Species and Distribution of <i>Fusarium</i> Causing Ginseng Root Rot and Antifungal Efficacy of Captan and Hymexazol Against <i>Fusarium</i> spp. in China

Fusarium root rot on ginseng is an important root disease that seriously affects ginseng (<i>Panax ginseng</i>) yield and quality. However, the species categories and distribution of <i>Fusarium</i> causing ginseng root rot in China have not been systematically examined. A total of 571 pure <i>Fusarium</i> isolates were obtained from 2018 to 2019 from 14 ginseng-producing regions in Jilin, Liaoning, and Heilongjiang provinces, China. Based on multilocus sequence analysis of ITS-<i>tef1</i>-<i>rpb2</i> and morphological characteristics, the 571 <i>Fusarium</i> isolates were identified as <i>F</i>. <i>oxysporum</i> (accounting for 47.46% of the total isolates), <i>F</i>. <i>solani</i> (35.38%), <i>F</i>. <i>equiseti</i> (5.78%), <i>F</i>. <i>proliferatum</i> (2.80%), <i>F</i>. <i>cerealis</i> (1.75%), <i>F</i>. <i>semitectum</i> (1.75%), <i>F</i>. <i>acuminatum</i> (1.75%), <i>F</i>. <i>redolens</i> (1.58%), <i>F</i>. <i>verticillioides</i> (1.05%), and <i>F</i>. <i>graminearum</i> (0.70%). Among them, <i>F</i>. <i>oxysporum</i> and <i>F</i>. <i>solani</i> were the dominant species, and <i>F</i>. <i>graminearum</i> and <i>F</i>. <i>verticillioides</i> were first recorded on ginseng in China. The fungicides captan and hymexazol were tested in vitro for their inhibitory activities against 10 <i>Fusarium</i> species. All <i>Fusarium</i> species displayed enhanced sensitivity to captan compared with hymexazol. The protective effects of captan against ginseng root rot caused by <i>F</i>. <i>oxysporum</i> 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 1,000 μg·ml^-1. In addition, microconidia were highly sensitive to both fungicides, compared with mycelia and macroconidia.