Genetic Study On Two Maize Male Sterile Mutants Obtained By Space Mutagenesis And Their Mapping Using SSR Markers

Male sterility not only is an important tool to utilize heterosis in crops, to facilitate recurrent selection and population improvement,but also an important material to study pollen development,cytoplasmic inheritance and the interaction between cytoplasm and nuclear.Comparing with cytoplasmic male sterility,recessive genie male sterility has application potentiality in heterosis utilization in crops due to its special characteristics.In this study,Zheng 58 and Chang 7-2 male sterile mutants were obtained from the offspring of four maize inbred lines,which were carded into space by the Shenzhou spaceship 4.Their fertility was tested.The stability of their sterile characteristics in different generations,environments and genetic germplasms, and their genetic characteristics was analyzed.Thereafter,the nuclear genes were detected using SSR molecule markers combined with the bulked segregant analysis (BAS)method.Our objectives were to provide theoretical references and basic materials for further researches in fine mapping or even map-based cloning these male sterile genes,and revealing their expression,conducting marker- assisted selection and production utilization.The main results were as follows:1.No pollens or a few malformed pollens were observed in the anthers of male sterile plants for Zheng 58 and Chang 7-2.Both mutants were all completely sterile types.2.Crosses were made between the male sterile plants and the fertile plants from the same lines,and other normal inbred lines.The ratios of the sterile plants with the fertile plants in their F₁,F₂ and reciprocal backcross generations were calculated. Through analyzing forty-one crosses in four generations in three years and three seasons,it was considered that these two male sterile mutants were all controlled by a single nuclear recessive gene.3.Two mapping populations were developed to detect the genie male sterile genes,respectively.The F₂ mapping population for Zheng58 mutant was developed by crossing the Zheng58 sterile plant 5280(ms)with the Zheng58 fertile plant 5280(Ms) obtained through several sister-crossing generations of selection.While the F₂ mapping population for Chang7-2 mutant was obtained by crossing the Chang7-2 sterile plant 8057(ms)with a normal male fertile maize inbred Huang C.128 and 146 plants were included in the two F₂ populations.For the Zheng58 population,35 plants with complete sterile and 93 plants with complete fertile were observed.For the Chang7-2 population,32 plants with complete sterile and 114 plants with complete fertile were observed.The result ofχ² tests wereχ_c²=0.323＜χ_0.05,1²=3.84 andχ_c² =0.831＜χ_0.05,1² =3.84,respectively.They all fitted in with to the segregation ratio of 3:1.This further reflected that both male sterile mutants were controlled by a single nuclear recessive gene.4.According to the fertility observations in the field experiments and BSA method, polymorphism analysis were conducted using 418 and 386 pairs of SSR primers for the two F₂ populations,which were distributed in the 10 maize chromosomes.17 and 36 pairs of SSR primers with polymorphism were found,respectively.These polymorphic primers were further used to detect the genotypes of each F₂ plants. Linkage analysis showed that the two male sterility genes were located on chromosome 1 and 4 for Zheng 58 and Chang 7-2 mutants,respectively.SSR markers phi427913 and umc1160 were linked with the male sterility gene in the Zheng 58 mutant,and their genetic distances from the male sterility gene were 23.8cM and 19.4cM.However,the male sterility gene in the Chang 7-2 mutant was linked with phi006 and umc1109,with their respective genetic distances 18.0cM and 26.3cM.