Application Of SSR Marker Techniques In Maize Varietal Identification And Protection

The paper studied the rapid identification technologe in parental lines of maize hybrids by SSR (Simple sequence repeat) markers, analysed the characteristics of genetics variation of the inbred lines and explored the heritance relation between inbred lines and EDV(essentially derived varieties), which were very important to varietal protection and selection(cultivation)of new inbred lines in maize. The main results were summarized as follows:(1)Based on 13 inbred lines and 10 pairs of reciprocal cross combinations, the new rapid DNA extraction method was explored from maize pericarp and the point that the maize pericarp DNA consists with their parent was confirmed by SSR markers. Moreover, the rapid identification technology of SSR in parental lines of maize hybrids was established, which can be used to amplify the DNA fingerprints database of maize hybrids.(2)Based on analysing 10 maize inbred lines from different place(sites) and year by SSR markers,the minimal genetics similarity coefficient was 0.944 in different year for the same inbred lines, average similarity coefficient was 0.99, which showed a small variation; The minimal genetics similarity coefficient was 0.923 in different place for the same inbred lines; average similarity coefficient was 0.969, which showed a small variation, too. It was studied that the variation may be due to geneitc variation and experiment technique.(3) The results showed that the distribution of similarity coefficient between individual and female parent of F8 resulting from more than 20 markers for Huangzao 4×Ye 107 and X178×B73 was the same as that from total markers for two populars by randomly sampling from the total markers of F2 and F8 of two populars, while, the results of 10 markers was distinct dissimilarity. The similarity coefficient between individual and parents of F2 and between individual and male parent of F8 of two populars by randomly sampling 10-60 SSR primers was the same as that of total markers for two populars, moreover, the means of similarity coefficient between parents and individual was distinct similarity for each sampling.(4) Based on studying the F2 and F8 of the two populars of Huangzao 4×Ye 107 and X178×B73 by SSR markers, the results showed that the probability of genetic similarity coefficient less than 0.75 was 100% between individual and parents, and the probability of similarity coefficient less than 0.8 was 100% between individuals, moreover, the similarity coefficient was also less than 0.8 beween the F2 and its homologous F8 individual in two populars. The minimal genetics similarity coefficient was 0.923 in the same inbred lines for 10 inbred lines from different place and year, however, the maximum similarity coefficient can reach 0.853 between present inbred lines by studying 50 maize inbred lines. The similarity coefficient between individual and parents was less than 0.75 selected from second cycle inbred lines, by which, individual selected from second cycle inbred lines can be seen as the new inbred line different from parental inbred lines. We can conclude the probability of similarity coefficient more than 0.65,0.7 and 0.75 between random amounts of individual and parents in RIL populars.