First Report of Colletotrichum theobromicola Causing Anthracnose Leaf and Twig Spot in Cambuci (Campomanesia phaea) in Brazil

Cambuci (Campomanesia phaea [O. Berg.] Landrum) is an endemic fruit tree of the Atlantic forest belonging to the family Myrtaceae. In Brazil, the enormous economic potential of cambuci fruit for small farms has encouraged its cultivation, contributing for the biome preservation. In April 2016, reddish-brown, circular to irregular spots on leaves and young branches occurred on 100% of the plants growing in a nursery in Piracicaba, São Paulo State, Brazil. Initial lesions measured 1 to 5 mm and gradually evolved into larger coalescing lesions with acervuli showing black setae. Small pieces (2 mm) from the periphery of the lesion tissue collected from diseased leaves and twigs were surface disinfested (1 min in 70% alcohol, 2 min in 1% NaOCl, and rinsed with sterile water), plated on water agar (WA) medium, and incubated at 25°C for 7 days. Ten single conidial isolates morphologically identical were obtained, cultivated, and two isolates were selected for characterization (Col1USP and Col2USP). Isolates were stored in the mycological collection of the Laboratory of Epidemiology of the University of São Paulo. Colonies were grayish-white when incubated on potato dextrose agar (PDA) at 25°C with a 12-h photoperiod for 6 days. Conidia obtained on synthetic nutrient-poor agar (SNA) medium were subcylindrical with rounded ends, straight, hyaline, aseptate, 10.8 to 18.1 µm long and 3.4 to 4.7 µm wide (n = 60). DNA was obtained using a Promega Wizard genomic DNA purification kit (Madison, WI). For accurate identification, partial sequences of actin (ACT), glutamine synthetase (GS), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), internal transcribed spacer (ITS), and β-tubulin 2 (β-TUB) (Weir et al. 2012) were generated and deposited in GenBank (accession nos. KX721061 to KX721070). BLAST queries of the sequences shared 99 to 100% identity with Colletotrichum theobromicola. Additionally, maximum parsimony analysis using multilocus alignment (ACT, GS, GAPDH, ITS, and β-TUB) placed the two isolates in the same clade with other C. theobromicola isolates. For pathogenicity test, 1-year-old cambuci plants, originated from seeds collected in wild plants, without any anthracnose symptoms, were sprayed with conidial suspension (106 conidia ml–1). Five single-cambuci replicates were used for each isolate. The plants were covered with plastic bags for 48 h and kept at 25°C on the laboratory bench for 3 weeks. Five additional cambuci plants were mock-inoculated with sterile water. After 7 days, all C. theobromicola-inoculated plants showed reddish-brown spots on leaves and twigs. The isolates were reisolated from the lesions, fulfilling Koch’s postulates. No symptoms were observed on mock-inoculated plants. Pathogenicity test was performed twice. The genus Colletotrichum is known to cause anthracnose in different crops causing serious economic losses (Cannon et al. 2012). In Brazil, C. theobromicola was reported on eucalyptus (Rodrigues et al. 2014) and barbados cherry (Bragança et al. 2014). To our knowledge, this is the first report of C. theobromicola causing anthracnose leaf and twig spot in cambuci. © The American Phytopathological Society.