籼粳稻杂种及其回交世代的遗传表现

Genetic Behavior of Indica-Japonica Rice Hybrids and Their Backcross Generations

分析了秀水117/IR58、矮农虎6号/IR36和矮在虎6号/IR5105等3个籼粳杂交组合的杂种及其双向回交世代的遗传表现.F_1的每穗粒数、穗长、单株穗数、抽穗天数和株高等性状一般表现较强的超亲优势,而千粒重则介于双亲之间.F_2及B_1F_1这些性状的变异幅度很大,并出现大量的超亲类型.随回交次数的增加,各性状的平均数逐渐向各自的轮回亲本回复,其变幅也依次缩小.这些性状的表现除受基因的加性或显性效应控制外,上位性效应也起着重要作用.模糊聚类分析表明,回交低世代的综合性状向籼稻亲本的回复速度比向粳稻亲本为快;而要在整体上基本回复到轮回亲本的面貌,至少需要回交三次.

Studies were carried out on the genetic behavior of 3 japonica/indica rice crosses, i. e. Xiu-Shui 117/IR58 (Cross I), Ai- Nong-Hu 6/IR 3G (Cross Ⅱ) and Ai-Nong-Hu 6/IR 5105 (Cross Ⅲ) , and the backcross generations produced by backcrossing the F1 hybrids of the crosses with japonica or indica parents once, twice and 3 times respectively. The Fl hybrids exceeded the higher parents in number of spikelets per panicle, panicle length, number of panicles per plant, days from seeding to heading and plant height, while their 1000-grain weight was intermediate between the higher and lower parents. Each of the F2 and B1F1 generations showed a wide range of variation, and a great number of individuals exceeding the parents were found. With the increase in the number of backcrosses, the means of the traits gradually approached those of the respective recurrent parents, and the variation lessened likewise. Apart from the additive or dominant effect, these traits were also controlled by the epistatic effects, which might be an important cause of the high F1 heterosis found between indica and japonica subspecies and the difficulty for the traits of the hybrid progenies to stablize. A fuzzy cluster analysis revealed that the overall performance of the traits of the early backcross generations approached the indica recurrent parents faster than the japonica ones. In order to restore the traits' behavior to that of the recurrent parents' as a whole, the Fl hybrids should be backcrossed with either indica or japonica parents at least 3 times.