稻瘟病菌群体的分子遗传学研究III.——广东省2001年度稻瘟病菌群体的遗传结构分析以及两个假说的提出

MOLECULAR GENETIC STUDIES ON THE RICE BLAST FUNGUS POPULATION III. GENETIC STRUCTURE OF THE FUNGUS POPULATION IN 2001 IN CHINESE GUANGDONG AND TWO HYPOTHESES PROPOSED PAN

利用随机扩增多态性DNA技术(randomamplifiedpolymorphicDNA,RAPD)对广东省2001年度稻瘟病菌群体的遗传结构进行了分析。以相似性系数为0.70阈值时,可将采集于广东省三大生态稻作区、早稻和晚稻生长季节的96个菌株划分为12个遗传宗谱;其中宗谱8和9的菌株数各占总数的25%和18.8%,为优势宗谱。从稻作区来看,宗谱3和8为各个稻作区的共同宗谱;而宗谱1和2,7和11,以及9、10和12则依次是粤北、粤中和粤南稻作区的特异性宗谱。从生长季节来看,来源于早、晚季的菌株完全分属于宗谱图的上、下两个半区,彼此之间不存在共同的宗谱;而且两个优势宗谱都集中于晚季供试亚群体。结合前两次实验的结果,作者提出了如下两个假说来解释广东省稻瘟病菌群体所表现的遗传特性:一个地区或生长季节的病原菌群体,其优势宗谱所占的比例越高,该地区或生长季节病害发生就越严重;在长期的水稻栽培历史中,稻瘟病菌群体可能逐步地形成了早季宗谱(小种)和晚季宗谱(小种)的遗传分化。如何进一步验证上述两个假说是值得我们进一步探讨的重要课题。

Genetic structure of the rice blast fungus population in 2001 in Guangdong Province (GD), China was assessed through RAPD (random amplified polymorphic DNA) approach. 96 isolates collected from three rice-growing regions in early and late seasons in 2001 were divided into 12 genetic lineages drew by unweighted pair group method using arithmetic average (UPGMA) at the similarity coefficient of 0.70. Among the 12 genetic lineages, lineages 8 and 9, which consisted of 24 and 18 isolates, respectively, were recognized as dominant lineages in 2001; lineages 3 and 8 were the common ones to three regions; and lineages 1 and 2, 7 and 11, and 9, 10 and 12 were recognized as region-specialized lineages responsible to North, Middle, and South GD, respectively. As to the rice-growing seasons, there is not any common lineage for the two seasons, and both dominant lineages were filled in the late season group. Taken together, more than 300 isolates tested, which were selected from 1998 to 2001 in GD, two hypotheses in regard to the temporal and spatial characters of the rice blast fungus population in GD were proposed: the proportion of dominant lineage in a population in a region or season may be positively relative to the incidence of the blast; and the rice blast fungus population may has been differentiated into the early and late lineages and/or races in GD.