First Report of Colletotrichum fructicola Causing Anthracnose in Cassava (Manihot esculenta) in Brazil

Cassava is a staple food for African, Latin American, and Asian countries, and is also raw material for starch and ethanol (Pinweha et al. 2015). Anthracnose is one of the most important diseases causing plant death. In May 2014, necrotic and irregular shaped spots and sunken lesions on fruits and stems were observed on plants in a commercial field from the Aliança Cooperativa do Amido-COOPAMIDO (located at Laje, Bahia, Brazil, 13°6′34.7″ S; 39°16′42.4″ W). Fifteen isolates were obtained, and 2 strains (PPAM10 and PPAM13) were used for characterization. The isolates grew on potato dextrose agar (PDA) and synthetic nutrient-poor agar (SNA) medium at 25°C and a 12-h photoperiod. On PDA, the colonies were white to gray on the upper surface and orange to gray on the reverse side, after 7 days. On SNA, the conidia were cylindrical to subcylindrical, hyaline and guttulate, with 16.7 to 23.3 (avg. 20) × 5.1 to 7.5 (avg. 6.2) µm (n = 50). Conidia length/width ratio was 2.5 to 4.1. The sexual stage was more frequently observed than the asexual stage, and the ascospores had tapering ends, were slightly curved, hyaline and 15.8 to 16.2 (avg. 19.7) × 4.4 to 8.6 (avg. 6.2) µm (n = 50). Pathogenicity was confirmed in cassava plants under greenhouse conditions, and detached cassava leaves. The inoculation in cassava stems and leaves was carried out by depositing a 5-mm plug of PDA containing sporulating colonies on the tissue wounded with a sterilized needle and on nonwounded stems and leaves, with 10 replicates per treatment. Both were incubated in a moist chamber at 25°C and symptoms appeared after 3 days. No symptoms were observed on stems and leaves inoculated with a sterile PDA plug. The isolate recovered from the inoculated tissues showed the same morphological characteristics as those of the isolate used in inoculations. The fungal DNA was extracted by CTAB protocol (Murray and Thompson 1980); partial sequences of GAPDH, CHS-1, and CAL genes (Weir et al. 2012) were generated, used in a BLAST search in GenBank, and were 99 to 100% similar to Colletotrichum fructicola. Phylogenetic studies were conducted based on neighbor-joining analysis and Bayesian inference for the genes alone, and concatenated. The sequences for the PPAM10 were: CAL (KP763675), CHS (KP763682), and GAPDH (KP763689), and matched with strains UASB-Cg-46 (CAL, KC790926), C1216.5 (CHS, JX009762), and ITCC6270 (GAPDH, KC790774) with 100% similarity, respectively. The sequences from PPAM 13 (CAL, KP763676, and GAPDH, KP763690) matched with strain ICMP:17789 (CAL, JX009665) and PGYLQ2-1 (GAPDH, KF791586) with 100% and 99% similarity, respectively. The sequences were also compared with ex-type cultures of C. fructicola (CBS 125397 and CBS 238.49) and the identities of the PPAM10 were 100% for CAL (JX009674 and JX009671) and GAPDH (JX010032 and JX009923), and for PPAM13 the identities were 99% for both genes of the same ex-type cultures (CBS 125397 and CBS 238.49). PPAM10 and PPAM13 belong to distinct subgroups within C. fructicola clade, C. ignotum and Glomerella cingulata var. minor, respectively. Colletotrichum fructicola was originally described on coffee berries (Prihastuti et al. 2009) and C. ignotum on cacao (Rojas et al. 2010); in a recent study, both species together with the teleomorphic G. cingulata var. minor were recognized as synonyms of C. fructicola (Weir et al. 2012). To our knowledge, this is the first report of C. fructicola causing anthracnose in cassava. © 2016, American Phytopathological Society. All rights reserved.