一个控制水稻籽粒长度主效基因--Lk-4(t)的BC2F2群体定位及其遗传效应分析

水稻籽粒大小和形状是影响稻米外观品质和产量的重要影响因素，对控制这些性状基因的定位和克隆有助于弄清籽粒大小基因的表达模式和相应的代谢系统，最终实现该性状的自由调控。运用SSR和CAPs标记对来源于蜀恢527//蜀恢527／小粒回交组合BC2F2群体800隐性长粒单株进行分析，定位了一个控制水稻籽粒长短的基因，Lk-4（t）。对F2和BC2F2群体籽粒大小形状和千粒重的遗传分析表明，回交能将大部分对目的基因效应具有干扰修饰作用的微效基因多态性除去，从而有利于对目的基因型的准确鉴定；在F2和BC2F2群体中只发现两类籽粒长短表现型，即短粒和长粒，并且二者分离比例符合3：1的典型一对等位基因分离比例。这说明群体中籽粒长短变异是受一对基因控制。通过对BC2F2群体中隐性（长粒）单株进行分子标记分析，将这个控制籽粒长短的主效基因定位在3个CAPs标记，P1-EcoRV，P2-SacⅠ和P3-MboⅠ附近。连锁分析表明，Lk-4（t）位于水稻第3染色体着丝粒附近，离标记P1-EcoRⅤ和P2-SacⅠ分别有0．90cM和0．50cM的距离。

Genetic Analysis and Physical Mapping of Lk-4(t), a Major Gene Controlling Grain Length in Rice, with a BC2F2 Population

Grain size and shape are important factors affecting grain quality and yield in rice. Mapping, tagging and identification of their related genes can lead us to understand their expression pattern and mechanism network, which is to their control. In this study we mapped a grain length controlling gene named Lk-4(t) with SSR and CAPs markers by screening 800 recessive plants in a BC2F2 population derived from a cross of Shuhui527×Xiaoli and backcrossed with Xiaoli as the donor parent. The distribution of grain shape parameters and thousand grain weight in F2 and BC2F2 population showed that backcross can diminish most unnecessary variations to identify the target gene more clearly. There were only two grain length phenotypes found among the 3 209 BC2F2 plants, long and short, indicating it is a qualitative trait. The frequency distribution for the grain length showed a typical segregation ratio of 3:1, suggesting that only one allele was responsible for the variation. By screening the recessive long grain plants with three CAPs markers, P1-EcoRV, P2-Sac Ⅰ and P3-Mbo Ⅰ, we tagged the locus on the arm of chromosome 3 near the centromere. Lk-4(t)was located between P1- EcoRV and P2-Sac Ⅰ, with genetic distance of 0.90 cM and 0.50 cM from the two markers respectively.Mapping of the gene is a foundation for its final identification and function analysis.