Genetic Gains Through Testing and Crossing

Longleaf Pine Plus Trees

CALVIN E BEY AND E: BAYNE SNYDER

SUMMARY

A progeny test of 226 superior tree selections

from nine geographic sources across the South

confirmed earlier results that showed the Gulf

Coast source superior in survival and growth.

Family variation within a region was large and

provided additional genetic gain. Control-pollinated tests of elite x elite trees yielded even

more gains. Progeny of the elite x elite crosses

had higher survival, less brown-spot infection,

and greater wood volume than progeny from

crosses involving only one or no elite parent.

Additional keywords: Pinus palustris, geographic variation, progeny test, survival, growth,

brown-spot needle blight.

IMPROVING BREEDING PROCEDURES

Good form, natural pruning, and high quality

wood favor longleaf pine (Pinus palustris Mill.)

for use as poles and lumber in the South. Yet

because of low planting survival, susceptibility

to brown-spot needle blight [Scirrhia acicola

(Dearn.) Siggersl, and slow early growth, it has

not been widely planted. Tree improvement offers an opportunity for overcoming these negative traits. In studies reported here, objectives

were to show geographic seed source trends,

family variation for each of nine geographic

areas, and gains realized at ages 12 and 13

through control-pollination among elite parents.

METHODS AND MATERIALS

We established three randomized complete

block studies. Test A was a progeny test of 226

superior tree selections divided among nine

geographic sources across the South (Derr

1971). Included as a control were the wind-pollinated progeny of an elite parent, “Abe” (Derr

1963). In 1969, l-year-old potted trees were

planted in plowed furrows on a fertile, welldrained, sandy loam soil near Alexandria, Louisiana. Four replications of 10 seedlings per

row-plot were planted at 6 ft x 8 ft spacing. Data

collected or calculated were:

Age 2 - Height and percentage of needle

tissue killed by brown spot

Age 5 - Height

Age 6 - Height; diameter; percentage of surviving trees, trees with fusiform rust,

trees with crooks, or trees with forks.

Percentage figures were transformed by an arc

sine procedure for analyses of variance. For 8-

year growth, average volume per tree and volume per plot were computed.

In test B, 16 random parents were wind-pollinated and control-pollinated by Abe. The Abe

x wind family was included as a control. Potted

seedlings from the 37 families were transplanted to plowed furrows in the spring of 1965.

The study is located at Alexandria, Louisiana,

and consists of three replications of 20-tree

row-plots. Data were collected at age 2 from all

families for height, survival, and percentage of

brown-spot infection. At age 12, we remeasured

height, diameter, and survival for’the two random x Abe families that were tallest at age 2,

Abe x wind, and random tree 3 x wind (an average random control). The two tallest random

Southern Forest Experiment Station/T-l0210 U.S. Postal Services Bldg., 701 Loyola Avenue, New Orleans, La. 70113

Forest Service, U.S. Department of Agriculture.

Serving Alabama, Arkansas, Louisiana, Mississippi. Eastern Oklahoma. Tennessee, Eastern Texas.
parents probably have above average genotypes.. Mean volume per tree and volume per

plot were computed.

In test C, we compared families derived by

crossing Abe with two elite trees (including reciprocals), Abe x wind, and four random trees x

wind. For comparison we grouped crosses with

their reciprocal crosses and also the four random x wind crosses. These and other intermediate crosses were included in earlier analyses

(Derr and Melder 1970). The test was established in 1964 at Alexandria, Louisiana, with

four replications of 25tree plots. At age 3, data

were collected from all families for percentage

of brown-spot infection, survival, and height.

Height, diameter, and survival data were collected at age 13 from the elite x elite crosses,

Abe x wind, and a representative random control (4-1 x wind). Average volume per tree and

volume per plot were computed.

RESULTS AND DISCUSSION

Test A-Geographic seed source effects

After 8 years, progeny from plus trees of the

south Alabama source had the largest volume

per tree and volume per plot among all sources

(table 1). The source means were significantly

different. This confirmed results from the

Southwide Pine Seed Source Study, which used

randomly selected trees and showed, that the

Gulf Coast source excelled over most of the

commercial range of longleaf (Wells and Wakeley 1970). For current reforestation and tree

improvement programs in Louisiana, the Gulf

Coast source should be emphasized. In this experiment the south Alabama source had 58

percent survival (vs. 29 percent for the Louisiana source) and had 157 percent more volume

per plot than did the Louisiana source. On the

basis of volume per plot, we should not use

Texas, North Carolina, or Louisiana seed in

Louisiana unless we can find better clones from

these sources. The downward trend of the relative height growth of northern Alabama trees

between 5 and 8 years also cautions against

use of this source in Louisiana.

The South Carolina source had unexpectedly

good growth. Its origin is much farther north

than the three other best performing sources

and is over 350 miles northeast from the recommended central Gulf Coast seed collection

area. Although we would be cautious in recommending trees from the South Carolina source

for planting in Louisiana, the growth potential

looks good. The South Carolina source deserves additional testing, particularly in areas

across the northern part of the longleaf range.

Variation in brown-spot infection contributed

most to a-year volume per plot variation among

seed sources. However, additional variation was

accounted for by including 2-year height

growth. The prediction that provided best fit for

a-year volume was the e-year percentage of foliage free of infection x the P-year height growth

(R* = 0.91). The high correlation is further evidence of the efficiency of early testing and selection before seed orchard establishment.

Although e-year height growth .differences

were significant, the range was narrow (0.36 to

0.49 ft) and not well correlated with later height

data. By age 5, family height growth differences

were well expressed and correlated with a-year

Table 1 .-Progeny performance by source of seed in test of 226 National Forest clones (Test A)

No of Wear

s-year

Source Fam. Brown P-year g-year Survival Rust Height Diameter Avg. Avg. Range

Swt Height Height volume/ volume/ volume/

tree plot plot

Percent Feet Feet Percent Percent Feet Inches Feet3 Feet3

South Alabama 2 2 1 8 0.42 6.67 5 8 9 19.9 2.86 0.415 2.52 .71 - 4.39

South Carolina 3 7 2 1 0.44 6.31 5 8 5 19.2 2.87 0.402 2.29 .58 - 4.48

Mississippi 2 2 2 5 0.45 6.01 5 6 8 19.0 2.71 0.371 2.11 .65 - 3.84

Florida 2 5 2 0 0.46 6.68 4 9 8 20.0 2.89 0.415 2.05 .74 - 4.11

North Alabama 3 3 2 1 0.41 5.93 5 7 9 18.2 2.74 0.349 2.02 .73 - 3.66

Texas 4 2 3 2 0.49 5.15 3 9 5 18.8 2.75 0.374 1.51 .09 - 3.45

North Carolina 1 3 3 3 0.38 4.07 3 2 8 17.4 2.70 0.334 1.14 .52 - 2.00

Louisiana 3 2 3 8 0.40 3.73 2 9 8 18.0 2.60 0.320 0.98 .18 - 2.09

Mean 2 6 0.43 5.60 4 7 6 18.9 2.77 0.376 1.83

Significance I S S S S N S S S S S

‘S - significant at 0.01 level; NS = not significant

Calvin F. Bey and E. Bayne Snyder are Principal Plant Geneticists, Southern Forest Experiment Station, Forest ServiceUSDA, Gulfport, Mississippi.

2
heights (r = 0.37). Height trends from age 5 to

age 8 must be evaluated in conjunction with

survival differences. At first, the fastest growing

sources tend to survive best. As crowding begins, trees in the slower growing and less dense

sources begin to catch up because they have

more growing room. In this test, crowding was

occurring so the study was ended.

Crook and forking is not usually a problem in

longleaf pine. Mean frequency of trees crooked

or forked ranged from 0 to 4 percent. Because

the frequency of crook within and among

sources was so low, no statistical analyses were

made.

Variation and selection of families

within sources

Because growth of the best families within

sources is often of more interest to breeders

than that of source averages for all families,

we looked at the heights for the top 12 percent

of the families in each source. Surprisingly,

mean heights for the top 12 percent of the families from the south Alabama, South Carolina,

Mississippi, Florida, and Texas sources all converged at 21.1 Z+Z 0.1 ft. The trees are closely

spaced (6 x 6 ft), and height convergence is

probably caused by crowding. Under these

spacing conditions, geographic source height

differences are not easily differentiated by ‘using only the tallest families.

Volume of wood per unit area is probably the

most useful family selection trait. Among families with the highest wood volume per unit area,

those with the highest fusiform rust or crook

ratings should be avoided. In this progeny test,

which is being converted to a breeding arboretum, the 70 best families out of 226 were saved.

At age 8, the 70 selected families averaged 2.92

ft3 in volume per plot, or 60 percent more than

the 1.83 ftsaverage for ail families. Within each

lo-tree plot of each selected family, only the

best tree was saved. This within-family selection

will provide additional gains.

Although volume selection at age 8 may seem

early enough in the life of the plantation for

some, we believe that even earlier selection has

some merit. We were reasonably successful in

estimating a-year volume from 2-year height

and 2-year brown-spot infection. Correlation between observed and estimated values was r =

0.69. This is considered good, since we are

going from a few inches tall at age 2 to 20-30

feet at age 8. Certainly by age 3 or 4, when the

trees are out of the grass stage, the correlation

would be even higher. Initial screening or selection at this age seems appropriate for making

initial parent tree selections or for roguing a

seedling seed orchard.

The 70 families were selected without regard

for geographic seed source effects. The number of families selected per geographic source

therefore depended upon average source performance and total number of families per

source in the test. The number and percentage

of families selected from each source were:

SC-l 7 (40 percent), MS-1 5 (41 percent), S. AL12 (54 percent), N. AL-10 (30 percent), FL-8

(32 percent), TX-7 (17 percent), LA-l (3 percent), NC-O (0 percent)!

This progeny test has provided satisfactory

brown-spot evaluation for all families. In using

these data from a single planting we assume

little genotype x environment interaction for

brown spot. The test will also serve for roguing

on the basis of growth in the nearby Kisatchie

clonal seed orchard. However, only clones from

the Kisatchie Forest and Texas are included in

the orchard, and their overall performance in

the progeny test was poor. For greater genetic

gain for this region, faster growing eastern

clones should be included in the Kisatchie seed

orchard.

The test information is also satisfactory for

moderately roguing clones to be planted in

other areas where brown spot is serious. However, for seed’orchards in areas that are unlike

the test region, especially North Carolina and

north Alabama, this progeny test should not be

used. Trees selected for adaptation to one area

are not necessarily those adapted to another

(Snyder and Bey 1978). In the future, orchards

should include selections from the most promising geographic sources in addition to the local

source. Orchards should be rogued on the basis

of progeny tests in the area where the seed is to

be used. Progeny testing for brown-spot resistance and early growth is necessary for rapid

advancement in tree improvement programs.

Tests B and C-Crossing among the elite

Material similar to the elite clones in Test A

were intercrossed (table 3). Results at age 12

to 13 indicate that much additional gain can be

made by intercrossing elite parents. Progeny of

crosses involving elite parents generally survived much better than progeny from crosses

involving only one or no elite parent. The poor

survival of wind-pollinated (random) material

is perhaps the most surprising and important

result of all. Only progeny from the elite x elite

1 Data similar to those for south Alabama for all 226 families

for brown spot, fusiform rust, survival, B-year height. and

8-year volume (table 2) are available from the’authors.

3
Table P.-The ranks c :,amilies from the Conecuh N.F., Alabama (Test A) ranked by volume per

plot

Forest and clone ID P-year 5-year a-year 8-year 8-year 8-year

brown spot height rust survival vol/tree vol/plot

Percent Feet

12ALCON 88 2 3 9 9.04

20ALCON 100 31 8 8.92

22 AL CON 185 41 1 1 8.90

2ALCON 18 1 9 1 8 7.17

4ALCON 36 14 !2 7.74

8ALCON 4 7 8 1 4 7.32

17ALCbN 92 8 14 7.31

15 AL CON 7 5 3 2 2 7.24

1OALCON 81 1 0 1 0 7.31

11 ALCON 8 5 12 15 7.78

3 AL CON 35 13 2 0 8.38

5 AL CON 40 16 2 0 7.46

19 AL CON 98 30 10 6.42

21 AL CON 138 1 8 1 9 8.81

18 AL CON 96 2 8 2 0 6.75

16 AL CON 80 4 16 6.25

14 AL CON 7 2 2 5 2 6 5.72

13ALCON 71 2 4 15 4.93

7ALCON 50 9 21 5.31

9 AL CON 58 21 2 6 4.41

8 AL CON 5 5 2 0 21 4.63

1ALCON 4 2 39 2.88

Means for:

Conecuh N.F.,

Ala. 1 8 6.67

Region 2 6 5.60

Percent

3

3

9

2 7

3

15

3

1 8

1 1

4

18

6

1 5

15

9

10

4

3

15

0

0

1 3

9 5 8 0.415 2.518

6 47 0.376 1.830

30

7 2

8 0

80

71

7 0

6 5

63

65

5 5

60

6 5

80

5 2

5 2

62

4 7

5 2

50

40

38

1 5

Feet3 Feet 3

0.551 4.391

0.504 3.821

0.485 3.802

0.542 3.511

0.455 3.184

0.439 2.938

0.421 2.890

0.449 2.772

0.414 2.713

0.490 2.623

0.447 2.597

0.395 2.566

0.381 2.278

0.410 2.222

0.391 2.218

0.347 2.189

0.390 2.019

0.305 1.775

0.331 1.690

0.351 1.450

0.246 1.027

0.386 0.714

Control (Abe) 2 2 8.40 0 5 6 0.483 2.510

crosses had acceptable survival (35 to 86 percent). Survival in the random x wind and even

Abe x wind progeny was very poor (0 to 18

percent). It is hardly surprising that planting runof-the-mill longleaf seedlings has been discouraging to many foresters.

Families derived from crossing elite x elite

parents also were taller, had better brown-spot

resistance, greater volume per tree, and five or

more times greater volume per plot than random material. In Test C, progeny in the best

cross (i-2 x Abe) averaged about 3 feet per year

in height growth and one-half inch per year in

diameter growth. The general superiority in

height growth at age 12 to 13 for crosses between elite parents can be attributed in part to

their coming out of the grass stage earlier and

in part to their brown-spot resistance. Many

trees from the elite parents were out of the

grass stage by age 3. In most cases, brown-spot

incidence in progeny of elite parents was onethird to one-half that of random material.

The high correlation between early brown

spot readings and 8-year volume in this study

and evidence from other studies suggest that

for first generation orchards, the use of shortterm, open-pollinated progeny tests that are

completed before grafting might be more efficient than the traditional pine seed orchard approach (Schoenike and Williams 1975). Rather

than using rigorous individual tree selection

standards, we recommend that a larger number

of less intensively selected parent trees be

tested. As shown in this study, even with intensive phenotypic selection, many trees with

low breeding value are included. Rather than

grafting parents into an orchard at time of

selection, we recommend waiting until the

breeding value is estimated from open-pollinated progeny tests. Then the elite can be

grafted into an orchard, or the progeny test itself can be heavily rogued to make a seedling

seed orchard.

If the latter approach is adopted, trees can be

closely spaced to accommodate early roguing

(Snyder and Derr 1972, Rockwood and Kok

1977). Whatever approach is used, tree improvement specialists need to recognize and

use geographic variation to obtain maximum

improvement for the species.

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Table 3.-Open- and controlled-pollination result. for random and elite parents in progeny tests B and C

Type of Pollination

Brown

spot Survival H t Survival H t D.B.H. Vol/tree Vol/plot

percent percent inches percent feet inches feet3 feet3

Test 6 Age 2 -Age 1 2

Random (1 QY) x

Elite Abe 4 1 9 8 2 4 4 7 2 9 8.0 2.19 20.8

Random (QA) x

Elite Abe 3 7 9 5 2 3 3 5 3 2 6.0 2.39 16.7

Abe x Wind 6 2 9 3 1 1 1 2 2 6 5.5 1.60 3.8

Random (1Y) x

Wind (control) 7 5 6 7 5 0 0 0 0 0

18 random trees

x Abe 5 2 9 2 1 6 - - -

18 random trees

x wind 7 4 9 0 5 -

Significance’ S N S S S N A N A N A N A

Test C Age 3 - -Age 1 3

Elite 1-2x Elite Abe lQ1 9 9 28* 8 6 3 8 6.2 3.30 71.0

Elite 1-3 x Elite Abe 2 2 100 2 5 6 5 3 4 5.7 2.36 50.0

Elite Abe x Wind 4 2 9 4 2 1 5 8 3 5 5.6 2.44 35.6

Random 4-1 x wind 6 5 9 9 6 1 8 3 1 5.2 2.18 10.0

4 random trees

x wind 6 5 9 6 8

Significance’ S N S S S S N S s . S

‘S - signficantat .05 level; NS - not-significant: NA - not applicable because there were no surviving controls

*Data from Derr and Melder 1970.

LITERATURE CITED

Den, H. J.

1963. Brown-spot resistance among F1 progeny of a single resistant longleaf parent. In

For. Genet. Workshop Proc., p. 16-l 7.

Derr, H. J.

1971. Brown-spot resistance among progenies of longleaf plus trees. In 1 lth South.

For. Tree Improv. Conf. Proc., p. 45-51.

Derr, H. J., and T. W. Melder.

1970. Brown-spot resistance in longleaf pine.

For. Sci. 16: 204-209.

Rockwood, 0. L., and H. R. Kok.

1977. Development and potential of a longleaf pine seedling seed orchard. In 14th

South. For. Tree Improv. Conf. Proc., p. 78-

86.

Schoenike, R. E., and J. G. Williams.

1975. Ten-year results of an open-pollinated

progeny test of longleaf pine in South Carolina. In 13th South. For. Tree Improv. Conf.

Proc., p. 97-104.

Snyder, E. B., and C. F. Bey.

1978. Progeny testing longleaf pine at two locations. U.S. Dep. Agric. For. Serv. Res.

Note SO-240, 4 p South. For. Exp. Stn.,

New Orleans, La.

Snyder, E. B., and H. J. Derr.

1972. Breeding longleaf pines for resistance

to brown-spot needle blight. Phytopathology 62: 325-329.

Wells, 0. O., and P C. Wakeley.

1970. Variation in longleaf pine from several

geographic sources. For. Sci. 16: 28-42.

* U.S. GOVERNMENT PRINTING OFFICE: 1978-773222

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