杂交水稻种子纯度的高低直接关系到杂种优势的大小。“三系”种子,经过多代繁育以后,由于本身的自然变异和分离,以及花期隔离不好,防杂保纯不严,加上机械混杂等原因,亲本有逐年变劣、退化的趋势。具体表现在:不育系的不育性下降,产生可育株或半可育株;恢复系的配合力减弱,恢复度不高;由此产生的杂交种子用于大田生产,生长参差不齐,结实率下降,种性退化,优势明显减退。实践证明,凡是使用经过提纯复壮和去杂保纯的亲 The purity of hybrid rice seed is directly related to the size of the heterosis. After many generations of breeding, the “three lines” of seeds tend to deteriorate and degenerate year by year because of their natural variation and separation, poor isolation of anthesis, and the strict protection against contamination and the complicated machinery. The specific performance is as follows: the sterility of sterile lines is decreased, resulting in fertile or semi-fertile plants; the combining ability of restorer lines is weakened and the recovery degree is not high; the resulting hybrid seeds are used for field production and have uneven growth , Seed setting rate decreased, species degeneration, the advantage was significantly reduced. Practice has proved that all those who use purifying and rejuvenating pure to go to miscellaneous health pro