Theor. Appl. Genet. 50, 3-15 (19777

9 by Springer-Verlag 1977

Growth and Cold Hardiness of Intervarietal Hybrids of Douglas-fir G . E . Rehfeldt R e s e a r c h G e n e t i c i s t , I n t e r m o u n t a i n F o r e s t and Range E x p e r i m e n t Station, F o r e s t S e r v i c e , U.S. D e p a r t m e n t of A g r i c u l t u r e , Ogden, Utah ( U . S . A . ) S u m m a r y . P o t e n t i a l s for i m p r o v e m e n t of the i n t e r i o r v a r i e t y of D o u g l a s - f i r (Pseudotsuga m e n z i e s i i v a r . ' g l a u c a ' ) by h y b r i d i z a t i o n with the c o a s t a l v a r i e t y (P.m. v a r . ' m e n z i e s i i ' ) w e r e e x p l o r e d . The p r i m a r y o b j e c t i v e was to a s s e s s p o s s i b i l i t i e s for i n c r e a s i n g growth p o t e n t i a l s of the i n t e r i o r v a r i e t y while m a i n t a i n i n g a d a p t a t i o n to r e l a t i v e l y cold i n l a n d e n v i r o n m e n t s . Seventy f u l l - s i b h y b r i d f a m i l i e s and t h e i r h a l f - s i b p a r e n t a l l i n e s w e r e g r o w n in two c o n t r a s t i n g e n v i r o n m e n t s c o m m o n to the i n t e r i o r v a r i e t y . Nine t r a i t s r e l a t e d to growth, phenology, and f r e e z ing t o l e r a n c e in 4 - y e a r - o l d t r e e s w e r e c o m p a r e d . F o r t r a i t s r e l a t e d to growth (height and d i a m e t e r ) in the i n l a n d e n v i r o n m e n t , h y b r i d s e q u a l e d the growth of the c o a s t a l v a r i e t y and e x c e e d e d the i n t e r i o r v a r i e t y by 40 p e r c e n t . F o r t r a i t s r e l a t e d to adaptation (bud b u r s t , bud set, f r o s t d a m a g e , t r e e f o r m , and f r e e z i n g t o l e r a n c e ) , h y b r i d s w e r e i n t e r m e d i a t e but a p p r o a c h e d l e v e l s c h a r a c t e r i s t i c of the i n t e r i o r v a r i e t y . S u r v i v a l of h y b r i d s e q u a l e d that of the i n t e r i o r v a r i e t y and was s u p e r i o r to t h a t of the c o a s t a l v a r i e t y . H y b r i d c h a r a c t e r s could not be p r e d i c t e d r e l i a b l y from those of p a r e n t a l l i n e s . Yet, q u a n t i t a t i v e g e n e t i c a n a l y s e s s u g g e s t that e x p r e s s i o n of c h a r a c t e r s r e l a t e d to growth depends on n o n a d d i t i v e g e n e t i c effects, but e x p r e s s i o n of t h o s e r e l a t e d to a d a p t a t i o n i s s o m e w h a t dependent on additive e f f e c t s . R e a l i z a t i o n of the t r e m e n d o u s potential of h y b r i d i z a t i o n for i m p r o v e m e n t of the i n t e r i o r v a r i e t y will r e q u i r e at l e a s t one b a c k c r o s s g e n e r a t i o n o r additional c r o s s e s u t i l i z i n g i n t r o g r e s s e d p o p u l a t i o n s . Key w o r d s : Pseudotsuga menziesii - D o u g l a s - f i r - H y b r i d i z a t i o n - Cold H a r d i n e s s - P h y s i o l o g i c Adaption Growth P a t t e r n Introduction

tish C o l u m b i a , growth of i n t e r v a r i e t a l h y b r i d s is i n f e r i o r to that of c o a s t a l p a r e n t a l l i n e s ( O r r - E w i n g

I n t e r v a r i e t a l h y b r i d i z a t i o n of D o u g l a s - f i r (Pseudo-

1966; O r r - E w i n g et al. 19727. Yet, t h e s e s a m e h y -

tsuga m e n z i e s i i ) p r o v i d e s a m e a n s for i n c o r p o r a t i n g

b r i d s m a y be c o n s i d e r a b l y m o r e v a l u a b l e to i n l a n d e n -

the growth potential of the c o a s t a l v a r i e t y (P.m. v a t .

v i r o n m e n t s than to m a r i t i m e e n v i r o n m e n t s ( O r r - E w i n g

' m e n z i e s i i ' ) into the g e r m p l a s m of the i n t e r i o r v a r -

et al. 1972).

iety (P.m. v a r .

' g l a u c a ' ) . A d a p t a t i o n to a m a r i t i m e

The o b j e c t i v e of the p r e s e n t study is to e x p l o r e the

c l i m a t e ( F i g . 1) has endowed the c o a s t a l v a r i e t y with

potential of i n t e r v a r i e t a l h y b r i d i z a t i o n for i m p r o v i n g

growth r a t e s s u p e r i o r to the i n t e r i o r v a r i e t y . Yet,

D o u g l a s - f i r in the N o r t h e r n Rocky M o u n t a i n s . P r i -

s u p e r i o r growth p o t e n t i a l s a r e r e a l i z e d only in m i l d

m a r y e m p h a s i s i s g i v e n to growth p o t e n t i a l , p h y s i l o g i c

c l i m a t e s (Haddock et al. 1967; S o r e n s e n 19677.

and phenologic a d a p t a t i o n to the growing s e a s o n , and cold

W h e r e a s the i n t e r i o r v a r i e t y is adapted to the cold

h a r d i n e s s . However, s i n c e h y b r i d s m u s t withstand the i n -

w i n t e r s of the Rocky Mountain and I n t e r m o u n t a i n r e -

t e r r e l a t e d c o m p l e x of e n v i r o n m e n t a l f a c t o r s that c h a r -

g i o n s , the c o a s t a l v a r i e t y s u s t a i n s high m o r t a l i t y and

a c t e r i z e the i n t e r i o r , the n u m e r o u s additional t r a i t s

f r o s t d a m a g e in c o n t i n e n t a l c l i m a t e s of the United

t h ~ d i f f e r e n t i a t e the v a r i e t i e s c a n n o t be d i s c o u n t e d .

States ( W r i g h t et al. 1971; G e r h o l d 1965; B a l d w i n

In addition to c h e m i c a l d i f f e r e n c e s a s s o c i a t e d with m o n o -

and Murphy 1956) and G e r m a n y ( S t e r n 1974). In r e l -

t e r p e n e s (yon Rudioff 19737, the v a r i e i t e s differ in

a t i v e l y cold i n l a n d e n v i r o n m e n t s , h y b r i d i z a t i o n m a y

a b i l i t y to withstand drought ( F e r r e l l and Woodard

e f f e c t i v e l y i n c r e a s e the growth potential of the i n t e r -

1966 ; P h a r i s and F e r r e l l 1966), in p a t t e r n s of growth

i o r v a r i e t y while m a i n t a i n i n g cold h a r d i n e s s . Although the concept of h y b r i d i z a t i o n for i m p r o v e -

( I r g e n s - M o l l e r 1968), and in t o l e r a n c e to Rhabdo-

c l i n e pseudotsu~ae (Stephan 1973). T h e r e f o r e , the

m e n t of D o u g l a s - f i r was s u g g e s t e d long ago (Duffield

p r e s e n t r e p o r t of the growth and the cold h a r d i n e s s

19507, c u r r e n t effort e m p h a s i z e s i m p r o v e m e n t of the

of 4 - y e a r - o l d h y b r i d f a m i l i e s and t h e i r p a r e n t a l l i n e s

c o a s t a l v a r i e t y . In the m a r i t i m e e n v i r o n m e n t of B r i -

will be s u p p l e m e n t e d by field t e s t s .

4

F i g . 1. G e o g r a p h i c d i s t r i b u t i o n of D o u g l a s - f i r (Pseudotsuga mer~ziesii) and l o c a t i o n of p r o v e n a n c e s f r o m which h y b r i d s w e r e d e v e l o p e d . The b r o k e n l i n e ap p r o x i m a t e s s e p a r a t i o n of t h e two v a r i e t i e s P.m. v a r . ' m e n z i e s i i ' and p.m. v a r . ' g l a u c a ' ( f r o m Little 1971)

M a t e r i a l s and Methods In addition to 70 h y b r i d f a m i l i e s p r o d u c e d f r o m c o n t r o l l e d p o l l i n a t i o n s (Table 1 ) , w i n d - p o l l i n a t e d c o n e s w e r e o b t a i n e d f r o m t h e 15 t r e e s u s e d as p a t e r n a l p a r e n t s and t h e 18 t r e e s u s e d as m a t e r n a l p a r e n t s . Thus, t e s t s i n c l u d e d 70 f u l l - s i b h y b r i d f a m i l i e s and 33 h a l f - s i b f a m i l i e s that r e p r e s e n t e d p a r e n t a l l i n e s . S eed s w e r e sown in O c t o b e r 1971 in u n r e p l i c a t e d n u r s e r y beds at th e P r i e s t R i v e r E x p e r i m e n t a l F o r e s t N u r s e r y . D u r i n g the f i r s t y e a r of g r o w t h , t h e f o l lowing o b s e r v a t i o n s w e r e m a d e : (1) date on which 90 p e r c e n t of the s e e d l i n g s e m e r g e d , (2) date on which 75 p e r c e n t of t h e t r e e s s e t bud, (3) o c c u r r e n c e of chlorophyll-deficient and albino seedlings, (4 ) height of 50 seedlings of each family, (5) percent survival after the first winter.

Theor. Appl. Genet. 50 (1977)

Nursery trials were established with l-year-old trees at the Coeur d'Alene (Cd'A) and Priest River Experimental Forest ( P R E F ) Nurseries. For all families, five seedlings were transplanted at a spacing of 30 c m into row plots in each of two replications at both nurseries. W h e n seedlings were 3 years old, height was measured and d a m a g e from an early fall frost was scored. During the fourth season of growth, rate of bud burst, date of bud set, andtreeform were scored for each tree. Tree height, diameter at the ground, and leaf length also were measured. Frost d a m a g e to each tree was scored on 10 October by m e a n s of a s c a l e f r o m 1 to 3 : @ l = n o d a m a g e , 2 = i n j u r y to l e a v e s , 3 = d a m a g e to l e a v e s and wood. Bud b u r s t was s c o r e d 19 May at C d ' A and 2 J u n e at P R E F a c c o r d i n g to a s c a l e of 1 to 6 : ~ 1 = bud s c a l e s c l o s e d with no g r e e n l e a v e s v i s i b l e , 6 = e l o n g a t i o n to such an extent that new s h o o t s d r o o p e d p r o n o u n c e d l y . The d a t e b y w h i c h a l l b u d s h a d s e t on e a c h t r e e was s c o r e d at w e e k l y i n t e r v a l s . F o r m was s c o r e d on a s c a l e of 1 to l l : 1 = p r o n o u u c e d d o m i n a n c e of a s i n g l e l e a d e r , 7 = a m a j o r fork r e s u l t i n g in c o d o m i n a n c e of two l e a d e r s , and 11 -- no dominant l e a d e r . Where necessary, appropriate transformations were made for normalizing frequency distributions (Steel and T o r r i e 1960), and the following s t a t i s t i c a l a n a l y s e s w e r e m a d e on data f r o m n u r s e r y t r i a l s : (1) a n a l y s e s of v a r i a n c e f o r a s s e s s i n g the m a g n i t u d e of d i f f e r e n c e s am o n g and within p a r e n t a l v a r i e t i e s and t h e i r h y b r i d s , (2) q u a n t i t a t i v e g e n e t i c a n a l y s e s f o r h y b r i d f a m i l i e s , and (3) r e g r e s s i o n a n a l y s e s f o r p r e d i ct i n g t h e p e r f o r m a n c e of h y b r i d f a m i l i e s f r o m that of t h e i r p a r e n t a l l i n e s . A f t e r data had been c o l l e c t e d f r o m the n u r s e r y trials, artificial freezing tests were made for a s s e s sing d i f f e r e n t i a l t o l e r a n c e to c o l d of h y b r i d f a m i l i e s and t h e i r p a r e n t a l l i n e s . F o r both r e p l i c a t i o n s at e a c h n u r s e r y , l i g n i f i e d t w i g s f r o m the f i v e t r e e s r e p r e s e n ting a s i n g l e f a m i l y w e r e cut, m o i s t e n e d , p a c k a g e d t o g e t h e r in p o l y e t h y l e n e b ag s, and s t o r e d in a c o o l e r . This p r o c e d u r e was f o l l o w e d b i w e e k l y f r o m l a t e S e p t e m b e r to l a t e N o v e m b e r . Twigs w e r e t r a n s p o r t e d to the M o s c o w l a b o r a t o r y w h e r e they w e r e s t o r e d at 3 ~ E x c e p t f o r the s a m p l e s c o l l e c t e d in l a t e N o v e m b e r , all s a m p l e s w e r e f r o z e n at a c o o l i n g r a t e of 5 ~ to p r e d e t e r m i n e d t e m p e r a t u r e s within 36 h o u r s f r o m c o l l e c t i o n . As o u t l i n e d by Sakai and W e i s e r ( 1 9 73) , an a t t e m p t was m a d e to induce m a x i m u m h a r d i n e s s into t w i g s c o l l e c t e d in l a t e N o v e m b e r . Since t h e s a m p l e s had b e e n c o l l e c t e d at t e m p e r a t u r e s below 0 ~ t w i gs were stored at -7~ for i week and at -10~ for 3 days. Thereafter, they were cooled at a rate of 5~ to predetermined temperatures. Twigs were r e m o v e d from the freezer at the desired temperature, thawed at 5~ for at least 24 hours, and placed in water in a greenhouse. After I week, d a m age from freezing was scored on the basis of browning of leaves. The n u m b e r of twigs d a m a g e d for each family was recorded according to each replication at both nurseries. Regression analyses were used to assess d i f f e r e n t i a l a b i l i t y of f a m i l i e s to t o l e r a t e f r e e z i n g .

Results General Observations As a n t i c i p a t e d f r o m the r e s u l t s of A l l e n (1960, 1961), 90 p e r c e n t of the s e e d l i n g s r e p r e s e n t i n g t h e i n t e r i o r

G .E.

Rehfeldt : Growth and Cold Hardiness

of I n t e r v a r i e t a l

H y b r i d s of D o u g l a s - f i r

5

T a b l e 1. M a t i n g d e s i g n f o r p r o d u c t i o n o f 70 f u l l - s i b h y b r i d f a m i l i e s . F a m i l y c o d e s i n c l u d e d t h e h y b r i d s , 15 p a t e r n a l h a l f - s i b f a m i l i e s , a n d 18 m a t e r n a l h a l f - s i b f a m i l i e s . H y b r i d c o d e s a r e d e r i v e d f r o m t h e c o m b i n a t i o n o f codes that key their respective parental lines Maternal provenances,

Paternal provenance Tree number

interior variety

Lacomb,

Family Code Moscow, Idaho

Clarkia, Idaho

2 3 4 5 7 8 9 10

5 7 8 9 10

7 9 16 17 18 19 22 25 26 27

11 12 13 14 15 16 17 18 19 20

Oregon

curred

bino seedlings terior

100

100

101

102

103

104

98

99

100

106

107

A

B

C

D

E

F

G

H

I

J

U

V

W

X

Y

2B 3B 4B

2C 3C 4C

2D 3D 4D

2E 3E 4E 5F 7F 8F

9A 10A

9B 10B

9C 10C

9D 10D

llA

trees

12V 13H

13W 14I

14X

15E 16A

15J 16U 17G

18C

17V 18H

18W

19D

19I

19X

20E

b y 17 M a y a n d s e e d l i n g s

variety.

repre-

2 w e e k s l a t e r . The was the same

in three families

or al-

of t h e i n -

hy-

h a d s e t b u d s by 3 A u g u s t , respectively.

variety averaged

Whereas

5 cm in height,

and the coastal variety averaged 7.5 cm.

H i g h r a t e s of m o r t a l i t y

occurred

reached

during the winter

-26~

20J

when there was

20Y

buds only 1 week before nursery tests were established. Little additional 3 years,

No m u t a n t s e e d l i n g s o c -

Chlorophyll-deficient

a n d 26 S e p t e m b e r ,

15Y

16F 17B

were present

of 1 9 7 2 . T e m p e r a t u r e s

5J 7J 8J

llU

14D

of hybrid seedlings

of t h e i n t e r i o r

51 7I 8I

12G 13C

and coastal families

hybrids

5H 7H 8H

11F 12B

Seventy-five percent of the seedlings from interior, brid,

5G 7G 8G

9E 10E

variety and in two families of the coastal variety.

28 A u g u s t ,

B. C.

35

2A 3A 4A

in hybrid families.

Lake Cowichan,

11

senting the coastal variety emerged

as that of the interior

Oregon

10

4

r a t e of e m e r g e n c e

Valsetz,

8

2 3

variety had emerged

- coastal variety

occurred

during the next

a l t h o u g h it w a s n o t u n t i l t h e w i n t e r

that some depth.

mortality

trees

Yet,

were

these

taller

general

the capability

of hybrid

inland climate

approaches

As a group,

observations

families

suggest

to survive

that of the interior

hybrids were intermediate

ental varieties

in some traits,

variety in others,

o f 1974

than the maximum

similar

and approached

lelic or genic contributions

that

in the variety.

between parto the interior

the coastal variety

in still other traits. A lack of chlorophyll-deficient albino mutants in hybrid families

snow

and

implies unique al-

to t h e g e n e t i c l o a d of p a r -

ental varieties.

l i t t l e o r n o s n o w c o v e r . W h e r e a s 44 p e r c e n t of t h e t r e e s of hybrid and interior

origin survived,

of t h o s e o f c o a s t a l o r i g i n s u r v i v e d . survival

only 9 percent

Of t h e l a s t g r o u p ,

Nursery

Studies

was only 5 percent for trees from Oregon, but

w a s 20 p e r c e n t

for those from British Columbia.

Unfortunately, effects of climate ling survival.

it i s not p o s s i b l e to s e p a r a t e from those of transplanting

Many trees

Except for families the

on seed-

of c o a s t a l o r i g i n h a d s e t

the nursery replaced

from Oregon,

most seedlings in

tests that died during the first winter were

i n t h e s p r i n g of 1 9 7 3 . A f t e r t r a n s p l a n t i n g ,

five seedlings

represented

most families

in each rep-

6

Theor. Appl. Genet. 50 (1977)

l i c a t i o n at b o t h n u r s e r i e s , lings representing

each family from Oregon averaged

l e s s t h a n o n e in e a c h r e p l i c a t i o n . used for replacement may represent

iance within families. Depending on thevariable, these

but t h e n u m b e r of s e e d Because seedlings

survived the first winter, they

the most hardy individuals from each

family. Thus, particularly for coastal origins, plasm represented

in t h e n u r s e r i e s

toward maximal hardiness.

germ

effects accounted for 40 to 75 percent of the variance. Mean differences for traits relatedto growth (height and diameter) indicate that traits of the hybrids and the coastal variety exceed the interior variety by about 40 percent (Table 2). Infact, over 70 percent of the hybrid families were of significantly (LSD 0.05) greater

m a y be s k e w e d

P o s s i b l e e f f e c t s of a s k e w e d

height and diameter than the family representing its

d i s t r i b u t i o n on i n t e r p r e t a t i o n of s t a t i s t i c a l a n a l y s e s

maternal parent and about 25 percent were also larger

will be a s s e s s e d

than the family representing its paternal parent. For

subsequently.

A n a l y s e s of v a r i a n c e r e v e a l e d that t h e l a r g e m e a n

traits related to adaptation to the inland climate (bud

d i f f e r e n c e s f o r all v a r i a b l e s e x c e p t bud b u r s t at C d ' A

burst, bud set, frost damage, and form), hybrids

( T a b l e 1 ) w e r e a s s o c i a t e d with s i g n i f i c a n t ( 1 7o l e v e l )

were generally intermediate between their parental

main effects for varieties

representatives (Table 2), but comparisons of means

and n u r s e r i e s .

Analyses al-

so revealed substantial variation among families with-

(LSD 0.05) showed that a smaller proportion of hy-

in p a r e n t a l v a r i e t i e s and a m o n g h y b r i d f a m i l i e s f o r

brid families deviated significantly from their ma-

most variables.

ternal line than from their paternal.

H o w e v e r , e x c e p t f o r t r e e f o r m and

r a t e of bud b u r s t ,

intraclass

correlations

for varieties

Similarities in results for several variables are

w e r e 2 to 5 t i m e s g r e a t e r t h a n t h o s e a s s o c i a t e d with

elucidated by the correlation matrix (Table 3 ). First,

families within varieties.

trees that set buds late tended to suffer frost damage;

tween nurseries two variables. intermediate

Significant interactions be-

and v a r i e t i e s w e r e d e t e c t e d f o r o n l y F r o s t d a m a g e to h y b r i d s at P R E F w a s

b e t w e e n t h a t of t h e two v a r i e t i e s .

high levels of frost damage poor form growth

At

were

associated

(high score) ; trees of poor form

rate (negative deviation from

with a had a low

the regression

C d ' A , w h e r e d a m a g e w a s m u c h l e s s s e v e r e t h a n at

line) ; and low growth

PREF,

Second,

tall trees tended to have large diameters,

leaves,

and a high growth

h y b r i d s s u f f e r e d t h e s a m e l e v e l of d a m a g e a s

the interior variety.

B u d b u r s t at C d ' A o c c u r r e d

a p p r o x i m a t e l y t h e s a m e t i m e f o r all v a r i e t i e s .

at

fall to represent

At

rate characterized

short trees. long

rate. Yet, these coefficients

character

association

within the di-

P R E F bud b u r s t f o r t h e c o a s t a l v a r i e t y w a s d e l a y e d .

vergent varieties. Underlined coefficients (Table 3 ) re-

High i n t r a c l a s s

flect associations

Table 2. Mean

correlations

were associated with vat-

values for eight variables

according

to nurseries

(5 ~ level)

and varieties

Frost d a m a g e ( c l a s s e s ) Height Leaf deviBoth l e n g t h ation~ nurs(mm) (cm) PREF 3 Cd'A 4 eries

Bud burst (classes)

4.00

4-year height (cm)

Diam- Bud eter set • (mm) (weeks)

50.2 57.2

12.3 15.9

3.8 2.6

5.9 3.9

31.8 30.4

-1.11 +1.11

33.9 54.1 53.2

10.0 14.0 13.6

2.1 3.1 4.3

4.2 4.4 6.2

30.3 31.5 29.2

-I.05 1.08 + 1 . 0 2 1.63 -1.04 2 . 2 3

Form (classes)

that differed significantly

PREF

Cd'A

Nurseries PREF Cd'A

1.62

3.78

1.04

Varieties Interior Hybrid Coastal

W e e k s after August 1 2 Deviation from regression of 4-year height on 3-year height a Priest River Experimental Forest Nursery 4 Coeur d' Alene Nursery

1.00 1.04 1.33

1.04 1.33 1.72

4.17 4.02 3.56

3.67 3.69 3.90

G . E . Rehfeldt : G r o w t h and Cold H a r d i n e s s of I n t e r v a r i e t a l H y b r i d s of D o u g l a s - f i r

7

Table 3. S i m p l e c o r r e l a t i o n c o e f f i c i e n t s a m o n g eight v a r i a b l e s . C o r r e l a t i o n s w e r e b a s e d on data f r o m i n d i v i d u a l s e e d l i n g s f r o m all f a m i l i e s , n u r s e r i e s , and r e p l i c a t i o n s . S i g n i f i c a n c e at the 1 p e r c e n t l e v e l of p r o b a b i l i t y is i n d i c a t e d by r > 0 . 0 8 and r < - 0 . 0 8 . U n d e r l i n e d c o e f f i c i e n t s r e f l e c t a s s o c i a t i o n s that d i f f e r e d s i g n i f i c a n t l y in p a r e n t a l v a r i e t i e s Variable Frost damage Bud burst Bud set Form Diameter Height Deviation ~ Leaf length

4-year height

Frost damage

Bud burst

Bud set

Form

-0.05 -0.04 0 -~.12 0.87

0.05 0.38 0.29 -0.14

0.03 0.08 -0.11

0.30 -0.08

-0.01

0.51 0.33

-0.37 0.II

-0.01 0.01

-0.08 0.I0

-0.36 0.07

Diameter

Height deviation ~

0.39 0.31

0.06

1 D e v i a t i o n f r o m r e g r e s s i o n of 4 - y e a r height on 3 - y e a r height

f o r p a r e n t a l v a r i e t i e s . All of t h e i n d i c a t e d a s s o c i a t i o n s p e r t a i n to e i t h e r d i r e c t o r i n d i r e c t r e l a t i o n s h i p s with

C o n t r a s t i n g g e n e t i c e f f e c t s d i f f e r e n t i a t e d the v a r ious t r a i t s . G e n e t i c e f f e c t s a c c o u n t e d f o r l i t t l e v a r i -

bud b u r s t and bud s e t . Thus, d i f f e r e n t m a t r i c e s p r i m a -

a n c e in t r e e f o r m , height d e v i a t i o n , o r f r o s t d a m a g e

r i l y r e f l e c t the d e g r e e that p h e n o l o g i c a l e v e n t s of the

at C d % . G e n e t i c v a r i a n c e s f o r height and d i a m e t e r

c o a s t a l v a r i e t y w e r e o u t - o f - p h a s e with the i n l a n d c l i -

w e r e a s s o c i a t e d p r i m a r i l y with i n t e r a c t i o n s b e t w e e n

mate.

m a l e s and f e m a l e s . W h e r e a s s m a l l but s i g n i f i c a n t

R e s u l t s of t h e s e a n a l y s e s e m p h a s i z e g e n e t i c d i v e r -

m a i n e f f e c t s of f e m a l e s w e r e i n d i c a t e d by l e a f length,

g e n c e of t h e two v a r i e t i e s along with s u b o r d i n a t e g e n -

g e n e t i c v a r i a n c e in bud s e t was d e t e r m i n e d p r i m a r i l y

e t i c v a r i a t i o n within e a c h v a r i e t y . Yet, p a r e n t a l v a r -

by the m a i n e f f e c t s of m a l e s . That f o r f r o s t d a m a g e

i e t i e s a r e s u f f i c i e n t l y r e l a t e d that i n v i a b i l i t i e s , i n -

at P R E F and bud b u r s t was d i v i d e d b e t w e e n m a i n e f -

c o m p a t i b i l i t i e s , o r n e g a t i v e h e t e r o s i s w e r e not e v i -

f e c t s of m a l e s and f e m a l e s .

d e n c e d by the p e r f o r m a n c e of h y b r i d f a m i l i e s . In the

Additional a n a l y s e s w e r e m a d e a c c o r d i n g to t he

inland c l i m a t e , h y b r i d s e x p r e s s e d g r o w t h p o t e n t i a l s

following m o d el f o r a s s e s s i n g the r e l a t i v e i m p o r t a n c e

s i m i l a r to the c o a s t a l v a r i e t i y and a d a p t a t i o n a l f e a -

of m a t e r n a l l i n e, p a t e r n a l l i n e , and n u r s e r y e n v i r o n -

t u r e s that a p p r o a c h e d t h o s e of the i n t e r i o r v a r i e t y . A

m e a t in d e t e r m i n i n g h y b r i d p e r f o r m a n c e :

high d e g r e e of v a r i a t i o n a m o n g and within h y b r i d f a m ilies approbates quantitative analyses for elucidat-

Yi7 d = a + bXi9 + bXid + bX n

ing g e n e t i c v a r i a n c e s . E v e n though t h e o r e t i c a l c o n c e p t s in q u a n t i t a t i v e genetics for hybrid populations are r a t h e r limited, q u a n t i t a t i v e m e t h o d s w e r e u s e d f o r data f r o m the 70 f u l l - s i b h y b r i d f a m i l i e s . R e s u l t s of t h e s e a n a l y s e s s h o u l d p r o v i d e only a g e n e r a l a s s e s s m e n t of g e n e e f f e c t s , g e n e t i c v a r i a n c e s , and s e l e c t i o n p r o c e d u r e s f o r the h y b r i d f a m i l i e s . A l t h o u g h r e s u l t s of q u a n t i t a t i v e a n a l y s e s (Table 4) a r e p r e s e n t e d as if t h e m a t i n g d e s i g n had b e e n h i e r -

where: YiQd = m e a n v a l u e of h y b r i d of m a t e r n a l f a m i l y 9 and p a t e r n a l f a m i l y c~ g r o w i n g in n u r s e r y i. Xi~ = m e a n v a l u e of the h a l f - s i b f a m i l y r e p r e s e n ting m a t e r n a l t r e e Q in n u r s e r y i. X i d = m e a n v a l u e of the p a t e r n a l h a l f - s i b f a m i l y d g r o w i n g in n u r s e r y i. X

n

= dummy variable for nurseries.

A c c o r d i n g to t h i s m o d e l , r e s u l t s of a n a l y s e s a r e

a r c h i a l , the m o s t a p p r o p r i a t e d e s i g n i n v o l v e d s e v e n

s u b j e c t to b i a s i n t r o d u c e d by the confounded m a t i n g

s e t s of f a c t o r i a l m a t i n g s (Table 1 ) . S t a t i s t i c a l a n a l y s e s

d e s i g n . To a l l e v i a t e e f f e c t s of confounding, the r e l a -

and t h e i r i n f e r e n c e s w e r e m a d e a c c o r d i n g to beth d e -

t i v e i m p o r t a n c e of independent v a r i a b l e s in d e t e r -

s i g n s , but t h e h i e r a r c h i a l m o d e l is p r e s e n t e d f o r s i m -

m i n i n g t h e dependent v a r i a b l e was a s s e s s e d by m e a n s

plicity.

of s t a n d a r d i z e d p a r t i a l r e g r e s s i o n c o e f f i c i e n t s f o r

8

T h e o r . Appl. Genet.

50 (1977)

Table 4. I n t r a c l a s s c o r r e l a t i o n s d e r i v e d f r o m a n a l y s e s of v a r i a n c e f o r e x a m i n i n g p e r f o r -

S o u r c e of v a r i a n c e df Nurseries Replication Families .

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1 4 69 .

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Females Males/females .

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Form

0;06** 0.03** 0.17"*

0.20** 0.01" 0.16"*

0.17"* 0.01"* 0.08**

0.11"* 0 0.04**

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Experimental error s Within cells

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139 1,042

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0.18"* 0.56

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0.02** 0.02**

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0.04*

0 0.02

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0.0 0.04**

0.02

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0 0 .

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0.03** 0.05**

0 0 .

.

0.01 0.07"*

0

0 0 .

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0.01 0.15"*

0 0 .

.

0.01 0.15"*

0

14 55 .

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0 0.17"*

17 52 .

.

0.01 0.16"*

69

N x males N • females/males .

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.

N • females N x males/females .

.

Bud set

14 55

N • families

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.

Diameter

17 52

Males Females/males .

.

4-year height

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0.03** 0.01

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0 0.02 .

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0.09** 0.54

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0 0.04"

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0. I0"* 0.62

0.05** 0.75

D e v i a t i o n f r o m r e g r e s s i o n of 4 - y e a r height on 3 - y e a r height C o n t a i n s s o u r c e s of v a r i a t i o n f r o m t h e t h r e e i n t e r a c t i o n s i n v o l v i n g r e p l i c a t i o n * S i g n i f i c a n c e of F v a l u e at 0 . 0 5 l e v e l of p r o b a b i l i t y * * S i g n i f i c a n c e of F v a l u e at 0.01 l e v e l of p r o b a b i l i t y

which e f f e c t s of i n t e r c o r r e l a t i o n among independent

h y b r i d f a m i l i e s s e e m s to be dependent on n o n a d d i t i v e

variables are eliminated.

g e n e t i c v a r i a n c e s . Adaptational f e a t u r e s s e e m to be

R e s u l t s of r e g r e s s i o n a n a l y s e s (Table 5) depict an

d e t e r m i n e d by r e l a t i v e l y weak a d d i t i v e e f f e c t s . E x -

e x p e c t e d p r e d o m i n a n c e of n u r s e r y e f f e c t s in d e t e r -

cept f o r bud b u r s t , the p e r f o r m a n c e of m a t e r n a l and

m i n i n g h y b r i d p e r f o r m a n c e f o r m o s t t r a i t s . A l s o ap -

p a t e r n a l h a l f - s i b l i n e s p o o r l y r e f l e c t s the p e r f o r m a n c e

p a r e n t fo r all t r a i t s , e x c e p t f r o s t d a m a g e and bud

of h y b r i d f a m i l i e s .

b u r s t , is c h a r a c t e r e x p r e s s i o n in h y b r i d s that is i n dependent of that of t h e i r p a r e n t a l l i n e s . Although t h e s e r e s u l t s a r e s o m e w h a t c o n t r a d i c t o r y to the f o r e going, l i t t l e i n f l u e n c e of p a r e n t a l l i n e s c o u l d be e x p e c t e d in t r a i t s f o r which l i t t l e g e n e t i c v a r i a n c e o r n o n a d d i t i v e e f f e c t s w e r e p r o n o u n c e d in p r e c e d i n g a n a l y s e s . F a i l u r e of r e g r e s s i o n a n a l y s e s to c o r r o b o r a t e

Table 5. C o e f f i c i e n t s of d e t e r m i n a t i o n and s t a n d a r d i z e d partial regression coefficients derived from multiple r e g r e s s i o n s of eight v a r i a b l e s f o r p r e d i c t i o n of h y b r i d m e a n v a l u e s f r o m t h o s e of m a t e r n a l p a r e n t a l l i n e s , p a t e r n a l p a r e n t a l l i n e , and n u r s e r y e n v i r o n m e n t s

p a t e r n a l e f f e c t s i n d i c a t e d by p r e v i o u s a n a l y s e s m a y reflect either reduced penetrance of the coastal g e r m plasm in the inland environment or bias introduced from small samples of several paternal lines. Yet, both analyses support maternal effects for frost d a m age and bud burst. Regardless, except for bud burst, parental lines account for little of the variance determined by the regression models. Quantitative analyses show substantial levels of g e n e t i c v a r i a t i o n among h y b r i d f a m i l i e s . G r o w t h of

Variable

R 2

b '9

b 'd

4 - y e a r height Diameter Bud set Form Leaf length Height d e v i a t i o n Frost damage Bud b u r s t

0.09* 0.28** 0.33** 0.31"* 0.14"* 0.63** 0.75** 0.37**

0.08 0.11 0.18 -0.15 0.23 -0.01 0.25* 0.54**

-0.11 -0.05 0.18 -0.06 0.20 -0.01 -0.12 0.04

b 'N -0.33" -0.49"* 0.33** 0.69* 0.24** -0.81"* 0.80** 0.15

** S i g n i f i c a n c e at t h e 1 p e r c e n t l e v e l of p r o b a b i l i t y * S i g n i f i c a n c e at the 5 p e r c e n t l e v e l of p r o b a b i l i t y

G.E.

Rehfeldt : Growth and Cold Hardiness of Intervarietal Hybrids of Douglas-fir

mance of hybrid families for eight variables.

9

A m o d e l of r a n d o m e f f e c t s w a s a s s u m e d

Frost damage

Bud burst

Leaf length

Height deviation ~

PREF

Cd' A

Both nurseries

PREF

Cd' A

0.04 ~ 0 0.12 ~

0 . 4 0 ~* 0 0.03 ~

0 0.29 ~

0 0.03

0.46 ~ 0 0.05 ~

0 . 1 3 *~ 0.21 ~

0.05 ~ 0.44 ~

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0.04 ~ 0.08 ~ .

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0.01 0.11 ~ .

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0.07 ~ 0.22 ~ .

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0.07 ~ 0.22 ~

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0.0 0.03 .

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0 0.03

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0.09 ~ 0.12 ~

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0.06 ~ 0.15 ~ .

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0.28 ~ 0.16 ~ .

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0.25 ~ 0.19 ~

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0.04 ~ .

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0

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0 0

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0.08 ~ 0.75

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0.01 0.04 ~

0 0 .

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0.02 ~ 0 . 0 3 *~

0 .

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0 .

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0.03 ~

0.01

0.05 ~ 0.52

0.05 ~ 0.67

0.01 0.95

0.03 ~ 0.42

0.10 ~ 0.57

0.07 ~ 0.44

Freezing Tests

minimum temperatures

(Levitt 1972). Consistent with

R e s u l t s of a r t i f i c i a l f r e e z i n g t e s t s d e p i c t e x p e c t e d p a t -

variety,

terns for the development of cold hardiness (Table 6).

September tolerated temperatures

The d e v e l o p m e n t o f l o w l e v e l s o f c o l d t o l e r a n c e i s t r i g -

i n j u r e d at - 1 5 ~

g e r e d by f r o s t s a n d d e v e l o p s at a r a t e r e s p o n s i v e t o

w e r e c o n s i s t e n t l y l o w e r at P R E F t h a n at C d ' A , o n l y

r e s u l t s of T i m m i s and W o r r a l l

T a b l e 6. P e r c e n t a g e o f t w i g s d a m a g e d i n f r e e z i n g t r e a t m e n t s

(1975) for the coastal

l i g n i f i e d t w i g s c o l l e c t e d p r i o r to f r o s t in l a t e of - 1 0 ~

but w e r e

Even though minimum temperatures

a c c o r d i n g to n u r s e r i e s

and varieties

24 & 25 S e p t e m b e r

15 & 16 O c t o b e r

4 & 5 November

~C -10 -15

-15

~C -20

-25

-15

~C -22

-30

-20

~C -25

-30

-35

-2

20 & 26 N o v e m b e r

Nurseries PREF Cd'A Varieties

0 0

0 0

87 91

25 74

90 96

98 99

I 1

28 45

93 96

0 0

3 4

21 35

48 70

0 0 0

0 0 0

56 72 100

8 25 75

72 94 98

90 99 100

0 1 8

14 28 79

82 95 100

0 0 4

1 2 24

5 23 52

25 51 89

0 0 0

0 0 0

76 70 98

51 78 89

87 97 100

96 100 100

0 1 4

18 48 89

83 99 98

0 0 4

1 4 16

11 37 75

35 78 96

at PREF

Interior variety Hybrids Coastal variety V a r i e t i e s at C d ' A Interior variety Hybrids Coastal variety

10

T h e o r . Appl. G e n e t . 50 (1977) - 40

c h a r a c t e r i z e d the c o a s t a l v a r i e t y in l a t e S e p t e m b e r ( F i g . 2 ) . Although v a r i a t i o n in h a r d i n e s s c h a r a c t e r i z e d the i n t e r i o r v a r i e t y at e a c h date, v a r i a t i o n f o r

- 35

the c o a s t a l v a r i e t y b e c a m e p r o n o u n c e d as h a r d e n i n g a d v a n c e d . H a r i d n e s s d e v e l o p e d at a f a s t e r r a t e and

- 30

to l o w e r l e v e l s in t r e e s of the i n t e r i o r v a r i e t y than in t h o s e of the c o a s t a l v a r i e t y . Although i n t e r m e d i a t e ,

- 25

h a r d i n e s s of h y b r i d f a m i l i e s was m o r e s i m i l a r to that 0.

of the i n t e r i o r v a r i e t y than the c o a s t a l . In f a c t , the -20

r a t e that h a r d i n e s s d e v e l o p e d in 17 h y b r i d f a m i l i e s e x c e e d e d that of the f a m i l y of i n t e r i o r o r i g i n c h a r a c -15

t e r i z e d by the l o w e s t r a t e . H a r d i n e s s of only f o u r h y b r i d f a m i l i e s d e v e l o p e d at a s l o w e r r a t e than that of COASTALVARIETY~

-10

HYBRIDS[~"~

the c o a s t a l f a m i l y of f a s t e s t r a t e . G e n e t i c r e l a t i o n s h i p s b e t w e e n the h a r d i n e s s of

i 24-26 SEPT.

A 1516OCT.

i 4-5 NOV.

L 20-26 NOV.

DATE

F i g . 2 . Range in a v e r a g e t e m p e r a t u r e s f o r which 50 p e r c e n t of the t w i g s w e r e d a m a g e d at f o u r s a m p l i n g d a t e s f o r t h e c o a s t a l v a r i e t y , i n t e r i o r v a r i e t y , and hybrids

h y b r i d f a m i l i e s at a p a r t i c u l a r date and that of t h e i r p a r e n t a l l i n e s w e r e e x a m i n e d a c c o r d i n g to t h e m o d e l :

Y~cr = a + bX~ + bXcr

where: Y ~ d = t e m p e r a t u r e a s s o c i a t e d with i n j u r y to 50 p e r slight d i f f e r e n c e s in s e e d l i n g h a r d i n e s s during l a t e

cent of the t w i g s f o r the h y b r i d f a m i l y d e v e l o p e d f r o m

S e p t e m b e r co u l d be a s s o c i a t e d with n u r s e r y e n v i r o n -

m a t e r n a l t r e e ~ and p a t e r n a l t r e e d.

m e n t s . As autumn p r o g r e s s e d , h a r d i n e s s d e v e l o p e d at a f a s t e r r a t e f o r t r e e s at t h e c o l d e r P R E F e n v i r o n m e n t than at C d ' A . A t t e m p t s to induce m a x i m u m l e v e l s of h a r d i n e s s evidently failed. Consistent differences associated

X 7 = t e m p e r a t u r e v a l u e f o r the h a l f - s i b f a m i l y r e p r e s e n t i n g m a t e r n a l t r e e ~. Xd - t e m p e r a t u r e v a l u e f o r the h a l f - s i b f a m i l y r e p r e s e n t i n g p a t e r n a l t r e e d. N u r s e r y e f f e c t s h a v e b e e n o m i t t e d f r o m the mode l

with n u r s e r y e n v i r o n m e n t s w e r e found in s a m p l e s c o l -

b e c a u s e e x c e s s i v e e x t r a p o l a t i o n was n e c e s s a r y f or

l e c t e d in l a t e N o v e m b e r . T h e r e f o r e , d e s p i t e t h e c o l d

i n c l u s i o n of t h e i r e f f e c t s . C o m p a r i s o n s of the e f f e c t s

and l en g t h y s t o r a g e , data o b t a i n e d f r o m t w i g s c o l -

of independent v a r i a b l e s on the dependent w e r e m a d e

l e c t e d on 26 N o v e m b e r p r o b a b l y r e f l e c t h a r d i n e s s f o r

a c c o r d i n g to s t a n d a r d i z e d p a r t i a l r e g r e s s i o n c o e f f i -

l a t e N o v e m b e r . R e g a r d l e s s , the c o r r e s p o n d e n c e b e -

cients.

t w e e n o b s e r v e d d a m a g e f o r t h i s date (Table 6) a n d p r e -

As was e x p e c t e d f r o m F i g . 2, h a r d i n e s s of a h y b r i d

v i o u s data (Sakal and ~ / e i s e r 1973) s u g g e s t s that t r e e s

f a m i l y in l a t e S e p t e m b e r was r e l a t e d to that of n e i t h e r

of both v a r i e t i e s w e r e n e a r m a x i m u m l e v e l s of h a r d i -

p a r e n t a l l i n e (Table 7 ) . H o w e v e r , as was i n d i c a t e d by

ness.

s t a n d a r d i z e d p a r t i a l r e g r e s s i o n c o e f f i c i e n t s , the h a r -

F o r e a c h s a m p l i n g date, s e e d l i n g s of t h e c o a s t a l

d i n e s s of h y b r i d s in m i d - O c t o b e r was d e t e r m i n e d by

v a r i e t y s u s t a i n e d m o r e i n j u r y than t h o s e of t he i n t e r -

equal c o n t r i b u t i o n s f r o m t h e m a l e and f e m a l e l i n e s .

i o r . The n u m b e r of i n j u r i e s to h y b r i d s was i n t e r m e -

In N o v e m b e r the effect of t h e m a t e r n a l l i n e was much

di at e b e t w e e n the two (Table 6 ). F o r a s s e s s m e n t of the

m o r e p r o n o u n c e d than that of t h e p a t e r n a l l i n e . R e -

d i f f e r e n t i a l r a t e s that h a r d i n e s s d e v e l o p e d in v a r i o u s

g a r d l e s s , only one m o d el a c c o u n t e d f o r as m u c h as 30

f a m i l i e s , the a v e r a g e t e m p e r a t u r e r e s u l t i n g in i n j u r y

p e r c e n t of the v a r i a t i o n . C o n s i s t e n t with r e s u l t s of

to 50 p e r c e n t of the t w i g s f o r e a c h f a m i l y at e a c h s a m -

n u r s e r y s t u d i e s , d e v e l o p m e n t of h a r d i n e s s in h y b r i d

pling date was e s t i m a t e d b y i n t e r p l a t i o n and, in s o m e

f a m i l i e s a l s o is p r e d i c t e d p o o r l y by that of p a r e n t a l

c a s e s , by e x t r a p o l a t i o n . U n i f o r m l e v e l s of h a r d i n e s s

lines.

G.E.

R e h f e l d t : G r o w t h and C o l d H a r d i n e s s

of I n t e r v a r i e t a l H y b r i d s of D o u g l a s - f i r

T a b l e 7. C o e f f i c i e n t s of d e t e r m i n a t i o n and s t a n d a r d i z e d partial regression coefficients derived from regress i o n s of t h e t e m p e r a t u r e a s s o c i a t e d w i t h 50 p e r c e n t d a m a g e to h y b r i d t w i g s a s p r e d i c t e d f r o m t h a t of t h e i r m a t e r n a l and p a t e r n a l l i n e s

R 2 24 & 25 September 15 & 16 October 4&5 November 20 & 26 November

b'9

b' d

too

..~

g0

/I///111J /

a0

b'9-b' d ~ 8o

0.03

0.16

0.22 ~*

0.23 ~

0 . 3 2 ~* 0.08 ~

ns

-0.03

0.37 ~

0.56 ~

0.24

ns

-0.01

~,

0.09

11

~.~

ns

40

I

II II

I

I I

I

I

I // t

II

/

//o ..~

/

~ f~ ~ ~

30 .Y

~

S i g n i f i c a n c e at t h e 1 p e r c e n t l e v e l of p r o b a b i l i t y ~ S i g n i f i c a n c e at t h e 5 p e r c e n t l e v e l of p r o b a b i l i t y

,.." .."

.~

..,~ - - - - - - Coastal Variety - Hybrid ......... Interior Variety

9 ,.,'"'""

To p r o v i d e a f u r t h e r a s s e s s m e n t

of d i f f e r e n t i a l

0~

0

10

20

a b i l i t i e s of f a m i l i e s to t o l e r a t e f r e e z i n g of v a r i o u s severities,

a linear regression

analysis was made

f o r e a c h f a m i l y a c c o r d i n g to t h e t r a n s f o r m e d

logistic

model :

30

40

50

60

70

80

90

100

SEVERITY OF FREEZING TREATMENT (%)

Fig. 3. Models of freezing damage according to treatment severity for families representing the range in response for the coastal variety (C and U), interior variety (7 and 15), and hybrids (13C and 15E)

1

Yijk = 1 + be-rXk

'

of coastal origin for which which is represented

were

by the linear model

Fig.3 parental \

as few as 12 observations

available. depicts

extreme

varieties

and

models

hybrids.

for families Fig.4

of

illustrates

ijk

where:

100

Y i j k = p r o p o r t i o n of t w i g s i n j u r e d in s a m p l e f r o m f a m i l y j of t r e a t m e n t

severity

i

k.

90

X k = i n d e x of f r e e z i n g s e v e r i t y = p e r c e n t a g e of 80

t w i g s of all f a m i l i e s i n j u r e d by f r e e z i n g t r e a t m e n t k. b=y 0

] - 1 w h e r e YO i s t h e p r e d i c t e d p e r c e n t d a m -

a g e if no f r e e z i n g t r e a t m e n t r = r a t e of i n c r e a s e

i s a p p l i e d (X k = O).

70