I- United States

@

Department of

Agriculture

Southern Forest

Forest Service Research Nate

SO-291

Experiment Station April, 1983

A Study of the Growth, Yield, and Pest Resistance of

Shortleaf X Slash Pine Hybrids

0. 0. Wells and Ft. C. Schmidtling

SUMMARY

At age 10, shortleaf x slash pine hybrids performed relatively poorly when compared with loblolly pine in 10 plantings throughout the southern

pine region. The hybrids excelled only in resistance

to fusiform rust. Over all plantings, loblolly averaged

about 5 feet taller than the hybrids and had almost

twice as much volume. The hybrids’ rust resistance

may make it a valuable source of germ plasm for

breeding programs aimed at producing varieties of

slash pine with a broad genetic base for resistance.

INTRODUCTION

Hybrids involving the southern pines are being

developed in the northeastern part of the Southern

pine region (Little and Trew 1967, 1977, pitch x loblolly), and in central Georgia (LaFarge and Kraus

1960, loblolly x shortleaf). The pitch x loblolly hybrid is to be planted on sites in and near Pennsylvania and West Virginia where climate and soils are

unsuitable for loblolly pine, and the loblolly x shortleaf hybrid is being developed primarily for its rust

resistance in the high rust hazard areas of the

Southeast. A third hybrid, shortleaf x slash pine, has

been suggested as an alternative to loblolly pine on

high rust hazard Piedmont and Upper Coastal Plain

sites in Georgia and Alabama (Wells et al. 1976).

So far, shortleaf x slash pine hybrids have been

adequately tested only for performance in comparison to the parent species.

The present study was designed to test the shortleaf x slash hybrids against loblolly pine, as well as

the parent species, over the long term at several

locations throughout the southern pine region.

The shortleaf female parents of the hybrids are

located in a geographic seed-source plantation on

the Harrison Experimental Forest in south Mississippi. About 10 trees each from Louisiana, Texas,

Arkansas, and Oklahoma seed sources were used

as female parents for a “western hybrid” and about

the same number from Alabama, Georgia, South

Carolina, and Tennessee were used for an “eastern

hybrid”. Eastern and western shortleaf parents were

pollinated in 1964 with a pollen mix from approximately 25 slash pine in a southern Mississippi plantation. The slash pine were of northern Florida origin. Seed from the four eastern sources were mixed

together as were seed from the four western

sources. Hybrid stock was grown at the Harrison

Experimental Forest in southern Mississippi in the

spring of 1966. Seed from natural stands-slash

pine from southern Mississippi and shortleaf from

southeastern Louisiana were included in the test.

Shortleaf pine and loblolly pine from near each

planting site were also included in each planting. All

stocks were grown either in nurseries near the

planting sites or at the U.S. Forest Service Ashe

Nursery near Brooklyn, Mississippi, about 40 miles

north of the Harrison Experimental Forest.

A randomized complete block field design was

used with trees planted at 12 X 12 foot spacing in

49-tree plots with a single isolation row around each

plot. Large plots with buffer rows were used to eliminate between-plot competition, and the trees were

widely spaced to eliminate thinning for many years.

The interior 25 trees were measured periodically.

Each block consisted of the following sources of

stock: (A) shortleaf x slash, western source; (B)

Southern Foreat Experiment Station/T-10210 U.S. Postal Servlcee Bldg., 701 Loyola Avenue, New Orleans, La. 70113

forest Service, U.S. Department ot Agriculture.

Sewing Alabama, Arkansas, Louisiana, Mlaairslppl, E. Oklahoma, Tennessee, E. Texas, Puerto Rico, U.S. Virgin Islands
O K

Figure l.-Planthg locations. The Oklahoma and Arkansas 2 (Yell County) plantings were established In

1966-6; the others in 7968-69.

shortleaf x slash, eastern source; (C) shortleaf control, St. Helena Parish, Louisiana; (D) shortleaf control, local source; (E) slash control, southern Mississippi; and (F) loblolly control, local source. These

6 sources were replicated in 5 blocks at each of 10

planting locations.

Ten plantings were established in the 1968-67

planting season, one near Oklahoma State University and nine on National Forests. Planting survival,

generally low, ranged from complete failure in Polk

County, Tennessee, and McCreary County, Kentucky, to an average survival of 77 percent in McCurtain County, Oklahoma. Unusually low temperatures immediately after establishment at the northern locations and a generally dry spring were the

major causes of poor survival in 1967. Because of

mild temperature, neither stocks produced in the

Harrison Experimental Forest nursery nor the local

checks at two more northerly nurseries hardened

for winter sufficiently to survive planting.

Because of the poor survival, eight plantings of

the same seedlots in the same design were reestablished in the 1968-69 season. All seedlings including local stocks were grown in the Ashe Nursery.

Planting survival was good and with the two plantings from the 1966-67 season that were retainedin McCurtain County, Oklahoma and Yell County,

Arkansas-the study was established as designed.

(fig. 1).

Data were collected on survival, height, diameter,

and fusiform rust incidence after 3, 5, and 10 years

in the 1968-69 plantings and after 3,6, and 12 years

in the 1966-67 plantings. Analysis of variance and

Duncan’s Multiple-Range Test was used to test

for differences among sources.

RESULTS

Planting Survival.-Planting survival was above

90 percent for four of the eight plantings established

in the winter of 1968-69 and above 80 percent in all

but one other. Only the northern Mississippi planting had fairly low survival-81 percent. Relatively

few genetic differences in survival were expressed

under these non-stressful conditions. In lower-sur0. 0. Wells and FL C. Schmidtling are Principal Plant Geneticistics, USDA Forest Service, Southern Forest Experiment Station,

Forestry Sciences Laboratory, Gulfport, Mississippi.

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Table l.-Survivai at 10 years of hybrids a& check species in six plantings ecpt of the Mississippi River

and af 12 years in hvo plantings wesl of Iha River

Hybrid or

check species

Local loblolly

South MS Slash

Western hybrid

Eastern hybrid

SE LA shortleaf

Local shortleaf

Eastern planting location Western planting location

KY TN N MS N AL N GA SAL Avg O K AR 4

--------------------------------------porcent--------------------------------------

9 1 8 8 9 0 9 4 7 7 9 4 89d’ 8 8 9 9 94’

4 1 8 8 6 9 7 4 6 2 6 6 67b 6 8 3 0 4 9

6 4 8 1 5 6 7 1 7 4 8 3 88b 5 8 4 2 50

6 6 5 6 3 3 6 1 6 1 5 8 56a 4 2 3 0 3 7

6 4 8 7 5 8 9 3 9 3 9 6 81~ 6 0 5 0 5 5

9 0 8 4 6 7 6 9 8 5 9 7 85cd 6 8 6 2 8 5

‘Means opposite the same letter are not significantly different at the 0.05 percent level.

Fitatistical analysis not done because local loblolly and shortleaf were grown in different nurseries.

Table P.-Average volume per acre al 70 years-hybrids and check species in six plantings

east of the Mississippi River

- - -

Hybrid or Eastern planting location

check species -zY T N N MS N AL N GA S AL Am

Local loblolly

South MS Slash

Western hybrid

Eastern hybrid

SE LA shortleaf

Local shortleaf

.---------------------------fr/acre.------------------------------:

339 279 935 333 778 1302 6818’

5 7 115 452 208 426 676 322~

107 7 9 324 176 615 1035 389d

7 7 7 8 191 149 443 507 241a

6 7 51 205 137 547 948 325~

107 9 3 287 114 345 855 297b

‘Means opposite the same letter are not significantly different at the 0.05 percent level.

viva1 areas, the hybrid made with eastern shortleaf

averaged only 64 percent planting survival while the

western hybrid averaged 81 percent.

Interpretation of survival results in the two 1966-

67 plantings was complicated by variations in stock

sources. The Yell County, Arkansas planting had 98

percent survival of the trees grown at the U.S. Forest Service Ashe Nursery, but only 47 percent of the

stock from the Harrison Experimental Forest survived.

Post-Establishment Survival.-Between establishment and measurment at 10 or 12 years, the plantings in northern Arkansas and southern Mississippi

suffered heavy nonrandom mortality from weed

competition and fire respectively, and were abandoned. In the other plantings, the hybrids generally

suffered more mortality than local shortleaf or loblolly (table i), particularly in the Oklahoma and Yell

County, Arkansas plantings. Many of the hybrids

that did not survive were dwarfs. Dwarfing has been

previously reported in hybrids between slash and

shortleaf pines (Schmitt 1969). The planting in northern Alabama showed height distribution bf the eastern hybrids at 6 years (fig. 2A)sKewed more towards

the shorter height classes than in the non-hybrid

stocks. At 10 years (fig. 28) many of these short

trees had died. As seedlings destined to be dwarfs

are hard to recognize during nursery operations,

culling is impractical. If some mortality from this

cause is expected, slightly increased planting density could easily make up the difference.

Slash pine, in a response to cold climate, also

suffered greater than average mortality between

establishment and age 10 in the northern and midlatitude plantings. Mortality was most pronounced in

the most northern plantings (Kentucky, Tennessee,

North Georgia) and trees of any size, large or small,

were affected at random.

The local loblolly and shortleaf generally had

higher survival than the hybrids or slash pine, both

at establishment and after 10 or 12 years in the field.

Height.-Local loblolly was the fastest-growing

stock in the test. It ranked first in 10th or 12th year

dominant-codominant height in seven of eight plantings (fig. 3). Only the Oklahoma planting of slash

pine ranked higher.

The shortleaf stocks generally grew slowest in

all plantings with the two hybrids stocks and slash

pine intermediate, but in Oklahoma local shortleaf

grew faster than the hybrids.

3
A. B-YEAR HEIGHTS ’ 8. IO-YEAR HEIGHTS *

lYORTM 4LA64YA

soInn ALAIAYA

NORTH OCOLIOIA

SPLCILS OR nr6nlD

Figure P.-Frequency distribution of helghta rt 6 (Co/. A) and

10 (Co/. B) years in CIeburne Ccunty, (northern)

Alabama planting.

The hybrids made with western shortleaf averaged about 2 feet taller than those of eastern shortleaf in the eastern plantings, but the hybrid groups

were about the same height in the western planting.

Volume.-A conic formula was used to compute

total bole volume per plot.

volume= 1 w dzh

-umzP

where:

Rust Resistance.-Only three plantings had

enough rust infection to demonstrate differences in

resistance among hybrids and check species; only

one planting-Jones County, Georgia-had over 65

percent stem plus branch infection on the susceptible slash and iobloiiy pine (table 3).

n = number of trees surviving on each plot in two of the three piantings-Covington, Alad = average plot dbh in inches bama and Jones County, Georgia-the slash and

h=average plot height in feet lobioliy pines were most heavily infected, the shortPlot volumes were then converted to a per acre ba- leaf had negligible infection, and the two hybrids

sis. Analysis was confined to the six eastern piant- were lightly infected. in the Cieburne County, Alaings where nursery source was held constant. bama planting, however, the hybrids had almost as

The formula combines growth rate and survival. much infection as slash and lobioiiy pines. This is

Since local iobioiiy performed well in both these re- most unusual because in other trials (Wells et al.

spects, its advantage over the hybrids and other 1978) the shortleaf x slash pine hvh*?s have reacted

check species was even greater than in either of the as they did in the Covington County, Alabama and

component traits taken singly. Local loblolly, first Jones County, Georgia plantings in the present

Figure 3.-Height over 8ge In six 1968-69 plantings and two.

7966-67 plantings (Oklahoma and Arkansas 2).

in volume in each planting, showed, over all plantings, about twice as much volume as the hybrids

and other check species (table 2).

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Table 3.-Trees with stem or branch galls in three pla$ings

Hybrids or Planting location

check species Covington, AL Jones County, GA Cleburne County, AL Avg

---------------------------------percent-----------------------------

Local loblolly 23.8 69.4 16.5 37.2

South MS Slash 5.3 63.9 39.7 36.3

Western hybrid 0.8 9.6 26.5 12.4

Eastern hybrid 0.9 11.2 18.7 10.3

SE LA shortleat 0 4.3 0 1.4

Local shortleaf 0 1.0 0.8 0.6

study-their infection rate has been much closer to

the nearly immune shortleaf pine than to the susceptible slash and loblolly pine.

In practical terms, the hybrid can be considered

very resistant. Combining stem plus branch infections was necessary in the present study to get infection rates high enough for a definitive test. Not

enough stem infection occurred on the hybrids to

demonstrate adequately differences in resistance

among the hybrids and checks.

DISCUSSIONS AND CONCLUSIONS

The hybrids have not performed well in this study.

Their survival, both immediately after planting and

in the long run, has not been as good as the check

species and their growth rate is unimpressive, particularly when compared with loblolly. Loblolly is

most often the species recommended for planting

above the flatwoods on coastal plain and Piedmont

sites in the Southeast.

The hybrids have good rust resistance, but re

sistant loblolly is also available, either from natural

populations or, increasingly now, from orchards selected for other traits as well. The shortleaf x loblolly

hybrid is another alternative source of rust resistance (La Farge and Kraus, 1980) for the southeastern United States.

Perhaps the best use of the shortleaf x slash hybrid would be as a source of variation in a breeding

program. It’s rust resistance derives from a source

-shortleaf pine-that is not ordinarily present in

natural evolving populations of slash pine. Penetic

diversity is necessary in advanced generations of

breeding programs and incorporating highly diverse germ plasm, such as this, into a slash pine

breeding program might be worthwhile. Development of rust resistant slash pine is a high priority

need of the Florida Cooperative (Goodard et al.

1981) and presumably other planters of slash pine,

so an improved variety is readily marketable.

LITERATURE CITED

Goddard, R. E.; A. E. Squillace; 0.0. Wells. Genetic

improvement of slash pine. In: Proceedings, Slash

pine symposium; 1981 June 9-l 1; Gainesville, FL.

Gainesville, FL.: University of Florida Press; (In

Press).

LaFarge, T.; Kraus, J. F. A progeny test of (shortleaf x loblolly) x loblolly hybrids to produce rapidgrowing hybrids resistant to fusiform rust. Silvae

Genet. 29(5-8); 197-200; 1980.

Little, S.; Trew, I. F. Breeding and testing pitch x loblolly pine hybrids for the Northeast. In: Proceedings, 23rd Northeastern forest tree improvement

conference; 1975 August 4-7, New Brunswick,

N.J.; Upper Darby, PA: Northeastern Forest ,Experiment Station;; 1978: 71-85.

Little, S.; Trew, I. F. Progress report on testing pitch

x loblolly pine hybrids and-on providing hybrid

seed for mass planting. In: Proceedings, 24th

Northeasten forest tree improvement conference:

1978 July 28-29; College Park, MD.: Center for

Environmental and Estuarine Studies; 1977: 14-

28.

Schmitt, D. Nanism in slash x shortleaf pine hybrids.

For. Sci. 15(2): 174-175; 1989.

Wells, 0. 0.; Barnett, P. E.; Derr, H. J.; Funk, D. T.;

LaFarge, Timothy; Lawson, E. R.; Little, Silas.

Shortleaf x slash pine hybrids outperform parents

in parts of the southeast. South. J. Appl. For. l(1):

28-32; 1978.

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