Abstract:

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.

Key words: tropical crops, Corynespora cassiicola, population diversity, pathogenic variability