| In this experiment, seven inbreds which had different genetic backgroud together with seven hybrids breded with them were studied to find the agronomical, physiological and genetic mechanism of heterosis performance. The aim was to provide theoretical basis for heterosis utility, parent selection and heterosis prodiction. The result were as follows:1. Correlation analysis between agronomical characters and heterosis performance in the hybrids indicated that the fruit number per plant, fruit weight, fruit growth rate, female flower number, percentage of fruit setting, early yield per plant, early fruit number per plant, early fruit weight length of fruit and diameter of fruit all had positive correlation with the yield per plant at significant or very significant level. The hybrids showed positive mid-parent heterosis and even super-parent heterosis in these characters. Among them, the heterosis of the yield per plant and the fruit growth rate were much higher, whose mid-parent heterosis index reached 1.61, and super-parent heterosis index reached 1.53 and 1.47 respectively. However, the period from planting to flowering and from planting to first harvesting. had negative relationship with the yield per plant and the hybrids showed negative heterosis. Their mid-parent heterosis index were 0.96 and 0.97 respectively. In a word, all of the characters which were closely correlated with the yield per plant had heterosis performance compared with their parents, this may be the agronomical basis of heterosis forming.2.In the stage of seedling, middle fruiting and end fruiting, the correlation coefficient between the photosynthetic rate and the yield per plant reached significant even very significant level. The hybrids all performed positive heterosis and the heterosis were especially prominent in the stage of seedling and end fruiting. In different stages, the leaf area all correlated with the yield character at significant or even very significant level. The hybrids showed positive heterosis in the whole life. The character of chlorophyll b in the middle fruiting stage and the chlorophyll a/b in the end fruiting stage were significantly and positively correlated with the yield character and the hybrids hadheterosis performance. In conclusion, the hybrids had larger leaf area, they could utilize light especially weak light more usefully, and in the growth stage long the plant could always maintain higher photosynthesis rate, which may become one of the important physiological basis of heterosis performing.As for the dry matter content in the plant, he hybrids all showed heterosis performance compared with their parents at different level in the whole growth stage. The heterosis performance were especially obvious in the three fruiting stage, whose heterosis index were all above 1.40. In the former growth stage, the dry matter in the vegetation organ of the hybrids showed strong heterosis compared with their parent, so did that in the fruit organ during the middle and end fruiting stage, which may be another important course of yield hetersosis forming.From the analysis of the nitrogen, phosphorus and potassium nutrition accumulation and division, we could see that during the former growth stage, there were not much difference between hybrids and their parents, while in the fruit stage, the hybrids absorbed the nutrition faster and more stably than their parents. In the early growth stage, the nutrition accumulated in the vegetation organ and in the latter stage that in the fruit of hybrids all showed great heterosis. So, the hybrids could utilize the nutrition more rationally and efficently. These may help to form yield heterosis.3. The negative but not significant correlation between the genetic distance and parents showed that it wasn't the case that the greater the genetic distance were, the better. The relationship between hybrids and their parents indicated that the performance of agronomical characters in the hybrids were all affected by their parents at different level, so the heterosis... |
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