【摘要】 在3个籼稻杂交组合的未经选择的高世代（F₆）群体中,选择有关农艺性状的极端选系,进行再杂交,并与原杂交组合相比较,以研究这些性状杂种优势的遗传机制和基因效应.结果表明:出穗期、株高、主穗一次校梗数和干粒重这4个性状的极端选系,能使同效基因的分布更趋向联合态,进而导致杂种的超亲优势消失.因此,这些性状在原杂交组合中出现的超亲优势,来源于显性同效基因的分散态.没有发现超显性和有利于杂种优势的上位性.但对每株穗数和产量两性状,由于对极端选系的选择未能产生增大两亲差异的效果,无法作出深入分析.更多还原

【Abstract】 Plant-lines with largest and smallest values for 6 traits with heterosis in F1 were selected in the unselected F6 populations of 3 original crosses in indica rice. And 6 new crosses between the selected plant-lines were made. In order to investigate the genetic mechanism of heterosis and gene effects, 6 generations, including P1 , P2, F,, F2, B1 and B2, were raised for each of the original and new crosses. The results obtained indicated that heading date, plant height, number of primary rachis branches and grain weight all showed heterosis over the better parent in the hybrid F1 of the original crosses,but such heterosis was not observed in that of the new crosses. It suggests that the heterosis in the originals is due to dispersion of genes of like effect in two parents. In the analysis of gene effect of these four traits, neither overdominance nor epistasis which is favourable to heterosis- was found. As concerns the traits of panicle number and yield per plant, further approach could not be done because plant-lines selection was nearly useless and the degree of association of genes was not enhanced.更多还原