水稻叶脉白化突变体wpsm的遗传分析与基因定位

叶绿素是植物生长发育必不可缺的元件。叶色突变体的发掘与研究在叶绿体发育、叶绿素代谢、光合作用等研究中具有重要作用。利用化学诱变剂EMS诱变水稻(Oryza sativa L.)籼型恢复系缙恢10号，从其后代中筛选出一份突变性状稳定遗传的叶脉白化突变体wpsm (white primary and secondary midrib)。与野生型相比，该突变体苗期表现正常，孕穗后期剑叶、倒二叶、倒三叶整张叶片的主叶脉和次级叶脉白化，叶肉细胞无显著变化，该性状一直持续到成熟期。抽穗期突变体wpsm的光合色素含量极显著低于野生型，净光合速率(P_n)及表观电子传递速率(ETR)极显著降低，株高、每穗实粒数、千粒重、结实率等农艺性状均显著降低。该突变性状受一对隐性核基因调控，利用892株西农1A/wpsm的F₂隐性定位群体，将该基因定位在第6染色体上引物InDel 10与InDel 4之间，遗传距离分别为0.06 cM和0.12 cM，物理距离约为56 kb。本研究为WPSM基因的克隆和功能研究奠定了基础。

Genetic Analysis and Gene Mapping of a Rice White Midrib Mutant wpsm

A white midrib mutant temparily designated as wpsm (white primary and secondary midrib) was screened out in the progeny of an excellent indica restorer line Jinhui 10 with seeds treated by ethyl methane sulfonate (EMS). The wpsm mutant displayed normal leaves during the seedling stage. In the late booting stage, the primary and secondary midrib of the first, second and third leaves of the wpsm mutant showed a bleached appearance, compared with those of the wild type, while mesophyll cells kept normal. This mutational character was maintained to maturity. The photosynthetic pigment of the wpsm was significantly lower than that of the wild type, so were P_n and ETR. Agronomic traits such as plant height, filled grain number per panicle, seed setting rate and 1000-grain weight were significantly decreased when compared with the wild type. Genetic analysis suggested that the mutational characters were controlled by a single recessive nuclear gene. Xinong 1A was crossed with the wpsm, 892 recessive mutants from the F₂ segregation population were used for gene mapping. WPSM was mapped on chromosome 6, between InDel 10 and InDel 4, with physical distance of about 56 kb. This result provides a foundation for WPSM gene cloning by map-based strategy as well as its functional analysis.