| Eucommia ulmoides Oliver,a dioecious plant that is the only member of the genus Eucommia(which is the only member of the family Eucommiaceae),is an economically important tree native to China.Although it is famous for its rubber and medicinal applications,it is also used widely in gardens and water and soil conservation.There has been a notable increase in E.ulmoides–based industries.Hence,to satisfy the increasing production demand sufficiently,superior E.ulmoides varieties should be directionally cultivated according to breeding targets like a high gutta-percha content,a high content of medicinal compounds,a high content of economically important compounds,high growth,high leaf yield,and leaf use,among others.However,there have been few multi-objective breeding studies of E.ulmoides.Furthermore,the genetic control of active component content of leaves,growth traits,individual leaf yield,and leaf morphological traits corresponding to breeding targets is not fully understood,which is a factor that restricts the progress of E.ulmoides breeding.With the breeding target through the whole text,the multi-objective breeding of E.ulmoides was studied systematically from the aspect of genetic parameter estimation of important traits,the establishment of target breeding index system,the crucial factor that affects the phenotypic traits variations,and selection of superior varieties.This study has provided a theoretical base to understand genetic control of important traits,a reference for the identification and evaluation of E.ulmoides germplasm,a path for the directional improvement of E.ulmoides,and germplasm for the selection of superior varieties.The main results are described below.1.The genetic parameters of active component content of leaves,growth traits,individual leaf yield,and leaf morphological traits of E.ulmoides were estimated.Eighteen E.ulmoides families obtained by controlled pollination of superior varieties or clones was treated as experimental materials,and the relevant traits of them were measured for 9 years continuously,indicating significant or highly significant differences in relevant traits among the families among years.The family heritability of these 10 traits was higher(mainly between 0.70 and0.99),indicating better performance could be obtained for important traits by family selection.The individual heritability of gutta-percha content was higher(0.88),indicating better performance could be obtained for gutta-percha content by individual selection.The general combining ability of ‘Xiaoye’ and ‘Daye’(among the female parents)and ‘Qinzhong No.1’and ‘Qinzhong No.2’(among the male parents)was higher for most traits among years.The special combining ability and the total combining ability of the “Huazhong No.2 × Qinzhong No.1” cross was higher for the growth traits and the total number of leaves among years.The special combining ability and the total combining ability of the “Daye × Luochao No.3” cross was higher for the crown diameter and the leaf area among years.The special combining ability and the total combining ability of the “Huazhong No.2 × Qinzhong No.2” cross was higher for the gutta-percha content of leaves among years.The 5a or 6a could be treated as the early selection time for growth traits,and 2a could be treated as the early selection time for leaf area.According to continuous measurement and analysis of the combining ability alongside the tree ages,family 11 was selected for superior growth and leaf yield,family 8was selected for superior leaf use,family 12 was selected for superior gutta-percha content,and family 19 was selected for superior chlorogenic acid content.2.The target breeding index system of E.ulmoides germplasm was established.Fifty-six E.ulmoides germplasm grown in the arbor cultivation model and 48 E.ulmoides germplasm grown in the leaf-oriented cultivation model were treated as experimental materials,15 leaf related traits including leaf morphological traits,the individual leaf yield,the active component content of leaves,and the leaf water status were regarded as the object of study,and the traits corresponding to target breeding were classified by probability grading method into 3 grades according to planting models.3.The main factor that affects variations in 12 important phenotypic traits(including active component content of leaves,growth traits,individual leaf yield,and leaf morphological traits)was revealed.Nine clones arranged in six experimental sites in China were treated as the research object.The effect and relative importance of the genotype,site,and genotype ×site interaction effects on these important traits were studied.The genotype and site effects had a significant effect on all the traits,indicating better performance can be obtained by selection of superior genotypes or cultivation areas.For most traits,the site effect accounted for a larger proportion of phenotypic trait variations.Correlation analysis of the 12 traits indicated that combined selection can be carried out among the traits within the growth or active component content of leaves,while cannot be carried out among the growth and active component content of leaves.Gray correlation and path analysis among the main environmental factors and the important traits revealed that the annual mean temperature and the annual sunshine duration were the main environmental factors that affected the traits.They correlated positively with the active component content of leaves and the leaf yield and correlated negatively with the growth traits.4.Superior individuals and superior clones for different uses were selected according to different breeding targets.Seven superior individuals,21 superior super seedling clones,8superior clones for a nationwide regionalization test,and 7 superior clones for a regional test in the Shaanxi province were selected.There was great improvement for them compared with contrast varieties and parents.Therefore,they provided sufficient materials for the selection of E.ulmoides varieties in different uses. |
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