前言据报导,自然选择能显著改变小粒谷物的异质群体。在基因型竞争条件下,不同基因型的生存优势与繁殖效率有关,而在纯种栽培条件下这种关系存在的可能性较小。Khalifa等曾报导过种植在加利福尼亚州的高秆和半矮秆小麦(Triticum aestivum L)的品种混种群体,产量明显下降。他们认为,在选择之前应特别注意排除基因型之间竞争作用的影响。Khalifa等报导了过去研究的高秆和半矮秆小麦的杂种集团世代,发现从F_2—F_(?),高秆植株逐步增加而矮秆植株不断减少,但是和品种在混播的条件下的结果相反,杂种集团由F_2—F_(?)的籽粒产量却不断增加。在大麦(Hordeum Vulgare L)中也有类似的报导。Tennings等亦报导过,若与竞争性的高秆植 Preface It has been reported that natural selection can significantly alter the heterogeneous population of small grain cereals. Under genotypic competition, the survival advantage of different genotypes is related to the reproductive efficiency, but this relationship is less likely to exist under pure-cultivation conditions. Khalifa et al. Reported that a mixed breed of high-stalk and semi-dwarf wheat planted in California (Triticum aestivum L) significantly reduced the yield. They believe special attention should be given to eliminating the effects of competition between genotypes before choosing. Khalifa et al. Reported the generation of the hybrids of high-stalked and semi-dwarf wheat that were studied in the past and found that the number of dwarf plants decreased from F_2-F_ (?) In contrast, the grain yield of F 2 -F_ (?) Hybrids increased continuously. Similar reports have also been made in Hordeum Vulgare L. Tennings et al. Have also reported that, if competing with tall stalks