Diversidade genética de isolados de Phytophthora capsici de diferentes hospedeiros com base em marcadores RAPD, patogenicidade e morfologia

Genetic diversity of Phytophthora capsici isolates from different hosts based on RAPD markers, pathogenicity and morphology Phytophthora capsici is an omnivorous species and some of its hosts are cultivated in the state of Bahia. Morphological variations have been observed among isolates of P. capsici from rubber trees (Hevea brasiliensis), cacao (Theobromae cacao) and black pepper (Piper nigrum). RAPD markers and pathogenicity were used to study the genetic diversity within 22 isolates of the species. Eight isolates came from cacao, eight from rubber trees, three from green pepper (Capsicum annuum) (two collected earlier and one collected recently), and one each from black pepper, pumpkin (Cucurbita moschata) and tomato (Lycopersicon esculentum). Isolates from green pepper; pumpkin and tomato came from the State of Minas Gerais; the black pepper isolate was from the State of Pará; and the others from the States of Bahia and Espírito Santo. The genomic DNA of each isolate was extracted and amplified using eight decamer primers that generated 123 RAPD markers. Based on genetic distances and cluster analysis three groups were differentiated: one formed by cacao isolates, another by seven out of the eight rubber isolates and the third formed by the two earlier isolates of green pepper. Isolates of tomato, black pepper (recent), pumpkin, and one of rubber were genetically far from each other. Inoculations on fully developed but unripe fruits of cacao, rubber, tomato and green pepper, wounded or not, showed a rubber tree isolate that did not group with the others, infecting only wounded rubber pods. Only tomato and black pepper isolates infected green pepper fruits while all isolates tested infected cacao pods. The maintenance of all groups within P. capsici is discussed.