油菜是异花授粉作物,需要年年选种、留种,否则,再优良的品种连续种植二三年后也会出现退化、混杂现象,造成减产。采取哪种选种方法比较好,实践证明,利用主轴选种法选留的种子,比株选或片选的种子增产10%左右。这是因为,油菜主轴(特别是中部)角果开花、结果早,角果发育快,种子饱满,生活力强,播种后出苗率高,幼苗生长健壮,有良好的增产基础。主轴选种的具体方法是:在油菜黄熟期,选择中上部分枝多、角果密而匀称、健壮无病、长势及成熟一致的植株,剪下主轴,除去顶梢和下半部,留下中部角果,脱粒后晒干即可。选种的数量,可根据计划用种量确定,一般每 Rape is cross-pollinated crops, need year-long selection of species, to stay, otherwise, and then fine varieties of continuous planting two or three years will also appear degradation, mixed phenomenon, resulting in reduced production. Which method of selection is better, practice has proved that the use of the spindle selection seed selection of seeds, plant selection or chip selection of seeds yield about 10%. This is because rape spindle (especially in the middle) of the flowering fruit, early fructification, rapid fruit development, full seed, strong viability, seedling emergence rate is high, robust seedling growth, have a good yield base. Spindle selection of specific methods are: ripening in the yellow rapeseed, the choice of branches in the upper part, dense and symmetrical horn, robust disease-free, growth and mature plants, cut the spindle, remove the top and the lower half, leaving Under the Central Kok, threshing can be dried. The number of species selection, according to the plan to determine the amount of seeds, generally each