用SSR标记分析1949—2005年华南地区常规籼稻主栽品种遗传多样性及变化趋势

利用均匀分布于水稻基因组的300个SSR标记对95个华南地区不同年代常规籼稻主栽品种进行分析,研究该地区常规稻品种的遗传多样性及其变化趋势。检测到236个SSR标记有多态性,共获得776个等位基因,每个位点等位基因2~12个,平均3.29个,共有206个位点的等位基因数介于2~4个,占全部多态性位点的87.3%。多态性标记位点的PIC值平均为0.42,变化范围为0.041~0.790。不同染色体的位点多态性差异显著,其中第10染色体的位点平均等位基因数最多,PIC值最高,而第5染色体的位点平均等位基因数最少,PIC值最低;6个年代中,50~70年代育成品种包含等位基因数呈显著的上升趋势,70年代达最高值2.83,随后逐渐下降。分子方差分析(AMOVA)结果显示不同年代间遗传变异仅占总体变异的3.77%,但仍达极显著水平(P0.001)。不同年代育成品种的遗传距离(GD)呈下降趋势。聚类分析结果显示,在遗传相似系数(GS)为0.685处可将品种区分为5大类,表明华南地区各时期的常规稻品种遗传改良都是围绕少数骨干亲本进行的。试验结果显示,华南地区籼稻品种的遗传多样性狭窄且随年代而变化,70年代以后呈下降趋势,在今后的育种中应扩大亲本选材范围、拓宽育种亲本的遗传基础以提高育成品种的遗传多样性。

SSR Analysis of Genetic Diversity and the Temporal Trends of Major Commercial Inbred Indica Rice Cultivars in South China in 1949-2005

Three hundred SSR makers distributing evenly on the whole rice genome wereused to assess the genetic diversity among 95 major commercial inbred indica rice cultivars in South China in 1949–2005. Of the 300 SSR loci, 236 loci were polymorphic. A total of 776 alleles were detected at the 236 polymorphic loci. The mean number of alleles per locus was 3.29 with a range from 2 to 12. Two hundred and six SSR loci with 2 to 4 alleles accounted for 87.3% of all the 236 polymorphic loci. The average polymorphism information content (PIC) value was 0.42 with a range from 0.041 to 0.790. Among the 12 chromosomes, chromosome 10 showed the greatest values in mean allele number and PIC value, but chromosome 5 showed the lowest values. In six investigated decades, the number of detected alleles per locus increased from 1950s to 1970s, and then decreased after 1970s. Analysis of molecular variance (AMOVA) indicated that the genetic variation among the six decades was significant (P＜0.001)，though it just accounted for 3.77% of the total genetic variation. Genetic distance (GD) among cultivars gradually decreased from 1950s to 2000s. Clustering analysis with COMPLETE method based on genetic similarity coefficients (GS) showed that all the cultivars could be separated into five clusters with GS value 0.685. The clustering result indicated that the genetic improvement of inbred rice cultivars was just based on several core parents in different decades. It could be concluded that the genetic diversity of indica rice cultivars in South China is narrow and has been decreasing after 1970s, therefore there’s a need for incorporating new variability into the existent rice germplasm for broadening the genetic basis of cultivars.