Genetic Analysis And Fine Mapping Of Maize Genetic Male Sterile Gene Ms30

Maize（Zea mays L.）is one of the most important food crops in China.The yield of maize has been increased significantly by using heterosis,and male sterility plays a very important role in maize hybrid seed production.Genetic male sterility comes from lesions in nuclear-encoded genes disrupt normal male gametogenesis,with phenotypic characters of no anther exerted from tassel,and/or anther withered without pollen,and/or abnormal pollen development.In this study,based on the phenotypic identification,genetic analysis and gene mapping of ms30,a male-sterile mutant introduced from the United States,the following results were obtained:1、The phenotypic analysis of the ms30 sterile lines indicated that there is no significant difference between the ms30 mutant plants and normal fertile plants in the vegetative growth stage.While in the reproductive growth stage,the ms30 mutant plants can tassel normally,with abnormal male flower:the thin and yellow-whitish anthers,no cracked glumes,withered anthers and no anthers exerted from the tassel.Through microscope observation,there were no pollen grains to be found in the mutant anther.2、Based on the cytological observation of ms30 sterile lines,we found that the micro-spore cell wall of the ms30 mutant developed slowly in the early-vacuole microspore stage,with abnormal developed germination aperture.Then,the large vacuoles were found in mi-crospore accompanied with cytoplasmic degradation.Finally,only empty microspore wall could be observed,while the nucleus,cytoplasm and other contents had been degraded com-pletely,resulting to male sterility in mutants.3、Genetic analysis of the F₂ segregation population resulting from crossing the ms30mutant with the normal inbred lines of Chang7-2 and/or Zheng58,we found that all of the F1progeny was male fertile and the F₂ population displayed 3:1 segregation ratio of male fertile to sterile plants,suggesting that ms30 was a recessive genetic male-sterile mutant.4、The ms30 gene was genetic mapped by using a F₂ mapping population of ms30×Chang7-2.The linkage map of ms30 was constructed through testing the 295 sterile individuals with molecular maker analysis.The ms30 was initially mapped on chromosome4 between markers idp1991 and marker tidp9194 with the genetic distance of 2.9cM.Then,several novel polymorphic markers（such as ep462 and tidp374,etc.）were designed and analyzed.Finally,the ms30 gene was mapped to the physical interval of 41.2kb length between ep462 and tidp374.5、Analysis of the 41.2kb physical interval indicated that there were six putative genes including GRMZM2G174739,AC18643.4_PG003,GRMZM2G174782,GRMZM2G174797,GRMZM2G174834 and GRMZM2G174938.