Cross-breeding In Tree Peony And Fertility Research Of Intersectional Hybrids

Tree Peony(Paeonia×suffruticosa Andr.) is a kind of famous traditional flowers in China, respected as "The King of Flowers".A variety of cultivar groups have been developed and the breeding of new cultivars has received more attention.Based on the wide collections from home and broad,in this study,we did a great deal of crosses in plenty parent combinations to research preliminarily cross-incompatibility and hybrid sterility.The main results are followed.1.A total of 224 combinations were crossed,2634 flowers were pollinated,14,101seeds and 3,654 seedlings were harvested,in which 11,162 seeds and 3,269 seedlings were obtained from close hybridization within infra-sectional(inter-subsectional) species,810 seeds and 34 seedlings were harvested from distant hybridization within infra-sectional(inter-subsectional) species and 2,129 seeds and 351 seedlings were harvested from distant hybridization between Sect.Moutan and Sect. Paeon.2.Average setting percentage of close hybridization within infra-sectional species was 21.30 seeds per flower.Setting percentage varied with species which was mostly affected by the fertility of the female parents but less by parent's compatibility.Average setting percentage of intra-sectional distant hybridization was low to 0.85 seeds per flower,which was influenced both by the fertility of the female parents and by parent's compatibility.Average setting percentage of inter-sectional distant hybridization was 2.39 seeds per flower,affected by the compatibility of parents.3.Average sprouting rate of infra-sectional close hybridization was 29%,and it was related to the sprouting vigor of female parents.Average sprouting rate of infra-sectional distant hybridization was extremly low,only 4%,which was caused by the reproductive isolation of parent materials.Average sprouting rate of inter-sectional distant hybridization was 16%.The results of reciprocal cross were obviously different,which was related to the female parent fertility and cross compatibility. 4.The fertility of inter-sectional hybrids(P.Ihoh hybrids as materials) was studied during the blooming period.The secretion of mucus was rapid and occured mostly in 2～3 days after flowering. Ovules began to shrink on the fourth day after flowring,and complete abortion finshed in about 10 days.Integument degradation occurred in the early period of development,and the growth embryo sac lagged behind,reaching micropylar end 10 days after flowering.The highly incoordination between nucella and integument may lead the abortion of ovule and cross-infertility.5.The inter-sectional reciprocal hybridization within Sect.Paeon and Sect.Moutan got 1,218 hybird seeds,in which hollow seeds account for 68%and sprouting rate was only 5%.It was the first time to take P.veitchii as male parent to crossbreed with tree Peony that had the mean setting percentage of 11.63 seeds per flower and the average sprouting rate of 13%.Consequently,P.veitchii had more potential and could be adopted widely in the distant hybridization of tree peony.