甜瓜果实长度主基因+多基因遗传分析

Major gene and polygene inheritance analysis of fruit length in melon

甜瓜果实长度直接决定着果实的形状,是重要的外观性状,但其遗传规律尚不明确。为了探明甜瓜果实长度的遗传方式,以甜瓜长果种质(果形指数为12.0)、圆果种质(果形指数为1.0)构建六世代群体,采用主基因+多基因混合遗传模型研究春秋两季甜瓜果实长度的遗传规律。结果表明,甜瓜果实长度呈现典型的数量遗传,偏向圆果亲本遗传,受2对加性-显性-上位性主基因+加性-显性多基因控制(E-1模型)。主基因遗传效应以正向加性效应和负向显性效应为主,正向加性互作效应也较明显,但这3种遗传效应在季节间差异较大。第一主基因的主要遗传效应明显高于第二主基因。主基因在分离世代中的遗传率为42.67%~83.33%,多基因遗传率(26.57%)主要存在于春季B_(1:2)世代。因此,甜瓜育种过程中对果实长度的定向选择宜在早期世代进行。

Fruit length directly determines melon fruit shape. However, its inheritance has remained unclear to date. In order to dissect genetic pattern of melon fruit length, six genetic populations were constructed in the present study using two melon materials with contrasting fruit length, fruit shape index 12.0 and 1.0, respectively. The data collected from Spring and Autumn were subjected to genetic analysis with a mixed model of major gene plus polygene inheritance. The results suggested a typical quantitative inheritance of melon fruit length toward round-fruit parent. The optimal genetic pattern for melon fruit length fitted E-1 model, viz., two pairs of additive-dominance-epitasis major genes plus an additive-dominance-epitasis polygene. In this model, positive additive effect and negative dominant effect were observed as predominant effects with the two major genes and their positive additive interaction effect. However, these genetic effects were obviously different between the seasons. The first major gene had higher genetic effect than the second one. Major gene heritability varied from 42.67% to 83.33% in different populations, while polygene heritability(26.57%)was only detected in B_(1:2)generation in spring. Therefore, directional selection for fruit length in melon should be performed in early generation in breeding process. Our study revealed the genetic pattern of melon fruit length, providing a guidance for genetic improvement of fruit shape in melon.