Molecular Characterization and Fungicide Sensitivity of Jujube Pathogens Colletotrichum gloeosporioides Sensu Stricto and Colletotrichum nymphaeae in South Korea

Jujube (Ziziphus jujuba) is cultivated across South Korea because of its medicinal and economic value. It is used as a sweetener in jam, tea, and snacks and a garnish in many cuisines. Anthracnose caused by Colletotrichum spp. accounts for huge economic losses for jujube growers. In 2019 and 2020, severe anthracnose was observed in the jujube-growing areas of South Korea. The infected fruit displayed small, water-soaked, sunken, circular spots. Infected fruit were collected from different commercial orchards of Boeungun and Gyeongsan regions of South Korea, and putative causal agents were isolated on potato dextrose agar. Based on the morphological and molecular characteristics, the fungal isolates were identified as Colletotrichum gloeosporioides sensu stricto and C. nymphaeae. The pathogenicity of these isolates was confirmed by inoculating a conidial suspension (1 × 106 conidia ml-1) on healthy fruit. The in vitro sensitivity of the fungal isolates to tebuconazole, carbendazim, and azoxystrobin was also tested. All isolates showed high sensitivity to azoxystrobin in terms of mycelial growth inhibition (half maximal effective concentration value of 0.01 to 0.6 μg/ml). To the best of our knowledge, this is also the first report of jujube anthracnose caused by C. nymphaeae in South Korea.