从异地引入的小麦良种,由于环境条件变化等因素的影响,会发生这样或那样的变异;一个种植了很久的农家品种,群体内的变异个体更是多种多样。这些变异的个体中,有不良的变异个体,也有优良的变异个体。不良的变异,会造成良种退化;优良的变异,可以选育成新的优良品种。因为变异是创造新类型的基础,选到一个好的变异个体,经过选择和培育,就有可能成为一个新的优良品种。利用现成的自然变异,选育新品种的方法,叫“优中 One kind or another mutation occurs in the wheat varieties introduced from different places due to environmental conditions and other factors. For a long-term cultivated varieties of farmers, the variation individuals in the population are more diverse. Among the individuals with these variants, there are undesirable variants and individuals with excellent variants. Bad variation, will lead to degenerative varieties; excellent variation, can be bred as a new fine varieties. Because variation is the basis for creating new types, choosing a good variation individual can make it a new good by choice and cultivation. The use of readily available natural variation, breeding new varieties of methods, called "excellent