Age Trends in Genetic Parameters for Growth and Resin-Yielding Capacity in Masson Pine

Masson pine (Pinus massoniana Lamb) has long been employed as a main source of pine resin in China. To get a better understanding of genetic regulation of resinyielding capacity (RYC), a total of 50 open-pollinated families of masson pine were planted at three testing sites for progeny testing. Investigation was conducted at ages 7, 9, 11, 13, 15, 20, 24 and 26 years to study inheritance, age-age genetic correlation, and early selection efficiency for RYC, height (HT), diameter at breast height (DBH) and volume of individual tree (VOL). Growth characteristics increased gradually with age. RYC had a rapid increase at early ages (before age 15) ficients of variations (CV) for four traits showed a decreasing trend with age and the decreasing rate was rapid at early ages and minor at later ages. Heritability for four traits was relatively stable with minor fluctuation. For across-age classes, heritability was the highest for height, intermediate for RYC, and lowest for volume and DBH. RYC had highly positive genetic correlations with three growth characteristics. Genotype-by-environment interaction for four traits was stronger at Yunan than at other testing sites. Age-age genetic correlations were high for four traits studied, reaching 0.7 after age 9 for most analyses. Early selection at age 13 was highly effective for height, age 15 for DBH and volume, and age 11 for RYC.