| In this study, the aim was to provide a suitable, simple and feasible method of cross breeding for Heilongjiang area by constantly groping the method to effectively improve hybrid technology in alfalfa's sexual hybridization. Using parent's good traits provide the theoretical basis for alfalfa parent selection and heterosis prediction. The results are as follows:1. The feature of florescence of alfalfa: alfalfa's flowering period was from early September to early June influenced by the weather and it generally bloomed from 6:00 to 20:00 every day in Heilongjiang. Florescence:â… was the period of the whole inflorescence gathering, the floret not separating, and the best time to observe meiosis.â…¡w as the period of the floret separating and the calyx packaging the petals.â…¢was the period of petals appearing between the calyx, but their length did not exceed more than 2mm.â…£was the period that the petals were over the calyx 2mm or more, but the keel was still wrapped by the vexil.â…¤was the period that the keel has appeared from the ventral surface of the vexil, but the keel has not turned yet.â…¥was the period that the flowers open, the keel has turned, and the keel has appeared from the wing.2. The determination of alfalfa's pollen viability: using four methods determinate alfalfa's pollen viability. The results showed that I2-Kidyeing,TTC dyeing and red ink dyeing aren't suitable for determination, but in vitro culture method could determinate pollen viability quickly and accurately. Agar method (10% sucrose, 0.015% boric acid and1% agar) and hanging drop method (10% sucrose and 0.015% boric acid) were accurate and rapid determination of pollen viability, but the hanging drop method was more convenient. We could gain the best observed time when cultivate pollen by 1.5h.3. The study of medthod of crossing breeding:(1)It's found that fromâ… toâ…¢the alfalfa's pollen is not viable and fromâ…£it's viable in the test of determination. In artificial emasculation,â…¢was the most appropriate.(2) Comparing the effect on setting rate by hot water emasculation, chemical emasculation and artificial emasculation, it is found that the setting rate were 35.33%,11.33%,9.33%.The result of artificial emasculation was significantly higher than others.And the medthod of hot water emasculation did not apply to alfalfa's cross breeding. Therefore, the most appropriate method was the artificial emasculation.(3) Experimental results showed that in order to obtain the highest possible rate of hybrid seed, we should choose emasculation and pollination at the same day. In the sunny days, at 8:00 ~ 17:00 the artificial hybrid operation should be made, 10:00 ~ 17:00 could be use to get a higher seed rate, and 11:00 ~ 12:00, 14:00 ~ 15:00 could get the highest seed rate.(4) Improved crossing method could effectively improve the hybridization efficiency of alfalfa.6. The reciprocal cross test: the setting rate in orthogonal test was higher than in the reciprocal cross test, which Zhaodong alfalfa was female parent and Pleven6, Beza87, WL323HQ were male parent respectively. The combination of Zhaodong alfalfa and WL323HQ gained the highest setting rate. Male parent's pollen viability in range of 40% to 70% has little effect on the setting rate. |
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