yl Georgia Forestry Commission QgS'M Research REPORT Jo. 5 April, 1989 GAIN AND VARIATION After Two Generations Of Selection In Slash Pine In Georgia By Earl R. Sluder eceived 1 1989 DOCUMENTS UGA LIBRARIES Author s* Earl R. Sluder is a plant geneticists with the Regeneration and Breeding of Loblolly Pine in the Southeast Project of the Southeastern Forest Experi- ment Station, USDA Forest Service, at Macon, Georgia. He received his B.S., M.S. and Ph. D. degrees from North Carolina State University at Raleigh. GAIN AND VARIATION After Two Generations Of Selection In Slash Pine In Georgia by Earl R. Sluder ABSTRACT Wind-pollinated slash pine progenies from (1 ) eight first-generation seed orchard clones, (2) bulked seed from their eight progenies in a 15year-old seedling seed orchard, and (3) 1 5 individual second-generation selections from the progenies in the seedling seed orchard were tested on an Upper Coastal Plain and a flatwoods site in Georgia. Contrasts between progeny groups and checklots at age 5 years show that each selection stage beyond the unrogued cloanal seed orchard produced gain in resistance to fusiform rust. Variation within groups of first- and second- generation progenies remained high enough to afford further progress from selection, particularly in fusiform-rust resistance. Genetic improvements in agricultural crops and domestic animals are greatly increasing profitability in agriculture and animal husbandry. The southern pines are being planted and grown as a crop, which presents both the opportunity and the need to apply genetic principles to increase prof- itability in forestry. In the early 1950's Georgia Forestry Commission foresters located several hundred well-formed, fastgrowing disease-free slash pines (Pinus elliottii Engelm. var. elliottii) as candidates for a tree improvement program. After further screening, 1 49 of these selected trees were propagated by grafting and used to establish two clonal seed orchards to supply seed needed for planting in Georgia. Trees grown from these seeds are expected to be better in growth rate and other traits than trees from seeds collected in natural stands. But the only way to find out if they are better, and how much better, is to compare per- formance of their progeny with that of natural-stand check lots in properly designed studies. Questions about the potential for gain in succeeding generations of selec- tion and breeding are: (1 ) How much genetic variation in economic traits is harbored in the selected genotypes? (2) How much gain can be made each generation? (3) Over how many generations of selection and breeding can suc- cessive gains be made? As soon as ramets of the seed orchard clones began flowering, the Georgia Forestry Commission, in cooperation with the Southeastern Forest Experimetn Station, USDA Forest Service, began controlled pollinations to progeny test the clones. The first progeny tests, planted in 1961, included a plantation designed for conversion to a seedling-origin seed orchard. When the conversion was completed and the remaining seedling-origin seed orchard trees were flowering, a study was designed to quantify gains made in this second-generation orchard, to compare them with gains made in the first generation clonal orchard, and to compare performance of progenies from both orchards with that of natural-stand check lots. Materials and Methods The progenies included in the second-generation seedling seed orchard were from controlled pollinations of 1 7 of the clones in the first-generation clonal orchard. A mixture of pollen from 30 other clones in the orchard was used on these 1 7. The 1 7 "polymix" progenies produced were planted in a replicated design at the Georgia Forestry Commission's Arrowhead Seed Orchard in Pulaski County. Some 2,635 seedlings were planted. Roguing in 1967, 1969, 1971, and 1974 reduced the number to 141 trees, 5.35 percent of the original number. Trees removed were those (1) infected by the fusiform-rust fungus (Cronartium quercuum (Berk.) Miyabe ex Shirai f. sp. fusiforme), (2) with obviously slow growth, or (3) with poor stem or branch characteristics. In the 1 974 roguing, spacing and flower production also were considered. One progeny that consistently grew slowly and had high fusiform-rust susceptibility was eliminated in 1 974. All cones were collected from the remaining seedling seed orchard trees in 1975 (about 4,000 cones) and 1 976 (about 1 7,000 cones). Each year, the seeds were kept separate by individual tree. A bulk lot representing the rogued seedling seed orchard was made in each of the two years by mixing seed from each tree in proportion to that tree's contribution to total orchard yield. These two bulk lots were overall orchard check lots. In addition, eight family bulk lots were made from the 1 976 collection. The three kinds of seed lots available from the seedling seed orchard, therefore, were two overall bulk lots, eight family bulk lots, and individual-tree lots, all from wind-polli- nated seeds. The maternal parents of the eight seedling orchard families from which the bulk seed lots were made are still in the rogued first-generation clonal orchard. Windpollinated seeds were collected from these eight clones for use in the study. Both seed orchards are surrounded by a large area of loblolly pine-hardwood forest and farm land, so outside slash pine pollen is at a very low level. Two other check lots were obtained from the Georgia Crop Improvement Association. One was commercial seed from Telfair, Treutlen and Emanuel Counties, and the other a bulk lot from the unrogued first-generation clonal orchard. Both were collected in 1 965. Four kinds of seed lots were included in the study: (1) wind-pollinated seeds from eight of the clones remaining in the rogued first-generation orchard; (2) family-bulk lots from second-generation polymix progenies of the eight clones in (1), which were in a rogued seedling seed orchard; (3) individual-tree lots from 1 5 second-generation trees selected from 6 of the progenies in (2); and (4) four check lots -- two bulk lots from the seedling seed orchard, one bulk lot from the unrogued clonal orchard, and a commercial collection. The total number of seedlots was 35 (Appendix table 1 ). Seedlings for the study were grown in 1 978 by the Georgia Forestry Commission in the Morgan Nursery near Byron, GA., and planted as 1-0 stock in the spring of 1 979 on two test sites in Georgia. One was a flatwoods site in Ware County and the other an Upper Coastal Plain site in Houston County. At both locations each seed lot was replicated five times in 1 6-tree plots in a randomized com- plete block design. Spacing was 2.5m x 2. 5m (8.2' x 8.2) in Houston County and 2.5m in bedded rows approximately 3.7m (1 2') apart in Ware County. At ages 2, 3, and 5 years, survival, height, and fusiformrust infection were measured or assessed at both test sites. Only the fifth-year results are reported here, but the fifth-year rust data reflect all mortality from rust through age 5. Rustinfection was expressed as thenumberof cankers per seedling and as the percentage of seedlings free of rust at age 5. Prior to analysis of variance, percentages were transformed to arcsins of their square roots. Means were separated with Duncan's multiple range test (Duncan 1955). Data were analyzed for each of the two planting sites and for the two sites combined. The various check lots and family and progeny groups in this study represent stages of selection ranging from unselected natural stands to progenies from secondgeneration selections. Six contrasts between means of these groups were contstructed and tested for significance. Also, the relative variation remaining among families within groups (1), (2), and (3) above was determined. RESULTS AND DISCUSSION Trait means for the groups representing the various stages of selection, along with six contrasts and their significance tests, are shown in Table 1. The numbers assigned to the seedlots in Table 1 represent the various stages of selection and breeding, and the contrasts were designed to show gains made in individual stages. Only one contrast was significant on the flatwoods site but five were for the fusiform-rust and one for the height traits on the Upper Coastal Plain site. All the significant contrasts selection stage produced an increment of gain rather than involved changes in the desired direction; that is, that loss. For cankers per tree, negative contrasts reflect the desired change, whereas positive contrasts are desired for the other traits. For the fusiform-rust traits, the only contrast showing an undesirable response to selection was that between the unrogued clonal orchard check and the commercial check (2 vs 1 , Table 1 ). The unrogued orchard check was more susceptible than the commercial check on both sites, though not significantly so. Apparently, selecting rust-free trees in natural stands did little to increase the proportion of rust resistance genes in the unrogued clonal orchard relative to that in natural stands. Later roguing and selection based on progeny test results have been effective in increasing rust resistance. Along with the increase in rust resistance has come little change in survival and only moderate improvement in height growth rate. However, selection after the initial stage has been primarily for rust resistance, so this result is not surprising. Selection for survival perse was not performed so the only survival response to be expected would be one that is correlated with a trait that was selected for, such as rust resistance. Such a correlated response in survival may appear as the trees get older and more rust mortality occurs. Contrasts between groups 1 (commercial check) and 6 (progenies from second generation selections) (Table 1 give estimates of total gains after two generations of selection. On the Upper Coastal Plain site, gain in the rustfree trait was 1 5.7 percentage points, or 53.6 percent of the check. The decrease in number of cankers per tree was 1 3.7 percent of the check. Also realized was an 1 1 .1 -- Table 1. Group means and contrasts between groups for fusj.form-rust, height, and survival at age 5 years of f.lash pine tested on two sites. Group and Contrast Rust- free Trait Cankers/tree Height Survival Upp;r Coastal Plain Site 1 Commercial check 29-3 2 Clonal orchard check 20.4 3 First-generation families 32.8 4 Seedling S.O. bulk (1976) 59-2 5 Second-generation bulk fami; .ies 42.6 6 Second-generation selections; 45.0 4.38 5-03 4.47 2.56 3.22 3-78 2 vs 1 3 vs 2 4 vs 3 5 vs 3 5+6 mean vs 3 6 vs 5 - 8.9 12.4 26.4 9.8** 11.0* 2.4 0.65 -O.56 -1.91* -1.25* -0.97** O.56 Flatwoods Site 1 Commerical check 94.4 2 Clonal orchard check 86.0 3 First-generation families 90.0 4 Seedling S.O. bulk (1976) 100.0 5 Second-generation bulk famil ies 91.8 6 Second-generation selections 92.5 0.10 .66 .12 .00 .10 .10 2 vs 1 3 vs 2 4 vs 3 5 vs 3 5+6 mean vs 3 6 vs 5 -8.4 4.0 10.0 1.8 2.1 0.7 O.56 -0.54* -0.12 -0.02 -0.02 0.00 #*( Significant at the 0.01 level h Significant at the 0.05 level 3.23 3.60 3-55 3.76 3-56 3-59 0.37 -0.05 0.21** 0.01 0.02 0.03 80.0 82.5 78.0 88.4 77-9 80.5 2.5 -4.5 10.4 -0.1 1.2 2.6 2.34 2.13 2.41 2.16 2.41 2.39 -0.21 0.28 -0.25 0.00 -0.01 -0.02 62.5 46.2 55-4 46.2 53-7 58.9 -16. 9-2 -9.2 -1.7 0.9 5-2 percent gain in height. In the plantation on the flatwoods site, the only gain was 2.1 percent of the check in height. Considerable variation in rust resistance still exists among first- and second generation families and among second-generation selections (table 2). Further gains should be possible with further selection and testing, especially in the plantation on the Upper Coastal Plain site where rust incidence has been quite high. Since very low rates of infection have occurred on the flatwoods site (Appendix tables 2-5), little opportunity for selection for rust resistance is expected in that plantation. Table 2. --The standard deviation among families within groups expressed as a percentage of the mean of the group for four traits at age 5 years. Family Families of firstgeneration clones Second-generation bulk families Families from secondgeneration selections Trait Plantation site Upper Coastal Plain Flatwoods -percent Rust- free Cankers/tree Height Survival 36.8 41.0 9-0 7-8 77-8 7-3 12.2 32.4 Rust- free Cankers/tree Height Survival 23.0 * 33-0 4.8 6.7 166.7 13.8 27.1 35-8 Rust- free Cankers/tree Height Survival 52.2 60.2 7-8 9-1 121.9 9-2 24.7 52.5 LITERATURE CITED Duncan, D B. 1 955. Multiple range and multiple F tests. Biometrics 1 1 :1-42. -- Appendix table 1. Description of progenies and check lots of slash pine. Progeny : or Check : GO^XW (60XP)XW,B (60XP)XW,S (60XP)XW,S (60XP)XW,S (60XP)XW,S 119XW (119XP)XW,B (ii9XP)xw,s (H9XP)xw,s (H9XP)xw,s Description 60 x wind (5-ramet mix) - First-generation family (60 x polymix) x wind (15-tree mix) - Second-generation bulk (60 x polymix) x wind - Second-generation selection (60 x polymix) x wind - Second-generation selection (60 x polymix) x wind - Second-generation selection (60 x polymix) x wind - Second-generation selection 119 x wind (5-ramet mix) - First-generation family (119 x polymix) x wind (5 - tree mix) - Second-generation bulk (119 x polymix) x wind - Second-generation selection (119 x polymix) x wind - Second-generation selection (119 x polymix) x wind - Second-generation selection 94xW (9itXP)XW,B (94XP)XW,S (94xp)xw,s (94XP)XW,S 50XW (50XP)XW,B (50XP)XW,S (50XP)XW,S 94 x wind (2-ramet mix) - First-generation family (9^4 x polymix) x wind (6-tree mix) - Second-generation bulk (94 x polymix) x wind - Second-generation selection (9^ x polymix) x wind - Second-generation selection (9^ x polymix) x wind - Second-generation selection 50 x wind (4-ramet mix) - First-generation family (50 x polymix) x wind (6-tree mix) - Second-generation bulk (50 x polymix) x wind - Second-generation selection (50 x polymix) x wind - Second-generation selection 20XW (20XP)XW,B (20XP)XW,S (20XP)XW,S 20 x wind (5-ramet mix) - First-generation family (20 x polymix) x wind (3~tree mix) - Second-generation bulk (20 x polymix) x wind - Second-generation selection (20 x polymix) x wind - Second-generation selection 71XW (71XP)XW,B (71XP)XW,S 6xw (6XP)XW,B 76XW (76XP)XW,B Check 1 Check 2 Check 3 Check 4 71 x wind (3-ramet mix) - First-generation family (71 x polymix) x wind (3~tree mix) - Second-generation bulk (71 x polymix) x wind - Second-generation selection 6 x wind (5-ramet mix) - First-generation family (6 x polymix) x wind (4-tree mix) - Second-generation bulk 76 x wind (4-ramet mix) - First-generation family (76 x polymix) x wind (4-tree mix) - Second-generation bulk Seedling seed orchard bulk - 1975 Seedling seed orchard bulk - 1976 Commercial seed collection (Georgia Crop Improvement Assoc.) Seed orchard collection (Georgia Crop Improvement Assoc.) 1/ Georgia Forestry Commission serial numbers for the first-generation selections. -- Appendix table 2. Significance tests for the various sources of variation in four traits at age 5 years in two slash pine test plantings analyzed separately and combined. Source of variation Trait Rust-free Cankers/tree Height Survival Upper Coastal Plain Site Replication Seed lot (all) First-generation families Second-generation families Second-generation selections Flatwoods Site Replication Seed lot (all) First-generation families Second-generation families Second-generation selections Two sites combined Site ** Replication in site ** Seed lot (all) * First-generation families Second-generation families Second-generation selections # Site x seed lot * # Significant at the 0.01 level Significant at the 0.05 level ** # *# ## * ** # * # Appendix table 3"--Means for rust, height and survival traits at age 5 years for wind-]pollinated families from f irst generation orchard clones of slash pine tested on two sites Family Rust- free Percent Trait Cankers /tree Number Height m Survival Percent Upper Coastal Plain Site 60XW 6xw 50XW 119XW 76XW 94xw 7ixw 20XW 54. 2a 4l.2ab 39-7ab 33-8ab 27.3ab 26.4ab 25.8ab 14. 2b 2.00a 5-50ab 4.44ab 5 . 58ab 4 . 22ab 3.l8ab 3 . 80ab 7.02b 3.91a 3.62ab 3.45b 3.46b 3.51b 3.38b 3.53b 3.54b 78.8a 75-Oa 79.9a 75-Oa 81.1a 80. 0a 78.1a 76.0a Mean 32.8 4.47 3.55 78.0 Flatwoods Site 6oxw 76XW 94xw 71.2a 20XW 6XW 50XW 119XW 71XW 98.6a 92.7a 92.3a 89.6a 89.3a 88.1a 88.0a 84.3a 0.02a .07a .09a .16a .14a .18a .14a .16a 2.46a 2.45a 2.30a 2.54a 2.26a 2.26a 2.62a 2.37a 56.2a 63.5a 44.4a 56.2a 34.6a 61. 2a 56.2a Mean 90.3 0.12 2.41 55-4 1/ Means followed tjy a common letter do not differ sign:Lficantly at the 0.05 level accordingI to Duncan s Multiple range test. Appendix table 4.---Means for rust , height and survival traits at age 5 years for seconds-generation bulk families of slash pine tested on two sites ' Family Rust- free Percent Trait Cankers/tree Number Upper Coastal Plain Site Height m Survival Percent (60XP)XW,B (71XP)XW,B (20XP)XW,B (6XP)XW,B (76XP)XW,B (119XP)XW,B (50XP)XW,B (94xp)xw,b 51.6a 50.4a 49.5a * 46.4a 40. 8a 36.2a 35.3a 30.4a 2.92a 2.74a 2.51a 2.11a 3.54a 3.10a 2.42a 6.44b 3.63a 3.58a 3.62a 3.63a 3.54a 3.6la 3.44a 3.40a 77.5a 81. 2a 77.5a 78.7a 81. 2a 82.5a 78.1a 66.2a Mean 42.6 3.22 Flatwoods Site 3.56 77-9 (50XP)XW,B (71XP)XW,B (119XP)XW,B (60XP)XW,B (20XP)XW,B (6XP)XW,B (94xp)xw,b (76XP)XW,B Mean 98.7a 95.6a 95.3a 95.0a 94.6a 93-5ab 85.1bc 76. 9c 91.8 0.01a .04a .05a .05a .05a .08ab .21bc .29c .10 2.19b 2.35b 2.09b 2.35b 2.40b 3.01a 2.62ab 2.28b 2.41 38.5a 57.5a 42.5a 42.5a 48.8a 69.5a 68.8a 61. 2a 53-7 1/ Means followed t)y a common letter do not differ at tile 0.05 level, according to Duncan's Mullsiple range test 3 BIDS D3Tlb 73b2 Appendix table 5-"--Means for rust, height and survival traits at age 5 years for progenies from the second-generation selections o f slash pine tested on two sites Family Rust-free Percent Trait Cankers/tree Number Height m Survival Percent Uppe>r Coastal Plain Site (60XP)XW,S (71XP)XW,S (60XP)XW,S (119XP)XW,S (20XP)XW,S (60XP)XW,S (50XP)XW,S (94XP)XW,S (20XP)XW,S (H9XP)xw,s (94xp)xw,S (H9XP)xw,s (60XP)XW,S (94XP)XW,S (50XP)XW,S Mean ?4. 8a 70. lab 68.1a-c 64.6a-d 52.5a-e 48.5b-f 48-5c-g 44.2d-g 42.4d-g 36.3e-g 31.3e-g 27-9e-g 26.5fg 25.0gh 17. 5h 45.0 1.52ab 1 . 26ab 1.25a 1.29ab 4.69a-d 2.54a-c 2.36a-c 4.92a-d 3-75a-d 7.86d 6.l6cd 4.99b-d 7.88d 2.97a-d 3-23a-d 3-78 3- 55a 3.65a 3.65a 3.51a 3.67a 3.73a 3.43a 3.30a 3.68a 3.76a 3.46a 3.69a 3.69a 3.66a 3.44a 3-59 77.5a . 96.5a 78.7a 82.5a 82.5a 75.4a 79.2a 86.2a 76.2a 75-Oa 80.0a 81. 4a 81. 2a 74.9a 80.0a 80.5 Flatwoods Site (60XP)XW,S (20XP)XW,S (60XP)XW,S (71XP)XW,S (50XP)XW,S (20XP)XW,S (H9XP)xw,s (60XP)XW,S (94xp)xw,S (60XP)XW,S (50XP)XW,S (H9XP)xw,s (H9XP)xw,s (94xp)xw,s (94xp)xw,S Mean 100.00a 98.2a 97.8a 96.4a 94.4a 94.1a 94.0a 93.3a 92.3a 91.5a 90.0a 88.8a 88.6a 85.6a 82.7a 92.5 0.00a .04a .04a .04a .06a .10a .14a .13a .09a .09a .10a .16a .11a .14a 30a 10 3.06a 2.12bc 2.42bc 2.05c 2.26bc 2.28bc 2.15bc 2.63a-c 2.24bc 2.73ab 2.19bc 2.4lbc 2.37bc 2.54ac 2 38bc . 2.39 69.6a 37.5b 71.2a 58.6ab 39.6b 52.5ab 48.8ab 72.3a 56.2ab 56.2ab 32.9b 52.3ab 58.8ab 6l.5ab 40. 0b 58.9 1/ Means followed by a common lett< to Duncan's Multiple range test. te 0.05 level, according GEORGIA F0RESTRY i John W. 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