| The narrow germplasm base is the main factor limiting the success of corn breeding programs in China. In some regions, the local corn varieties may contain some desirable genetic features, and thus being considered as valuable germplasm resources for corn breeding. Due to the special geographical location of Shanxi Province, there is a large hilly area with a wide geographical diversity and significantly dispersed vertical height. In between the North China Plains and West China Plateau, Shanxi is the transitional region at where the predominant commercial crop changes from the Temperate Zone crops to the Frigid Zone crops. The terrains in Shanxi are complex. After a long-term cultivation, various corn varieties have developed into ecologically adaptive local corn varieties with diverse genetic variability, which are considered as rare germplasm resources. Therefore, the study and analysis on genetic diversity local germplasm resource in Shanxi play an important role in broadening the corn germplasm base. The SSR molecular marker technique based on DNA has many remarkable features, such as easy operation, higher polymorphism, co-dominant nature for most markers, moderate effect on the organism, no inevitable linkage between poor alleles, temporally and spatially independent and etc. Therefore, it is widely applied in various research fields, such as genetic diversity analysis and etc. In this study, both composite sampling approach and SSR molecular marker technique were employed to perform PCR gene amplification for38DNA samples of local varieties, based on48pairs of primes that homogeneously overlying10chromosomes in corn cell, and thus investigating the genetic diversities and correlations among the38local corn varieties in Shanxi. The results were as follow:1. By using the48primers, a total of368alleles have been detected due to the gene amplification done for the38local varieties. The number of alleles at each SSR locus ranged from2-16, with a mean of7.67; the average polymorphic information content was0.76, varying from0.24-0.89. The number of alleles detected by12#primer was16, which was the highest. A total of185rare alleles was detected, proportional to50.3%of the total allele number; the number of specific alleles was21, accounting for5.7%of total alleles.2.The local corn varieties from Qixian County had the most abundant genetic diversity, as at least41alleles have been detected by the48primers in each of the samples from the county. Specifically,47alleles were detected in "Qixian Small-head white corn","Qixian Sixty-day corn" and "Qixian Small White corn" respectively;42alleles were detected in "Qixian Baimaya Corn";43alleles were detected in "Qixian Baiyang Corn" and "Qixian Soft White Corn";41alleles were detected in "Qixian Baitu Corn".3. The coefficients of genetic similarity among the38local corn varieties ranged from0.87to0.53. In particular, both "Small White corn" from Jixian County and "Baimaya Corn" from Daning County had the highest coefficient of genetic similarity, which was0.87, indicating that a small genetic disparity between corn varieties in these two counties and a relatively less differed genetic base for germplasm. In contrast, both "Baimaya Corn" from Qinyuan County and "White Corn" from Heshun County had the lowest coefficient of genetic similarity, which was0.53, indicating that a large genetic disparity between corn varieties in these two counties and a relatively more differed genetic base for germplasm.4. By employing genetic similarity matrix, in combination with UPGMA cluster analysis, The SSR analytic clustering configuration of152hybrid samples was shown in Figure3.5. Through calculation based on matrix of genetic similarity coefficients among the152hybrid samples, the matrix of average genetic similarity coefficients for the38local varieties was obtained, and the clustering dendrogram of the38local varieties was shown in Figure3.6. By comparison, Figure3.6appeared to be a miniature version of Figure3.5. |
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