Serrano-Jiménez, Seylie M.

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    Diferenciación morfológica de cultivares de ñame (Dioscorea rotundata y Dioscorea alata) y especies de Colletotrichum spp. asociadas
    (2020-05-28) Serrano-Jiménez, Seylie M.; Feliciano-Rivera, Merari; College of Agricultural Sciences; Giraldo-Zapata, Martha C.; Rivera-Vargas, Lydia I.; Department of Crops and Agro-Environmental Sciences; Maldonado-Ramírez, Sandra L.
    In Puerto Rico, yam (Dioscorea spp.) is one of the most economically important tubers within the farinaceous screed. The most cultivated and consumed species are Dioscorea rotundata and Dioscorea alata. Imports of this crop on the island represent 80% of local demand. The lack of knowledge about yam species and its respective cultivars has been a problem that over the years has limited the production and adequate management of diseases in these crops. Colletotrichum spp. it is the most important genus of fungus in yams causing anthracnose, and the most destructive leaf disease. Correct management of these crops in terms of differentiation of cultivars and diseases requires tools that allow accurate identification of both plants and pathogens associated with them. The objectives of this research were to differentiate yam cultivars (Dioscorea alata and Dioscorea rotundata) through morphological descriptors and in silico analysis of RFLP, and in turn the identification of Colletotrichum species associated with the foliage anthracnose. Dioscorea spp morphological descriptors were evaluated in leaves, stems, roots, tubers and inflorescences, while the genetic analysis was performed evaluating RFLP of RbcL, MatK, and trnH-PsbA genetic regions. Colletotrichum spp. isolates identification was performed using morphological characteristics and for genetic identification ITS, TUB-2 and GAPDH genetic regions. With those isolates, growth curves and pathogenicity tests were performed following Koch's postulates. “Guinea Negro” (D. rotundata) cultivar turned out to be resistant to anthracnose and was differentiated from the D. alata species by the presence of spines on the stem, and tubers of cylindrical shape. While cultivars of D. rotundata differed from each other in the color of the stem, presence of spines in tuber roots, presence of aerial tubers, leaves color and dormancy of the tubers. The cultivar was differentiated from the rest of the D. rotundata cultivars by the presence of aerial tubers, and by having the shortest dormancy period. At the genetic level, the MatK gene proved to be a possible candidate for the study of species, while AluI and MseI enzymes can be considered as the most specific endonucleases for the separation of yam cultivars and species. Three Colletotrichum species were identified: C. karstii, C. siamense and C. tropicale. None of these identified species was pathogenic to “Guinea Negro” cultivar. Our research has shown that yam cultivars can be identified through morphological characters and RFLP analysis could be considered as an alternative to differentiate between cultivars of the same species.