Curvularia lingshanensis sp. nov., a New Pathogen Causing stem and leaf rot on Curcuma kwangsiensis and Its Sensitivity to Five Fungicides

Abstract

Curcuma kwangsiensis S. G. Lee et C. F. Liang (Zingiberaceae) is a traditional Chinese medicinal plant that is cultivated in the South-West of China. In this study, five fungal strains were isolated from diseased C. kwangsiensis plants in Lingshan County, Guangxi Province. The phylogenetic analyses, based on a combined dataset of ITS, GAPDH, and EF-1α gene sequences, revealed that the strains from this study formed a distinct clade separate from other known Curvularia species. Additionally, these strains were closely related to C. tamilnaduensis, C. radici-foliigena, and C. radicicola. Based on morphological observations, the strains exhibit distinct variations in conidiophore length, conidiogenous cell characteristics, as well as conidial size and shape, distinguishing them from similar species. Consequently, these five strains have been classified as a novel species, C. lingshanensis. Pathogenicity test carried out on the plants confirmed that the new species was pathogenic to C. kwangsiensis. Five fungicides were tested for their toxicity to the pathogen using the mycelial growth rate method. Results indicated that among the studied fungicides, 70% mancozeb, 10% difeno-conazole and 75% trifloxystrobin·tebuconazole had the highest antifungal activity against C. lingshanensis with EC50 values of 1.5233 ± 0.18 mg/L, 0.1748 ± 0.03 mg/L, 0.2557 ± 0.06 mg/L, respectively. This study provides the first report of a severe stem and leaf rot disease on C. kwangsiensis caused by C. lingshanensis and important guidance for preventing and controlling this disease effectively.