First Report of Colletotrichum gloeosporioides Causing Anthracnose on Frafra Potato (Coleus rotundifolius) in Ghana

Abstract

HomePlant DiseaseVol. 106, No. 10First Report of Colletotrichum gloeosporioides Causing Anthracnose on Frafra Potato (Coleus rotundifolius) in Ghana PreviousNext DISEASE NOTE OPENOpen Access licenseFirst Report of Colletotrichum gloeosporioides Causing Anthracnose on Frafra Potato (Coleus rotundifolius) in GhanaB. A. Okorley, J. N. Amissah, S. T. Nyaku, F. Kusi, A. Danquah, and E. Y. DanquahB. A. Okorleyhttps://orcid.org/0000-0002-4433-8471Crop Science Department, University of Ghana, Legon Accra, GhanaSearch for more papers by this author, J. N. Amissah†Corresponding author: J. N. Amissah; E-mail Address: [email protected]https://orcid.org/0000-0003-4520-4958Crop Science Department, University of Ghana, Legon Accra, GhanaSearch for more papers by this author, S. T. NyakuCrop Science Department, University of Ghana, Legon Accra, GhanaSearch for more papers by this author, F. KusiCouncil for Scientific and Industrial Research (CSIR), Savannah Agricultural Research Institute, Manga, Upper East Region, GhanaSearch for more papers by this author, A. Danquahhttps://orcid.org/0000-0003-3840-3799West Africa Centre for Crop Improvement (WACCI), University of Ghana, Legon Accra, GhanaSearch for more papers by this author, and E. Y. DanquahWest Africa Centre for Crop Improvement (WACCI), University of Ghana, Legon Accra, GhanaSearch for more papers by this authorAffiliationsAuthors and Affiliations B. A. Okorley1 J. N. Amissah1 † S. T. Nyaku1 F. Kusi2 A. Danquah3 E. Y. Danquah3 1Crop Science Department, University of Ghana, Legon Accra, Ghana 2Council for Scientific and Industrial Research (CSIR), Savannah Agricultural Research Institute, Manga, Upper East Region, Ghana 3West Africa Centre for Crop Improvement (WACCI), University of Ghana, Legon Accra, Ghana Published Online:16 Aug 2022https://doi.org/10.1094/PDIS-01-22-0229-PDNAboutSectionsView articlePDFSupplemental ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat View articleFrafra potato (FP) (Coleus rotundifolius [Poir.] A. Chev. & Perrot) is a tuber crop with great potential to improve food security in Ghana. In July 2020, typical anthracnose leaf spot symptoms with about 60% disease incidence were observed on FP cultivar WAAPP in a field at Manga (11°00′57.7″N, 0°15′54.2″W) in the Upper East region of Ghana. Early symptoms on leaves and stems consisted of tan or black, oval to irregular-shaped sunken spots (2 to 4 mm), which gradually extended and darkened with age. After 14 days, the infected leaves became chlorotic with “shot holes,” eventually reducing plant growth and tuber yield. Tissue segments from symptomatic leaves and stems (n = 20) were sterilized in 2% NaClO for 2 min, rinsed thrice with sterile distilled water, dried in a laminar flow hood, and placed on water agar. The cultures were incubated at 25°C in the dark for 3 days. Subsequently, 15 fungal isolates transferred to potato dextrose agar (PDA) by the single hyphal tip method displayed similar whitish-gray colonies with regular margins, reaching 62.12 to 68.98 mm in diameter after 7 days of incubation at 25°C. With aging, acervuli bearing abundant orange conidial masses formed, making the surface of the colony turn light salmon. Conidia were hyaline, aseptate, cylindrical with a smooth wall, rounded at both ends, and 14.65 ± 0.95 µm long and 5.4 ± 0.38 µm wide (n = 50). The appressoria were sparsely organized, dark brown, elliptical or irregularly shaped, and 10.05 ± 1.35 µm long and 5.81 ± 0.42 µm wide. The morphological traits of all the isolates were similar and matched those of Colletotrichum gloeosporioides (Cannon et al. 2008). For molecular identification, the internal transcribed spacer region (ITS), chitin synthase (CHS-1), β-tubulin (TUB2), and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) genes of two representative isolates, MB1 and MB2, were amplified using primers and PCR conditions outlined by Weir et al. (2012). BLASTn analyses using the isolates’ sequenced genes revealed ≥99% identity with the ITS (accession no. JX010152.1), CHS-1 (JX009818.1), TUB2 (GQ849434.1), and GAPDH (JX010056.1) sequences of the C. gloeosporioides type specimen in GenBank. Also, a maximum-likelihood phylogeny created in Mega IX with the sequences confirmed the identity of MB1 and MB2 as C. gloeosporioides. The accession numbers for MB1 and MB2 sequences deposited in GenBank are shown in the supplementary materials. The pathogenicity of isolates MB1 and MB2 was verified on 1-month-old FP plants raised in plastic pots. Ten healthy nonpigmented plants (WAAPP) were sprayed with an inoculum of each isolate (106 conidia/ml) and placed in a greenhouse at 27 ± 2°C and 80% relative humidity. The same test was repeated using pigmented FP plants (RT107). The controls involved five FP plants sprayed with sterile distilled water. Two weeks after inoculation, necrotic spots similar to those observed in the field developed on the FP plants. The control plants were symptomless. The same fungus inoculated was reisolated from diseased plants. While C. gloeosporioides is known to cause rot in stored FP tubers (Apuri et al. 2019), the incidence of a preharvest disease caused by the same pathogen has not been identified previously. To our knowledge, this is the first report of C. gloeosporioides causing anthracnose disease symptoms on FP in Ghana. An effective method to control this disease is needed to reduce FP damage and the spread of inoculum into storage facilities.The author(s) declare no conflict of interest.