The Study Of Creating Citrus New Germplasm By Sexual Hybridization And The Hybridization Influence On The Fruit Quality Of Majiayou And HB Pomelo

Citrus as a fruit of first production in the word, occupies an important position in the rural economy structure of south China. Its development not only affects the income levels of farmers in China, but also plays a significant role in China’s new rural construction. With the development of economy, people’s living standard and consumption level keep improving. Consumers have higher requirements for the quality and variety of fruit in the market, which makes the updating of the citrus varieties particularly important. In this study, a number of sexual offspring groups were created by sexual hybridization, which prepared materials for citrus hybrid breeding. Different hybrid combinations were created by using different pollen crossed with Majiayou(Citrus. grandis (L.) Osbeck) and HB pomelo (C. grandis (L.) Osbeck). By contrasting the fruit set and quality of citrus fruit of cross-pollination and natural pollination, the influence of cross-pollination to Majiayou and HB pomelo were studied. Specific findings are as follows:1. A number of sexual offspring groups were created by sexual hybridization. There were a total of1337diploid hybrids and64triploids offspring plants obtained.2. Hybrid offspring groups of "Clementina (C. clementina hort. ex Tanaka)×Jincheng(C. sinensis cv. Jin cheng (L.) Osb)"," HB pomelo (C. Grandis (L.) Osbeck)×Jiangxi seedless ponkan (C. reticulata Blanco cv. Ponkan)" and "Clementina×Jiangxi seedless ponkan" were identified and their hybrid rates were89.5%,97.8%and99.0%, respectively. The cluster analysis was performed between the offspring groups and parents of "HB pummelo×Jiangxi seedless ponkan" which found that with a similarity coefficient of0.72,88progenies could be divided into four categories.21progenies were in a group with paternal, accounted for23.9%of the total, and only six progenies were in a group with HB pomelo, accounted for6.8%. The other two groups were17and44plants, accounted for19.3%and50.0%, respectively.3. Two ways to create triploid were used here. One was using pollens of "4x Paper-Rind(C. sinensis Osbeck)" and "4x Grapefruit(C. paradisi Osbeck)" crossed with Majiayou and another was cultured embryos of small seeds, which were from crossing between diploid citrus with single embryo. Then, flow cytometry was used to identify the ploidy of the triploid. The former method had a higher rate to obtain triploid, about76.2%. However by the latter approach, none triploid had been found among the116seedlings that from hybrid combinations of "Clementina×Jiangxi seedless ponkan","HB pomelo×Jiangxi seedless ponkan","Clementina×Jincheng" and "Fallglo (C. reticulata Blanco)×Nanfengmiju (C. kinokuni hort.ex Tanaka)"4. To study the influence of cross-pollination to the fruit quality of Majiayou, we used Majiayou to cross with5different pollens, such as Shatian pummelo (C. grandis (L.) Osbeck), Longhuizao pummelo (C. grandis (L.) Osbeck) and others, and with natural pollination as a control. The qualities of the pollinated fruits were analyzed. It was found that the inner and outer fruit qualities among different pollination treatment fruits by cross-pollination and natural pollinated fruits were significantly different, such as fruit-set rate, single fruit mass, fruit shape index, peel thickness, seeds number, flesh recovery rate, total soluble solids, titration acid and Vc. It was shown that the fruit qualities of Majiayou were easily affected by the male parent pollen, and the metaxenia phenomenon was obvious found in Majiayou. The hybrid combination of "HB pomelo×Jiangxi seedless ponkan" was created and the fruits qualities of cross-pollination and natural pollination were analyzed. Compared with the natural pollination, cross-pollination fruits’external qualities, like single fruit mass, fruit shape index, seed number and flesh color, were of no significant differences. While the inner qualities, like vitamin C, titratable acid and soluble solids content of the natural pollinated HB pomelo fruits, were significantly higher than the cross-pollinated fruits. Therefore, it was better under natural pollination than cross-pollination for HB pomelo as a whole.