Genetic And Combining Ability Analysis Of The Third Generation Germplasm Of Pinus Massoniana

Pinus massoniana is the main conifers native tree species in the south china with quality performance of wide distribution rage,fast growth and strong resistance of droughty and poor soil,and uesd widely in building,papermaking and resin tapping.Comprehensive genetic improvement of Pinus massoniana in our country had began in 1980 s.And now we have finished the second generation genetic improvement stage and are mounting to the new phase of the third generation genetic improvement stage.In the present study,three test materials of the third generatoin germplasm of Pinus massoniana were used to analyze the genetic variation of growth traits and oleoresin traits,and the interaction of genetic effects with environment on growth traits and the correlation in oleoresin components and the correlation between oleoresin compounds and growth traits were also investigated.At the same time,based on the SSR markers,the genetic diversity and genetic distances of breeding parents were analyzed.And the relationships between heterosis and combining ability,genetic distance were also investigated to improve the efficiency of parental apolegamy and the utilization of heterosis and will provide scientific and effictive theory basis for the advanced generation genetic improvement of Pinus massoniana.The results are as follows:1)Two test materials of 3-year-old Pinus massoniana grown in laoshan forest farm of Zhejiang Province and weimin state-owned forest farm of Fujian Province were used to investigate the genetic effects and the interaction of genetic effects with environment on growth traits in the 6×6 half diallel cross design.Results showed that the combining ability and the interactions of combining ability with environment were significant effective in the height and DBH.And most growth traits were cotrolled mainly by the additive gene effects.The performance of tree height,DBH were controlled mainly by the environment effects and secondly by the additive gene effects and the interactions of dominance gene effect with environment and the dominance gene effects,the interactions of additive gene effect with environment played a weakest role under different environment condition.The general combining ability(GCA)stability was significantly higher than the specific combining ability(SCA)stability.Based on tree growth index,2 superior parents and 5 superior combinations were preliminarily selected with favourable genetic gains for the two test materials respectively.2)A half diallel cross among 6 Pinus massoniana clones in Laoshan forest farm of Zhejiang Province was used to investigate the genetic variation of oleoresin components,the correlation in oleoresin components and the correlation between oleoresin compounds and growth traits for Pinus massoniana.Results showed that 23 oleoresin components were identified.And the genetic effects of GCA were more significant than the genetic effects of SCA in the 13 major oleoresin components with higher average content and significant differences among the combinations.Most major oleoresin components were cotrolled mainly by the additive gene effects while Dehydroabietic acid was cotrolled mainly the by dominance gene effects and Levopimaric acid / Palustric acid,8,12-Abietadienoic acid were cotrolled by the additive gene effects and the dominance gene effects simultaneously.And he 13 major oleoresin components were under moderate or high level genetic cotroll.In addition,higher positive correlations were found between ?-pinene,camphene and ?-pinene in Monoterpenes,which means the selection of one component can make the same increase or decrease for the other components.However,Levopimaric acid/Palustric acid in Diterpenes were found higher negative correlations with most major oleoresin components of Monoterpenes,Sesquiterpenes and Diterpenes components,and the extremely significant negative correlations were found between between Levopimaric acid/Palustric acid and Longifolene,Pimaric acid,Dehydroabietic acid,8,12-Abietadienoic acid,Abietic acid,Neoabietic acid,which mean the selection of Levopimaric acid/Palustric acid will restrain the increase of most major oleoresin components.Meanwhile,it was found that most major oleoresin components and growth traits were hardly relevant.So we speculate that the two types of traits may be controlled by different genetic mechianism and independent selection for the two types of traits can be used in the breeding.3)Two test materials for the third generation of Pinus massoniana grown in Laoshan forest farm of Zhejiang Province were used to investigate the relationships between heterosis and combining ability,genetic distance.Results showed that the phenotypic value and heterosis of growth traits exhibited significant differences,and the combining ability of most growth traits were also significant in the two test materials.Most growth traits were cotrolled mainly by the additive gene effects,and the growth traits were under high level genetic cotrolled.The genetic diversity of the 12 breeding parents was under moderate level.And the relationship analysis showed that most correlations between phenotypic value,heterosis of growth traits and combining ability,genetic distance were significantly positive.Among the GCA(P1+P2)?SCA and GD of the parents,GCA(P1+P2)was proved to have the strongest ability to predict the phenotypic value of growth traits,SCA was proved to have the strongest ability to predict the heterosis.In summary,it is feasible to predict the phenotypic value and heterosis of growth traits by combining ability and genetic distance to improve the efficiency of parental apolegamy and the utilization of heterosis for Pinus massoniana.