Paper presented at the 52nd CFCS Annual Meeting, Guadeloupe, July 10-16, 2016
CHARACTERIZATION OF COLLETOTRICHUM SPECIES AFFECTING YAM (DIOSCOREA SPP.) CROP IN PUERTO RICO Stephanie Fuentes, Merari Feliciano, Lydia I. Rivera and Agenol González. Department of Crops and Agro-Environmental Sciences, College of Agricultural Sciences, Mayagüez Campus. PO Box 9030, Mayagüez, PR 00681-9030. Keywords: Dioscorea spp. Colletotrichum, yam Abstract Yam anthracnose, caused by Colletotrichum gloeosporioides, is widely distributed in most yam-producing areas worldwide, causing losses of up to 90 % in the most palatable species Dioscorea alata and D. rotundata. The objective of this research was to characterize other species of this fungus affecting yam crop around the island. Twenty-two isolates of Colletotrichum spp. were obtained from the yam germplasm collection and private farms. Single-spore isolates were used for morphological and pathogenic characterization. DNA was extracted from isolates, and the genes ITS, GAPDH and TUB2 were amplified and sequenced. All isolates were pathogenic to yam on detached leave assay resembling anthracnose symptoms closely similar to those observed on naturally infected yam. Sequences obtained from these isolates had 97-100 % percentage of similarity with GenBank sequences. Based on morphological and molecular characterization nine species different of Colletotrichum gloesporioides were identified. These species were C. ignotum, C. tropicale, C. aoteora, C. truncatum, C. alatae, C. fructicola, C. theobromicola, C. siamense and C. cliviae. Also, one isolate of Colletotrichum gloesporioides was identified. Some of the identified species were pathogenic on D. rotundata previously reported as tolerant/resistant species of yam in Puerto Rico. ITS region was unable to separate some of these species in different clades, resulting β-tubulin and GAPDH the most discriminate genes to separate Colletotrichum species. These results are of significant importance to establish reliable control measures to increase yam production in the region. To our knowledge, this is the first report of these nine species causing anthracnose on the leaves of yam in Puerto Rico.
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