Characterization and fungicide sensitivity of Colletotrichum godetiae causing sweet cherry fruit anthracnose in Guizhou, China

Abstract

Sweet cherry is an important fruit crop with high economic and ornamental value in China. However, cherry fruit anthracnose, caused by Colletotrichum species, greatly impacts cherry yield and quality. Here, we surveyed cherry anthracnose in Guizhou, China from 2019-2020. Necrotic sweet cherry fruits were collected from different areas in Guizhou and examined. A total of 116 Colletotrichum strains were isolated from these symptomatic fruits. Based on the morphological characteristics of the isolates and phylogenetic analyses of concatenate internal transcribed spacer (ITS) region and ACT, CHS-1, GAPDH, TUB2, and HIS3 genes, the pathogen responsible for causing sweet cherry anthracnose was identified as Colletotrichum godetiae. Pathogenicity tests were conducted by inoculating healthy sweet cherry fruits with spore suspensions of the fungal pathogen, and Koch's postulates were confirmed by pathogen re-isolation and identification. The Q-1 isolate showed different sensitivities to 13 fungicides, exhibiting seven different modes of action, and its EC₅₀ values ranged from 0.04 to 91.26 μg ml^-1. According to that, the sensitivity of 20 isolates from different samples to ten fungicides with better performance, were measured. The results showed that 6 of the 10 fungicides (difenoconazole, propiconazole, prochloraz-manganese, pyraclostrobin, trifloxystrobin-tebuconazole, and difenoconazole-azoxystrobin) all showed higher sensitive to the 20\u00B0C. godetiae isolates, and no resistance groups appeared. Its EC50 values ranged from 0.013 to 1.563 μg ml^-1. In summary, this is the first report demonstrating that C. godetiae causes sweet cherry anthracnose and the results of this study provide insights into how sweet cherry anthracnose could be effectively controlled in China.

Keywords: Cerasus pseudocerasus; Colletotrichum; multi-gene; plant disease; sweet cherry fruit anthracnose.

Figure 1

Distribution of cherry sample sites in four regions in Guizhou, China.

Figure 2

The symptoms of cherry anthracnose on fruits. (A) Symptoms on fruits in field. (B) Symptoms on fruits at different development stages. (C) Necrotic spot on mature fruit. (D) Margin of lesions on mature fruit.

Figure 3

Morphological characteristics of Colletotrichum godetiae were observed on the diseased fruits. (A) Acervuli, bar = 50 μm. (B) Setae, bar = 20 μm. (C–F) Conidiophores, bar = 10 μm. (G) Conidia, bar = 10 μm.

Figure 4

Morphological characteristics of Colletotrichum godetiae cultured on PDA plates. (A,B) Colony morphology on upside (A) and underside (B) of C. godetiae on PDA after 7 days at 25°C. (C) Setae, bar = 20 μm. (D) Mycelial appressorium, bar = 10 μm. (E) Conidiophores, bar = 10 μm. (F) Conidia, bar = 10 μm. (G,H) Appressorium, bar = 10 μm.

Figure 5

Maximum-likelihood (ML) and Bayesian inference (BI) phylogenetic tree illustrating the relationships with the godetiae species complex and the Colletotrichum strains isolated from diseased cherry fruits in Guizhou. Bootstrap support values for ML greater than 50% and Bayesian posterior probabilities greater than 0.90 are shown next to topological nodes.

Figure 6

Pathogenicity test of Colletotrichum godetiae isolates obtained from Qianxinanzhou. (A) CK was treated with sterilized distilled water. (B–D) Lesions on cherry fruits were inoculated with Q-1, Q-2 and Q-3 isolates, respectively.