype, i o n is even more exasperating' &re indeed muss be t h e forage in the course s f hss work has n o t run across a f ~ w s n d i v f d u l toad out amng their fellows as a g i a n t among men- The p l a n t kratlng i n a b i l i t y to capf ra l i ze on Ph i s unique gemplasm l i e s

sources T h e p l a n t owes f ts s u t s t a e d i ~ superiority do a rare corn- on of genes many of whsch a r e in t h e heterozygous s t a t e I n t h e

- 9 --

prwess of meiosis Lh%s superb cmbimt'on 13 broken j~p, pmbably never again do be reconstituteds In a d d i t i o n , t h e p % w ? ~ t s wi th which this out- s t a n d i ~ i n d i v i d u l is forced ha mate fo r t h e smxiuctlan of o f f s p r i n g are bomd to be inferior to it And sa , i ~ s t e a d sf being able to cap i t a l i z e fully on t h e r ea l l y superfor gsrnn1a .s~ aL W e disamal t h e iorage breeder is Bomed first ta sha t t e r it and t h e 3 to df Itate i t , Me t h u s ends up w i t h a v a r i e t y con ta i a$q a popufatlan &bat i s variable i n y i e l d , m t u r i t g , parsfstance, d i s a s e r e s i ~ t a a c e , seed pra4ue%ion, s l c e t e m , and not par-

e

t k c u l a r l y o u t s t a n d i w in any one of then

' Inen t h e technique o f induc ing spomlxls at w1.LI is developed--as it will be by smmne in tbe not too f a r distant future--the revolution that o c c u r r d i n corn production with t h e advent of the double cross s y s t e m w i l l be repeated, no t in one species, but %a every crop species in e x i s t - ence and in some synthetic species not get in existence, When this happens, when o u r suwrisr gemplasm is utilized i n s t e a d 0% d i s s ipa ted , two p l a n t breeders' dream rlll cme t r u e - "

S % KYBRLR VARIETIES

A$ present there a r e few forest trees t h a t c a n be propagated as clones f o r csmeseial p l a n r i q . Nevertheless, 1 pred ic t t h a t ~s can and ~ 1 1 2 develop practical me5hods for c loml pmpagation sf our important forest trees %n order to speed and mintain maxim;m improvement through what 5 have cel led "synthetic multiclonal hy- brid v a r i e t i e s in a su rg paper f o r t h e Proceedings of the NAm and NSF Advanced Study I n s t i t u t e on Genetic Impmvment f o r Disease and Pnseet Resistance sf Forest tree^, held a t The Pennsylvan%a State Unfvgrsfty in 1964 (Sehseiner 19661, These are ~nnlogous to, but genetically :iff erent f rorn t h e "mulilineal hybr id var ie t ies" and t h e "synthetic corn varieties.

A a p t h e t i c multielonal hybrid v a r i e t y would be a sufficiently s i m i l a r in their growth rqt-aabrernenb to be grown

in random m;ixturea, The breediw spatem to sbtala muBtfelona1 hybrid va r i e t i e s should Pollgbar %he same genera l pattern 02 selective intraspeeifie braeding, species c bgbrfdizatim, contm1Ped s g b - and backerossss, and recurrent mss selection a s fsr f

the development o f s v l h e t i c mrietbss Lo be propagazed Bg seedc But there would be a difference i n t he nursery procedure and the 2

The selected seedlings iF1 and l a t e r generations) would be released from eom- petition and grown in the nu r se ry beds, or pre fe rab ly in a t r a n s p l a n t n u r s e r y , long enough to p s d u c e enowh ramets for replication of at Peast 2-tree c lona l p lo t s in several regional progeny tests, ThPs would i ne reass t h e s i z e of the pmgeny test p l a n t a t i o n s , b u t they qould then become not only p rweny t e s t s but a l s o c l o n a l tests and by proper roguiw, gens pools sf s!~pesior genotypes. These gene pools w m l d be $he source 02 superior clones fo r use fn t h e synthetic au l t i e lom1 hybrid va r i e t i e s and P s r continuing i nd iv idua l - and %ass-pedigree breeding,

men n e c e a s a q , the clones fn a wulbichana3 hgb~fd v a r i e t y cou ld be c h n g e d on v a q sbr t notice, because %he breeder could multfplg superfor genotypes for cornier-

elmes in a smthetic multiclsnal hybrid var ie ty began to lose their va%de, due to incrmsiw diseaee or Bnaect s u s c e p t i b i P i t g , l a c k oi loca l a b p t a b i l i t y , d e c l i n e of gens=$ fitness due to l o n g - k e r n c l i m t i e changes, or to change in P n d u s t r i a l use

could be replaced by asa clones selected from t h e appmpria te

The gene t i c Improvement of c lones s e l e c t e d f o r c o m e r c i a 1 use can be es t imated d i r e c t l y from t h e c l o n a l m?ans' broad-sense h e r i t a b i l i t y ( c l o n a l h e r i t a b i l i t y ) is n o t needed I f f h e d a n e s are to be used f o r c o n t r o l l e d breed ing t o e s t a b l i s h new lines, t h e n h e r i t a b i l i t y i n t h e narrow sense may be u s e f u l .

ESTIMATE OF Tim REQUIRED FOR G a F T X C lMPRW

Following i s a n e s t i m a t e of t h e t i m e r equ i r ed t o complete one breed ing c y c l e i n t h e produetion of synthetxc seed v a r i e t i e s and t o produce f i r s t - c y c l e o r t e t s f o r ~ o m m e r e i a l p ropaga t ion of s y n t h e t i c m u l t i c l o n a l hybr id v a r i e t i e s .

S y n t h e t i c V a r i e t i e s f o r Propaga t ion by Seed

Depending on the growth r a t e and r ep roduc t ive h a b i t o f t h e s p e c i e s , t h e inher - e n t c h a r a c t e r i s t i c s or q u a l i t i e s t o be improved, and assuming t h e a v a i l a b i l i t y of a sufficient number of pa r en t trees t h e time r equ i r ed f o r reasonably e f f e c t i v e s e l e c - tian of p a r e n t s f o r t h e first c o n t r o l l e d s i b b i n g and backcross ing (one breed ing cycle) might be a p p r o x i m t e l y a s fo l lows:

From o r i g i n a l p o l l i n a t i o n to seed 1 t o 2 y e a r s

Nursery s c r een ing 1 t o 4 y e a r s

Eva lua t i on of p rogenies and i n d i v i d u a l s i n t h e r e g i o n a l progeny tests 8 t o 2 0 y e a r s

T o t a l time r equ i r ed f o r complet ion of one breed ing c y c l e SELETION OF PARENTS

R O W SIBBING AND BACKCROSSING, OR FOR MASS-PmIGREE BWEDING 10 t o 26 y e a r s

S y n t h e t i c M u l t i c l o n a l Hybrid V a r i e t i e s

On t h e s a m e assumptions a s above, t h e t i m e r equ i r ed t o produce improved, l o - I l y adap t ab l e , o r t e t s f o r commercial p ropaga t ion a s m u l t i c l o n a l hybr id v a r i e t i e s Om t h e first breed ing c y c l e might be approximate ly a s fo l lows:

From o r i g i n a l p o l l i n a t i o n t o seed 1 t o 2 y e a r s '

Nursery s c r e e n i n g and propaga t ion of s e l e c t e d o r t e t s f o r 2 - t r e e c l o n a l p l o t s i n r e g i o n a l progeny tests

Eva lua t i on o f c l o n e s i n t h e r e g i o n a l progeny L e s t s

u i r e d t o produce FIRST-CYCLE m T I C m A L HYBRID VARIEZIES

RCUL PROPA("IPIT"1ON

3 t o 7 y e a r s

6 t o 15 y e a r s

10 t o 24 y e a r s

T h e passlb: f itiie sf m a l . - i ~ lona l hybr~d v a r i e t i e s f o r ~ a r l y i~qprovement thsowh r h o use ?f unaduiderated s u p e r l o r genotypes, and f a r continaeus, pracLical%y a h n u s l , P - e x k b i l i t y 02 the c l o n a l m i x f i ~ e s to meet c h w i n g condrtrons, bring me a g a i n t o r h e need f o r research on the vegetative oropegation o f forest t rees

P l a n t s @;;an be propagated v e g e t a t i v e l y in many w a y s gueh a s g r a f t a g e , cuttage, end v a r i o u s l a y e r i n g methods I n c l u d i n g a i r - l a y e r i n g A 1 1 fo res t trees can be g r a f t e d , and $bey can be propagated w i t h v a r y i n g succe-ss to produce p l a n t s on their own roots C l o n a l propagation ( a n e l u d i n g g s a f ting) I A :.,%I 1: cc4n-r-ldesed too expen- sive fo r t h e p r o d u c t i o n sf Borest: planting stock of a l l bu: a very d e w c o m e r c i a $ l y ~ r n p o r t a n t timber t rees* For a specialty crop such as Ch~- rn - . - t 3a~ trees, the u s e o f g r a f t e d p l a n t i ~ stock may be eesnomicaliy f e a s i b l e (Scnrznnar 1963b).

G r a f t e d s t o c k has been used for varlaus aspec t3 9" B o w s t xree improvement research, If grafted trees a r e used e a * h e s for ressarc? cr f o r commercial Bares t planting, there must be a s s u r a n c e t h a t t h e rootsrock :jses not have a direc t or in- t iasect e f f e c t on the scion T h e r e a r e m a r y rs-$erenee:: :. 3 ti-? p l a n t science literr- a t u r e on the e f f e c t 0% the s tock on the s c i o n Awad and hexiworthy 499631 have reparted t h a t significant differences in l e a f compasix~ur: between trees on different roatstseks were ob te fncd Bsr K, B, @a, Mg, and Cu Ps~:ng and 5 l s s n (1963) from their s tud ies o n eight sc ion-rmls tack orebards exposed r o a severe freeze i n J a n u a r y 1962 i n t h e R i o Grande Valley, reported that r e T t a - " mandar l in rootstocks i nduced more cold k a r d i n e s s than o t h e r r s s t s t o z k s w h e ~ " , sec t $0. r"~sr catrus eb8nese

For both research and pr~ctf ee w e need r9 ddee-iop ec-c~e:o;aj P"'; 4 CF : 'la?s f o r c l o n a l propagation sf a l l P m p c r t a a n t forest t rees on %he? - Cjwn nxcmds J am con- ;?lnced t h a t this will be possible, S u t % d o u b ~ :&at xd;tle answer will come b y con- tinuing t h e pas t and much sf the pre sen t empir ica l approach t h i s problem requires fundamental research,

FOP t h e pines the answer may cone th rough rooting needle i s s c a c l e s T h i s method i s no t new' an o l d p,-.epagatcs~ at The sew Y9rk B Q ~ & P , % C & 1 G;-5rden, who wss r~e~ t i rag f a s c i c l e s in the e s r l y 1920 n, t o l d me t h a t he l e a r n e d the vethod as a young a p p r e n t i c e I n Europe* A p r i m a r y difficulty in production as =the dormancy of t h e buds below the t e r m a n a l f a s c i e 3 e s s T h i s dormancy be ing ~nvestigated i n s eve ra l c o u n t r i e s

The p r o d u c t i o n of cuttings far scionwood) poses a problem f o r ~ P o n a i propaga- tion of conifers to which experience w i t h s h e a r i n g 0% Scotch ;>ice C h r i s t m a s t r ee plantations t o produce r n u l t l p l e shoots m y p r o v i d e a n a n s w e r * Annual shea r ing sf wideby spaced mtker trees c o u l d provide a t l e a s t 50 80 100 c u t t i n g s (or scions$ per y e a r a t 6 to 10 years o f age , lMB such trees would produce 5,080 to 10 ,800 per year, If, eventually, needle-fascicles a r e used a s cutting-stock f o r c lona l psopa- gation, small, c l o n a l "mother-blocks" wl ll supply e l a rge amount of propagating m a t e r i a l ,

And a s a f i n a l recomendar isn f o r bas ic research on c lona l pmpagakion of genetieally supe r io r forest t rees, X urge ~ n v e s - t i g a t i a n of methods to utilize apsmixis (agamospemy). r e p r o d u c t i o n by seed w8thsu-t festiE~zation Al though a l a rge amount sf PiteraZure on apo rn ix~s in p l a n t s has accumulated d u r i n g the p a s t 100 y e a r s , very l i t t l e o f t h i s has concerned forest t r ees* TQO broad avenues sf approach shou ld be investigated: (1) t h e induction a f agarnospermy i n forest trees %ha t no rmal ly reproduce sexuallv; ( 2 ) a n i n t e n s l v c s e a r c h for genes t h a t c o u l d be used i n breeding f o r agarnospermy*

The second approach is being followed most i n t ens ive ly by forage b reede r s , e had consSderable success wieh buf fe lg ras s i n &he development of breeding

gh u$%lxziw genes fo r apomixis that w i l l p e r ~ t &he economical product5on o f f ,

%he bas i s o f present knowledge, &he seetoinid approach, the search f o r apomic- in&&viduals far use i n f o r e s t t r e e breeding appears more promising, pa s l i cu%ar%y

broadleaf species, than fnductf on of agarnospermy h r breeding work wi th $he Pate 1938 s ind ica ted such p ~ s s f b f l f t i e s Allen (1942) reported %ha%

T h a s dafa was l%mf%ed 1% did i n d i c a t e t ha t parehenogenesis* although un- i s psssSb%e in Douglas-fir*

LITERA CXTm

enocarpy, parthenogenesis , and s e l f - s t e r i l i t y of t r y 40: 642-644-

Kecworthy 1963 Clonal rm%s%ock and scion i n f lu- leaf e o n p ~ s i t i o n ~ Amerr Soc- Hort Sci, 83 : 68-73- R e Christie* 1964 Super ior gemplasm going Lo was&e or

eeder" dream become a r e a l f t y - Can, Depk Agr i , Res* B r a

X93gC The p o s s i b i l % % i e s of the c lone in f o r e s t r y Sour Forestry

959 Production of poplar t imber i n Europe and i d s s i g n i f i c a n c e n in the United S t a t e s * U. S, Dept A g r . , Agr. Handbook 150,

tives of pes t - r e s i s t ance improvement i n f o r e s t trees meat* 5 th World Fores t ry Gong, Pro@= 2 : 721-727

63aa Some sugges t ions for plus-&re@ s e l e c t i o n and seedling t Fores t Tree f mprove, Conf , Proc PO (1962 6 53-68 e c t i o n and breeding i n Christmas %see pxeduetion.

Growers' Jou r 7(1): 50-51* Xmprovement 09 d i s e a s e r e s i s t a n c e i n Populus* FAOIFBRGm-

Future needs f o r maximam progress in gene%%@ improvement of n forest trees, Breeding Pest-Resda%ant Trees Besgamon 455-466, (Proeeedfngs o f a HATO and NSF Symposiun, State

3963. Freeze i n j u r y t o c i t r u s trees sn var ious io Grande Valley of Texas, Amere Sees Hart* S c i