| Induced mutation was one of the important approaches for maize germplasm multification.The biological effects and their genetic variation of maize mutagenic progenies are analyzed to facilitate the effective selection and utilization of mutants.In this study,six wide-used maize inbred lines were mutated using 60Co-γRay Irradiation with three different dosages respectively to explore their radiation sensitivity and suitable radiant dosages.The biological effects on mutagenic progenies M1 and variation of the main characteristics of corresponding M3 lines were analyzed.Meanwhile,the genetic variation of 103 mutagenic progeniy M3 lines of inbred lines 48-2 and R08 were evaluated with SSR molecular markers.The major results are list as follows:1.Different maize inbred lines and their different characters had different radio sensitivities of 60Co-γRay irradiations.R08 was the most sensitive one among 6 inbred lines,followed by K305,K169, 698-3 and zheng 58,however,48-2 was the most insensitive one.The plant height,ear height and leaf area had great sensitivities to irradiation,followed by growth period,and the major tassel traits and ear traits had little radiation sensitivities.According to decline 30%of seedling height,the suitable radiation dose of K305 was 150-160Gy,that of R08,K169 and 698-3 were 165-175Gy,and that of zheng 58 and 48-2 were 180-190Gy and 200-210Gy respectively.However,in the breeding application of them,there must be real flexibility according to the actual objective and the radio sensitivities of various characteristics.2.The M1 plants of 6 maize inbred lines were restrained and lesioned remarkablely irradiated by 60Co-γRay.Such as the seedling rate and survived rate decreased,the growth stages were prolonged compared with its check,and the plant height,ear height and leaf area were restrained at different degrees and so on.The restrained and lesioned effects were larger as the radiation dosages increased. However,some of the major tassel and ear characters were restrained,but some of them were promoted. The main characteristics of M3 lines presented two-way's segregation compared with their checks respectively.The percentages of M3 lines with average values of plant height,ear height and leaf area were large than that of CK significantly,were higher than that of main tassel and ear characteristics. This phenomenon indicated that the mutation effects of the former were better than that of the latter.The variation range and coefficient of variation of various characters in the mutagenic progenies were increased,which indicated that radiation introduction could enlarge the variation spectrum of major characters in maize,and broaden the scope of selection.Additionally,7 mutant lines with kernel color changed and 4 mutant lines of male sterile were obtained in M3 generation of K305 and 48-2.3.The results of SSR analysis indicated that,the amplitude of polymorphism information content (PIC) of the 48-2 and R08 M3 lines were 0.307-0.948 and 0.108-0.955,and the average values of them were 0.762 and 0.701 respectively.The amplitude of genetic diversity indexes(H') were 0.552-2.830 and 0.254-3.309,and the average values of them were 1.830 and 1.777 respectively.The average value of genetic similarity coefficient of the 50 M3 lines of 48-2 with its check(M673) was 0.8194.Among them,the M723 was the lowest one and its value was 0.7327.The ear characteristics of this line had great difference with its original check.Followed by another 11 lines including M721 and M745 and the similarity coefficient of these lines were lower than 0.8000.The genetic variations of these lines were large compared with its check.The average value of genetic similarity coefficient of the M3 lines of with its check(M487) was 0.8373.Among them,the M499 was the lowest one and its value was 0.6929.The all characteristics of this line had great difference with its original check excpeted the numbers of ear rows.Followed by another 8 lines including M507 and M519 and the similarity coefficient of those lines were lower than 0.8000.The genetic variations of those lines had great difference with its original check.These results indicated that there were real genetic differences among those lines with different phenotypes.4.Inbred lines 48-2,R08 and their 103 M3 lines were clustered in 7 and 5 populations respectively based on the genetic similarity coeficient.The population including check inbred lines were the largest one among all populations.The numbers of M3 lines in it were 22 and 38 and the percentages were 44.0%and 71.7%respectively.The M3 lines in this population had little genetic variation with its original check.The genetic variations of other populations were relatively large compared with check, and plentiful genetic variations were presented among M3 lines in those populations,such as dwarf mutants,long and large ear mutants and so on.Therefore,the genetic basis of maize germplasm was broadened greatly.In breeding practice,we should enhance the selection and utilization of mutants based on the breeding objective and in accorded with the feature and regularity on genetic variations of main characteristics of mutant lines in various populations.So that,we may increase the breeding efficiency by means of radiation induced mutation in maize. |
PDF Full Text Request