玉米对干旱的反应取决于新陈代谢能力、形态结构和生育阶段.开花期逢遇干旱使玉米产量下降幅度最大.随着产量下降,环境方差所占比例增大,遗传力降低,直接选择效率不高.在干旱条件下,寻找遗传力高且与产量高度相关的第二类性状,构建选择指标,可提高耐旱选择效率.雌雄开花间隔天数(ASI)和单株穗数是可供利用的第二类性状,对其选择所获得的产量增益,在干旱和正常水分条件下均可表现出来.耐旱育种目的在于改变基因型对干旱环境的反应,实现耐旱丰产目标.根据目标环境特征,设计适宜的耐旱选择程序,结合分子标记辅助选择技术,鉴定和利用现有优良耐旱种质和CIMMYT耐旱群体,是我国进行耐旱育种和种质改良的可选途径。

The responses of maize plant to drought stress depend on metabolism,morphology and growht stage.When drought stress occure before or during flowering time,it strongly reduces grain yield in maize.The heritability and genetic variance for gain yield usually decrease as yieId levels fall,wihile experimental variances remain the same or increase, resultiing in efficient selection directly for grain yield.Under these conditions,selection for secondary traits,such as anthesis silking interval and ear per plant,may increase the selection efficiency.Breeding for drought tolerance is to improve the reaction of genotype to drought stress,and to reach hish yielding ability.The convetianal breeding approach combined with MAS for drought tolerance may efficently work based on the major feature of target area.At present,identiifcation and utilization of Chinese eltie and CIMMYT drought germplasm is the fast and efficient way for maize breeding for drought tolerance in China.