Using Physiological And Biochemical Methods And RAPD Marker For Predicting Heterosis In Watermelon

In this study 9 heterotic hybridized combinations of watermelon and 18 watermelon parents were used as experimental materials. We used the correlations between watermelon hybrids and their parents for selecting some physiological and biochemical indexes which could be related to watermelon heterosis. The selected physiological and biochemical indexes were used to predict heterosis potential of 18 watermelon parents, then RAPD marker was used to verify the predicted results. The main results were as follows:Firstly, homogenized method was used for watermelon crossbreeding firstly. The results indicated that homogenized parental seedlings of watermelon had significant correlations with watermelon hybrid vigor. We selected three ones which could predict watermelon heterosis among many physiological and biochemical indexes. The three indexes were chorophyll a content of coyledon, the ratio of chorophyll a content and chrophyll b content of euphylla and soluble protein content of euphylla. According to the correlations among watermelon parents, hybrids and homogenized parents, we deemed the three indexes of homogenized parents could substitute for the three ones of watermelon hybrids and were used to predict watermelon heterosis.Second, in accordance with the correlations among watermelon parents, hybrids and homogenized parents, we drew a diagram of the procedure for selecting physiological and biochemical indexes, and defined threshold values of three indexes. The threshold values were as follows:Chorophyll a content of coyledon(unit:mg/g fruit weight): 0.604-0.931 The ratio of chorophyll a content and chrophyll b content of euphylla: 2.820-3.190 Soluble protein content of euphylla(unit:ug/g fruit weight): 29356-36447 Third, we used the three indexes and threshold values for predicting heterotic potential of 18 watermelons.81 combinations were found to be potential, specially 6 hybrid combinations were attained in the light of the three indexes which were selected. They were 2+6,2+7,2+11,2+13,5+9 and 13+20, respectively.Forth, among 20 primers, 8 were found to amplify polymorphic products in this study. 112 of the total products were found to be polymorphic. The results of cluster analysis by using UPGMA method also showed that 18 watermelon parents were classified to four groups in accordance with genetic distance of 18 watermelon parents.Fifth, the results which were verified by RAPD marker showed that soluble protein content of euphylla of the three indexes was accurate, the percentage of accuracy was 81.81 percent. We used the ratio of chorophyll a content and chrophyll b content of euphylla and soluble protein content of euphylla together for predict heterosis. 85.71 percent was accurate. If the three indexes were used together to predict watermelon, the percentage of accuracy was 100 percent. From those we known that the criterion of selecting procedure was more rigorous, the percentage of accuracy was higher.Postgraduate: Xia Yan Specialty: Olericulture Supervisor: Vice-prof. Yu Xihong...