Controlled Hybridization And Molecular Identification Of Hybrids By SSR In Chinese Jujube

No cultivars from hybridization have been used in cultivation of Chinese jujube as a result of its undeveloped cross breeding. Two obstacles, difficult manual pollination and embryo abortion, hindered Chinese jujube cross breeding. Chinese jujube has very small flowers with a diameter of 3-6 mm. Emasculation should be carried out before buds dehiscece because of proterandry in Chinese jujube. So, severe damage to flower is inevitable during manual pollination, which usually causes failure of manual hybridization. Embryos are abortive in most of Chinese jujube cultivars, especially excellent cultivars possibly used as parents in cross breeding. To overcome these obstacles, cultivars with the traits of high embryo rate and male-sterility or selfsterility could be used parents. Controlled hybridizations including several parents such as female parent JMS2 and male parent ‘Wuhefeng’ were achieved in this study. Authentic hybrids were identified by SSR markers. The approach has potential for mass production of hybrids. The main results are as follows.1 Controlled hybridization of Chinese jujube had been conducted in Xinjiang from 2013 to 2014. A total of 3548 fruits with 530 kernels were harvested in 14 crossing combinations by honeybee aided pollination in a net. Differences of fruiting and the rate of fruit with seed obviously changed among cross combinations and years. The rate of fruit with seed of all the combinations in 2014 was lower than that of 2013. Differences of cross compatibility was significant among combinations. The rate of fruit with seed in JMS2 × J5 in 2013 was 78.51% and it was only 12.13% in 2014. The rate of fruit with seed in JMS2 × Xing16 was 81.61% and 14.68% in 2013 and 2014, respectively. Compared to other cross combinations, JMS2 × J5 and JMS2 × Xing16 could be used in Chinese jujube controlled hybridization because of high embryo fertility and cross compatibility in both combinations.2 A total of 991 fruits were harvested from the two cross combinations JMS2 × J5 and JMS2 × Xing16, but they only contained 274 embryos, of which 128 from JMS2 × J5 and 146 from JMS2בXing16. Hybrids was identified by SSR markers. Two pairs of complementary parental primers, JSSR244 and JSSR311, were screened from 200 pairs of SSR primers for hybrid identification in two cross combinations, respectively. 58 of 59 progenies were identified as true hybrids in JMS2×J5 and all of the 126 progenies were identified as authentic hybrids in JMS2 × Xing16.3 Effects of materials sources, transition time and rooting ways on transplanting were evaluated. Differences of the survival rate of plants was not significant among different transition culture time. The survival rate of plants in JMS2 × ’Xing16’ was not significantly different from that in natural offspring. However, the survival rate of own-rooted seedlings was higher than that of the subculture rooted plantlet and reached 93.83%. Plants after culture in light incubator had a higher survival rate than those cultured in greenhouse and the rate reached 93.31%.4 Morphological characteristics of transplanted progenies were investigated 1 year later. Traits of offspring such as plant height, branch spread from east to west, branch spread from north and south, basal diameter and leaf index were significant different between controlled hybridization and natural hybridization. Except for plant height and intermodal length, there were no significant differences of most traits of progenies between JMS2 × ’Xing 16’ and JMS2 × J5. It may be a result of the same female parent. There were differences of traits among individuals obtained by micropropagation. In addition, a male sterile progeny was acquired by investigation of flowering traits.