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利用微卫星(SSR)标记技术和DNA混合取样方法,选取均匀覆盖玉米染色体组的42对SSR引物,检测了来自我国西南地区54个玉米地方品种的遗传多样性。在54个玉米地方品种中检测到256个等位基因,每个SSR标记的等位基因数为2～9个,平均6.1个,说明我国西南地区玉米地方品种遗传多样性丰富。根据遗传相似系数矩阵做出的树状图,将54个玉米地方品种大致划分成4类,来源于同一地区的多数玉米地方品种划分在同一类中,表明西南地区玉米地方品种的地理分布与其遗传背景存在内在联系。从54个玉米地方品种中选出11个,每个品种选取15个单株,共165个DNA单株样品,分析玉米地方品种的遗传结构及其品种内的遗传多样性。对于检测玉米地方品种的遗传多样性,DNA单株样品分析优于DNA混合样品分析,42对相同的SSR引物在11个玉米地方品种中检测到330个等位基因,平均等位基因数A=7.86,有效等位基因数Ae=3.90,平均期望杂合度He=0.69,实际观察杂合度H0=0.37。据遗传结构分析结果,固定指数(F)为0.25～0.79,表明玉米地方品种是典型的混合繁育系统;由于杂合体不足,玉米地方品种群体间及群体内的遗传结构均偏离了Hardy-Weinberg平衡;杂合性基因多样度比率(Fst)平均为0.07,表明品种间和品种内的遗传变异分别占总遗传变异的7%和93%。玉米地方品种内遗传多样性及品种间遗传距离分析结果表明,在我国西南地区,分布在四川的玉米地方品种具有最丰富的遗传变异。经综合分析推测,我国西南地区玉米地方品种最早引进到四川种植,由此向毗邻地区传播扩散。
A total of 42 pairs of SSR primers were used to detect the genetic diversity of 54 maize landraces in southwestern China using microsatellite markers (SSR) and DNA hybrid sampling. 256 alleles were detected in 54 maize landraces. The number of alleles per SSR marker ranged from 2 to 9, with an average of 6.1, indicating that the genetic diversity of maize landraces in Southwest China is plentiful. The 54 maize landraces were divided into four categories based on the tree map of genetic similarity coefficient matrix. Most of the maize landraces from the same area were grouped in the same category, indicating that the geographical distribution and genetic inheritance of maize landraces in Southwest China Background is intrinsically linked. Eleven of the 54 maize landraces were selected, and 15 of them were selected for each variety. A total of 165 DNA single plants were selected to analyze the genetic structure of maize landraces and the genetic diversity within their cultivars. For the genetic diversity of maize landraces, DNA single sample analysis was superior to DNA mixed sample analysis. Of 42 identical SSR primers, 330 alleles were detected in 11 maize landraces with the average number of alleles A = 7.86, the number of effective alleles Ae = 3.90, the average expected heterozygosity He = 0.69, the observed heterozygosity H0 = 0.37. According to the results of genetic structure analysis, the fixed index (F) was 0.25 ~ 0.79, indicating that maize landraces are typical mixed breeding systems. Due to the lack of hybrids, the genetic structure of maize landraces and groups deviated from Hardy-Weinberg equilibrium . The average ratio of heterozygous genes (Fst) was 0.07, indicating that the genetic variation within and among cultivars accounted for 7% and 93% of the total genetic variation, respectively. The genetic diversity within maize landraces and genetic distance analysis showed that the maize landraces distributed in Sichuan have the most abundant genetic variation in southwest China. According to the comprehensive analysis, it is speculated that the earliest cultivars of maize in Southwest China were introduced to Sichuan and spread to adjacent areas.