Identification and Pathogenicity of Globisporangium sp. Isolates Causing Tomato Stem Rot in Korea

In March 2020, unfamiliar stem rot symptoms were found in tomato (Solanum lycopersicum) plants grown for 40-50 days in trays in a greenhouse located in Pyeongchang, Korea. The symptoms initially developed on the basal stems and later extended up the stems above the soil line. The disease incidence on the tomato plants in the trays in the greenhouse ranged from 5% to 10%. Four fungal isolates were obtained from the diseased stems and identified as Globisporangium sp. based on their morphological characteristics. Phylogenetic analysis of the isolates revealed that the isolates were divided into two groups. Among the four isolates of Globisporangium sp., one clustered with Globisporangium irregulare, and the others clustered with each other but not with any reference Globisporangium species. It is suggested that the three isolates are likely to be a novel species. The isolates of G. irregulare and Globisporangium sp. were tested for their pathogenicity on tomato stems through artificial inoculation. Both the Globisporangium spp. isolates caused stem rot symptoms similar to those observed in the investigated greenhouse. This is the first report of G. irregulare and Globisporangium sp. causing tomato stem rot in Korea.