四川省稻瘟病菌群体遗传结构分析

Genetic Structure of Rice Blast Pathogen Magnaporthe oryzae in Sichuan Province

由稻瘟病菌（Magnaporthe oryzae ）侵染引起的稻瘟病是全球水稻生产上最严重的病害之一.利用6对 SSR 荧光标记对采自四川绵阳、营山、雅安、北川和武胜地区的5个稻瘟病菌群体的遗传结构进行分析.结果表明,在124个稻瘟病菌中检测出43个等位基因,平均每个位点的观测等位基因数为7．2,有效等位基因数为3．1,所有位点均显著偏离 Hardy-Weinberg平衡.5个群体的平均观测杂合度（0．374）低于期望杂合度（0．502）,暗示群体内存在因近交而导致的杂合子缺失. AMOVA 分析显示,绝大多数遗传变异（81．17％）存在于群体内个体间,仅有18．83％的变异来自于群体间的差异.5个地理群体间呈现高水平的遗传分化（遗传分化系数为0．057~0．528）.Mantel 检验表明,群体间的遗传距离与地理距离相关未达显著水平,说明稻瘟病菌的遗传变异呈现随机分布的空间模式.群体遗传学数据分析表明5个群体间存在不同程度的基因流（基因流水平为0．472~4．347）,基于贝叶斯聚类法的 Structure 分析也证实了这一结果.

Rice blast,caused by Magnaporthe oryzae ,is one of the most destructive disease worldwide.The genetic structure of five populations of M .oryzae ,collected from Mianyang,Yingshan,Ya’an,Beichuan and Wusheng of Sichuan Province,were analyzed using six fluorescent labeled SSR markers.A total of 43 polymorphic alleles were produced in 124 isolates of M .oryzae .The mean number of observed alleles （Na ）and effective alleles （Ne ）per locus were 7.2 and 3.1 ,respectively,and all loci exhibited significant deviations from Hardy-Weinberg equilibrium.The mean observed heterozygosity （Ho = 0.374 ）was lower than expected （He = 0.502 ）,indicating the deficit of heterozygotes resulting from the accumulation of inbreeding within populations.Analysis of molecular variance showed that the majority （81 .1 7%）of genetic variation was attributed to the differences among isolates within population,with only 18.83% of the variation resulting from differences among populations.High levels of genetic differentiation （Fst , 0.057-0.528）existed among all five geographical populations.Mantel test revealed no significant correlation between the genetic and geographical distances for all populations （r = - 0.201 ,P = 0.587 ）,indicating that the genetic variation of M .oryzae populations was randomly distributed in geographic space.Different levels of gene flow （Nm , 0.472 - 4.347）,occurred between populations,were also verified by Bayesian-based clustering algorithm analysis by Structure.