Species and Distribution of Fusarium Causing Ginseng Root Rot and Antifungal Efficacy of Captan and Hymexazol against F. spp. in China

Fusarium root rot on ginseng (FRRG) is an important root disease that seriously affects ginseng (Panax ginseng) yield and quality. However, the species categories and distribution of Fusarium causing ginseng root rot in China have not been systematically examined. A total of 571 pure Fusarium isolates were obtained from 2018 to 2019 from 14 ginseng-producing regions in Jilin, Liaoning, and Heilongjiang Provinces, China. Based on multi-locus sequence analysis of ITS-tef1-rpb2 and morphological characteristics, 571 Fusarium isolates were identified as F. oxysporum (accounting for 47.46% of the total isolates), F. solani (35.38%), F. equiseti (5.78%), F. proliferatum (2.80%), F. cerealis (1.75%), F. semitectum (1.75%), F. acuminatum (1.75%), F. redolens (1.58%), F. verticillioides (1.05%), and F. graminearum (0.70%). Among them, F. oxysporum and F. solani were the dominant species, and F. graminearum and F. verticillioides were first recorded on ginseng in China. The fungicides captan and hymexazol were tested in vitro for their inhibitory activities against ten Fusarium species. All Fusarium species displayed enhanced sensitivity to captan compared with hymexazol. The protective effects of captan against ginseng root rot caused by F. oxysporum (FoRRG) ranged from 94.07% to 97.78% at concentrations of 200, 400, and 600 µg·mL−1; however, its curative effects were much lower, ranging from 29.63% to 35.56%. In comparison, hymexazol exhibited protective effects of only 24.00% to 52.00% and curative effects of 16.00% to 45.33% at concentrations of 600 to 1000 µg·mL−1. In addition, microconidia were highly sensitive to both fungicides, compared with mycelia and macroconidia.