我国热带作物多主棒孢种群多样性及致病力分化分析

多主棒孢（Corynespora cassiicola）是一种全球分布的重要植物病原真菌,寄主范围十分广泛。近年来,该病原菌侵染危害多种热带作物,并在局部地区大面积暴发流行,造成巨大的经济损失。本研究利用核糖体转录间隔区（Internal transcribed spacer, ITS）、翻译延伸因子（translation elongation factor 1 alpha, EF-1α）、β微管蛋白（β-Tubulin, TUB）,对来自橡胶树、木薯、番木瓜和瓜菜等多种热带作物的70株多主棒孢进行种群多样性分析。结果发现,利用最大似然法,在相似系数为0.97时可将供试菌株划分为两大遗传类群：类群Ⅰ为国内和一些国外橡胶树的多主棒孢;类群Ⅱ为其他寄主多主棒孢,遗传类群与寄主来源具有显著的相关性。致病力测定表明,多主棒孢种内致病力分化明显,类群Ⅰ的橡胶树多主棒孢仅能侵染橡胶树,不能侵染其他寄主,具有明显的寄主专化性,且不同地理来源的菌株致病力差异不显著。类群Ⅱ的多主棒孢在不同寄主间可以相互侵染,但菌株在致病力和发病症状上存在一定差异,表现出对其原寄主的高度致病力。多基因序列聚类分析与致病力分化分析结果具有较好的一致性,这为研究我国热带作物多主棒孢的种群结构、主要致病型以及为多主棒孢病害的发生、流行和防治提供了理论依据。

Genetic Diversity and Pathogenic Variability Among Isolates of Corynespora cassiicola from Tropical Crops in China

Corynespora cassiicola is an important plant pathogenic fungus distributed globally and has a wide host range. In recent years, C. cassiicola had infected a variety of tropical crops. The diseases caused by C. cassiicola has outbroken in some areas, causing huge economic losses. In this study, we used ITS, EF-1α and β-tubulin genes to analyze the population diversity of isolates of C. cassiicola collected from rubber trees, cassava, papaya, tropical fruits and vegetables. When the similarity coefficient was 0.97, the tested isolate could be divided into two divergent clusters by the maximum likelihood method. Cluster I was the isolates of rubber trees, which came from China and some foreign countries, and cluster II was the isolates of other hosts. There was significant correlation between genetic clusters and host source. Pathogenicity test showed that the pathogenic differentiation of C. cassiicola was obvious. The isolates of cluster I could only infect rubber trees, but could not infect other hosts. They had obvious host specificity, and there was no significant difference in pathogenicity among isolates from different geographical sources. C. cassiicola in cluster II could infect each other among different hosts, but the pathogenicity and symptoms of the isolates were different, showing a high pathogenicity to the original hosts. The results of genetic diversity and pathogenic variability showed a good consistency, which would provide a theoretical basis for understanding the population structure and main pathogenic types among the isolates of C. cassiicola from tropical crops in China, as well as the occurrence, epidemic and control method of the diseases caused by C. cassiicola.