Colletotrichum and Diaporthe species associated with soybean stem diseases in Myanmar

In 2017, premature abscission of leaves and dry rot with discoloration on the epidermis of the stem were observed in the field of reproductive-stage soybean in southern Shan State and the Nay Pyi Taw region in Myanmar. On the basis of morphological characteristics, two fungal genera, Colletotrichum and Diaporthe, were identified. Multilocus phylogenetic analyses based on the ITS, TUB and EF1-α genes for Diaporthe and the ITS, ACT, GAPDH, and CHS-1 genes for Colletotrichum were used to identify the species as Colletotrichum plurivorum, C. truncatum, Diaporthe endophytica and D. melonis. The pathogenicity of the collected isolates was confirmed by inoculation of soybean cultivar (Yezin-10), and all species except for C. plurivorum were virulent. The isolates of C. plurivorum were less aggressive than the other isolates. Koch’s postulate was fulfilled by reisolation of the original inoculated fungal isolates from the symptomatic tissue. In two locations in Myanmar, C. plurivorum, D. endophytica and D. melonis occurred in southern Shan State, whereas only one C. truncatum was found in the Nay Pyi Taw region. This is the first report of Colletotrichum and Diaporthe species associated with soybean stem diseases in Myanmar.