Identification of fungal pathogen causing charcoal rot disease of Mung Bean and infection to economically important plants

Abstract

Charcoal rot disease affects to mung bean product and quality in Thailand. The fungal pathogen infects mung bean all growth stages from seedling to harvesting. Moreover, it can survive in the soil for a long period of time. The aims of this research were to identify the fungal pathogen causing charcoal rot of mung bean and to investigate aggressiveness on other economically important plants. Twenty-six isolates of the pathogen collected from 6 areas in Chai Nat, Uthai Thani, Nakhon Sawan, Lopburi, Phetchabun and Nan provinces. Morphological and colony characteristics were investigated, then all isolates were grouped into 5 groups. Representative isolates of each group were considered using molecular technique. Identification was based on sequencing of ITS region (ITS1-5.8s-ITS2) and TEF1-alpha contained sequences approximately 800 and 900 bp, respectively, then identified as Macrophomina phaseolina. Pathogenicity test on 5 different economically plant crops such as mungbean cv. Chai Nat 72, peanuts cv. Thainan, cowpea black grain cv. Ubon Ratchathani, waxy corn cv. Big white 852 F1 and black sesame cv. Ubon Ratchathani 3 were examined using unwounded inoculation by M. phaseolina NAN203 on seed coat and root. Diseased symptoms occurred on all crops, similarly.  Stem and root lesions first appeared water soaked but then turn a dull light brown with senesced leaves still attached to the plants, later turn to be dark brown necrotic symptom. The infected plants wilted and the fungus rapidly colonized the remaining tissues. The dead tissues turned black as microsclerotia were abundantly produced. This research indicated aggressiveness of the single fungus, M. phaseolina which can infect various hosts, it is very crucial to develop disease management program in the field, absolutely.