First report of Colletotrichum fructicola causing anthracnose on Arachis hypogaea in Brazil

Peanut (Arachis hypogaea) is an economically important crop, with global production exceeding 54 million tons annually (FAOSTAT 2023). In March 2024, a leaf spot disease was observed on leaves of peanut plants in three commercial crop areas in Conceição do Araguaia, Pará State, northern Brazil (8°30'23"S, 49°28'52"W; 8°27'28"S, 49°28'50"W; and 8°27'43"S, 49°28'51"W). Initially, the lesions were dark, necrotic, and rounded in shape. As the disease progressed, the dark necrotic lesions coalesced and formed irregular large spots which leading to the defoliation. Approximately 75% of plants across the surveyed areas showed symptoms. Ten diseased plants were collected from each sampled area, resulting in a total of 30 plants analyzed. The leaf tissues from the diseased plants were surface-sterilized (50% alcohol for 30s followed by 1% NaClO for 40s; three rinses with sterile distilled water). They were then placed on potato dextrose agar and incubated at 25°C under a 12-hour photoperiod for 14 days. Five Colletotrichum-like isolates (AM11, AM12, AM13, AM14, and AM15) were obtained. The isolates presented whitish to grey colonies with a dark-grey reverse. The conidia were hyaline, aseptate, cylindrical with obtuse ends, measuring 12–15 × 4.5–5.5 μm (n = 50). Appressoria were ovoid to irregular, measuring 8.4–11 × 5.3–6.8 μm (n = 50), matching the descriptions of Colletotrichum fructicola (Cannon et al. 2012). PCR amplification and sequencing of the glyceraldehyde-3-phosphate dehydrogenase (GAPDH), intergenic spacer between DNA lyase and mating-type locus MAT1-2-1 (APN2/MAT-IGS), glutamine synthetase (GS), and β-tubulin (TUB2) genes were performed (GenBank accession numbers: for GAPDH: PX597398, PZ404928, PZ404929, PZ404930 and PZ404931; for APN2/MAT-IGS: PX597399, PZ404932, PZ404933, PZ404934 and PZ404935; for GS: PX597397, PZ404936, PZ404937, PZ404938 and PZ404939; for TUB2: PX597396, PZ404940, PZ404941, PZ404942 and PZ404943). BLASTn searches showed 98% to 100% identities with Colletotrichum fructicola CBS125397, the ex-type strain of C. fructicola. A maximum likelihood multilocus phylogenetic analysis based on GAPDH, APN2/MAT-IGS, GS, and TUB2 sequences, including reference CBS strains, was performed using the GTR-GAMMA model with 1000 bootstrap pseudoreplicates. Our isolates grouped within the Colletotrichum fructicola clade with 99% bootstrap support, confirming their identity as C. fructicola. For the pathogenicity test, a total of ten peanut plants of the Tatu-Vermelho cultivar, 60 days old, were used. For each isolate, two plants were inoculated by spraying with conidial suspensions (2 × 10⁶ conidia/mL). Subsequently, they were kept in a humid chamber for 48 hours before being transferred to a greenhouse, under a temperature of 28°C and 85% relative humidity. Sterile distilled water was sprayed onto the peanut plants and used as a control. Necrotic lesions developed three days after inoculation, whereas control plants remained asymptomatic. The pathogen was reisolated from symptomatic tissues, fulfilling Koch’s postulates. Colletotrichum mangenoti, C. dematium, C. arachidis, C. truncatum, C. chlorophyti, C. curvatum, C. gloeosporioides and C. capsici have been reported on peanut worldwide (Resplandy et al. 1954; Shivas 1989 and Li et al. 2024). Colletotrichum fructicola was recently reported causing peanut anthracnose in China (Gong et al. 2023; Li et al. 2024), but no record exists for Brazil. To our knowledge, this is the first report of Colletotrichum fructicola causing anthracnose on Arachis hypogaea in Brazil. This finding expands the known host range of C. fructicola in South America and highlights the need to re-evaluate historical records of C. gloeosporioides sensu lato associated with peanuts.