Variation in growth traits and early evaluation of the selection of intra and interspecific hybrid progeny of Pinus yunnanensis

Cross breeding is an important way to innovate germplasm. However, the growth performance of hybrid offspring is difficult to predict. Pinus yunnanensis is an important tree species for both timber and industrial raw materials in southwest China, and its genetic degradation is a serious concern. To accelerate the breeding process and diversify the genetic resources, 16 interspecific crosses of P. yunnanensis × P. kesiya and 22 intraspecific crosses of P. yunnanensis were evaluated and selected based on the systematic analysis of nutritional and reproductive growth traits. The results indicated that the differences in traits between the different combinations were significant, suggesting that the interspecific and intraspecific hybrid offspring showed high genetic variation with potential for selection. The interspecific crosses were considerably better than the intraspecific crosses for all phenotypic traits, indicating that the distant hybridization had an advantage of heterosis. Compared with the open-pollinated progeny, the progeny of superior hybrid family significantly improved in nutritional growth traits, and declined in reproductive growth traits. The coefficients of phenotypic variation, genetic variation, family heritability and individual heritability for the phenotypic traits were higher than other Pinus, indicating that the traits were highly variable and under strong genetic control. Nutritional and reproductive growth traits could be selected independently. Five interspecific crosses and one intraspecific cross were selected using a combination of the membership function and an independent selection method. Our findings provided an important material basis and theoretical support for hybrid breeding and genetic improvement of Pinus.