Genetic Variation Analysis In Maize Mutants From AS-9Inbread Line Based On SSR Marker

The essence of evolution is to select natural variation among species. The frequency of spontaneous mutation ranges from one in a million to one in ten thousand, so people take advantage of all kinds of means which can induce mutants efficiently and effectively in order to achieve valuable mutants or species of good quality and great quantity in short period. In this study, Zea mays inbred line AS-9was chemically induced and then the genetic variation was analyzsed by sequencing technique and SSR marker technique. The results were as follows:1. The strategy of sampling and improved SSR marker experimental system. Genome DNA extraction method and SSR-PCR amplification system were improved. Dipping the PCR products by pipette in the first PCR, and taking it as template for the second PCR of10cycles, it turned out that the number of untargeted bands was smaller than that before. SSR marker examination indicated that there was no significant genetic variation among different leaves which grew on the same plant of induced maize inbred line. Polymorphism in SSR examination of grains from different parts in one single spike was observed, so sampling leaves from different seedlings was quite necessary for the genetic variation analysis for the mutants.2. The comparative analysis of germination and salt tolerance between the mutants and their inbred parent strain. Significant difference of germination rate, the length of shoots, and the number of roots were detected between mutants (M1&M4) and the corresponding basic material(AS-9). Salt tolerance was different between the mutants and the inbred parent strain when the root length and the seedling height were selected as the parameters. The root number of IV400was increased by23percent; the root2and root3of Ⅳ1600were0,69and1.16times larger than basic material. To sum up, the chemical mutation changed the activity of seeds and their ability of generating roots were enhanced, which improved their ability to fight against stresses.3. Genetic variation of the mutant offspring.Making SSR analysis for the M1and M4generation with the help of54pairs primers,the mean value of genetic similarity ratio between M1and the parent inbred line was0.3647whereas the mean value between the M4and the parent inbred line was0.4346. With the certered genetic similarity coefficient of-0.02by UPGMA,the maize mutants were divided into four groups. The results indicated that there was distinct variation among mutants,so maize inbred line AS-9had produced a wide range of genetic variation by the chemical mutagenesis. Compared to the sequence from database, the length variation of SSR-PCR amplification products was the result of changes in SSR repeat motifs and repetitions. Further study is required to confirm the function of the gene in which the sequenced fragment was included.