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Characterization of a new subgroup of Rhizoctonia solani anastomosis group 1 (AG-1-ID), causal agent of a necrotic leaf spot on coffee

by Priyatmojo, A; Escopalao, V.E; Tangonan, N.G; Pascual, C.B; Suga, H; Kageyama, K; Hyakumachi, M.
Publisher: 2001ISSN: 0031-949X.Subject(s): COFFEA | COFFEA ARABICA | RHIZOCTONIA SOLANI | MORFOLOGIA FUNGICA | CAFE | ACIDOS GRASOS | ENFERMEDADES FUNGOSAS | ADN | SECUENCIA NUCLEOTIDICA | ENFERMEDADES DE LAS PLANTAS | ORGANISMOS PATOGENOS | RAPD | RFLP | FILIPINAS | COFFEA | COFFEA ARABICA | RHIZOCTONIA SOLANI | FUNGAL MORPHOLOGY | COFFEE | FATTY ACIDS | FUNGAL DISEASES | DNA | NUCLEOTIDE SEQUENCE | PLANT DISEASES | PATHOGENS | RAPD | RFLP | PHILIPPINES | COFFEA | COFFEA ARABICA | RHIZOCTONIA SOLANI | MORPHOLOGIE DE CHAMPIGNON | CAFE | ACIDE GRAS | MALADIE FONGIQUE | ADN | SEQUENCE NUCLEOTIDIQUE | MALADIE DES PLANTES | AGENT PATHOGENE | RAPD | RFLP | PHILIPPINES In: Phytopathology (EUA) v. 91(11) p. 1054-1061Summary: A new foliar disease on coffee (Coffea arabica) leaves was observed in Mindanao, Philippines, in 1996. The symptoms appeared as large circular or irregularly shaped necrotic areas with small circular necrotic spots (1 mm or less in diameter) usuallyfound around the periphery of the large necrotic areas. R. solani was consistently isolated from these diseased coffee leaves. Isolates obtained were multinucleate (3 to 12 nuclei per hyphal cell), had an optimum temperature for hyphal growth at 25°C, prototrophic for thiamine, and anastomosed with tester isolates belonging to R. solani anastomosis group 1 (AG-1). Mature cultures on potato dextrose agar (PDA) were light to dark brown. Sclerotia, light brown to brown, were formed on the surface of PDA andcovered the whole mature colony culture. Individual sclerotia often aggregated into large clumps (3 to 8 mm in diameter) and their colour was brown to dark brown. In pathogenicity tests, isolates from coffee caused necrotic symptoms on coffee leaves, whereas isolates of AG-1-IA (not isolated from coffee), 1-IB, and 1-IC did not. The results of analyses of restriction fragment length polymorphism of ribosomal DNA internal transcribed spacer, random amplified polymorphism DNA, and fatty acid profiles showed that R. solani isolates from coffee are a population of AG-1 different from AG-1-IA, 1-IB, and 1-IC. These results suggest that R. solani isolates from coffee represent a new subgroup distinct from AG-1-IA, 1-IB, and 1-IC. A new subgroup ID (AG-1-ID) isproposed.
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A new foliar disease on coffee (Coffea arabica) leaves was observed in Mindanao, Philippines, in 1996. The symptoms appeared as large circular or irregularly shaped necrotic areas with small circular necrotic spots (1 mm or less in diameter) usuallyfound around the periphery of the large necrotic areas. R. solani was consistently isolated from these diseased coffee leaves. Isolates obtained were multinucleate (3 to 12 nuclei per hyphal cell), had an optimum temperature for hyphal growth at 25°C, prototrophic for thiamine, and anastomosed with tester isolates belonging to R. solani anastomosis group 1 (AG-1). Mature cultures on potato dextrose agar (PDA) were light to dark brown. Sclerotia, light brown to brown, were formed on the surface of PDA andcovered the whole mature colony culture. Individual sclerotia often aggregated into large clumps (3 to 8 mm in diameter) and their colour was brown to dark brown. In pathogenicity tests, isolates from coffee caused necrotic symptoms on coffee leaves, whereas isolates of AG-1-IA (not isolated from coffee), 1-IB, and 1-IC did not. The results of analyses of restriction fragment length polymorphism of ribosomal DNA internal transcribed spacer, random amplified polymorphism DNA, and fatty acid profiles showed that R. solani isolates from coffee are a population of AG-1 different from AG-1-IA, 1-IB, and 1-IC. These results suggest that R. solani isolates from coffee represent a new subgroup distinct from AG-1-IA, 1-IB, and 1-IC. A new subgroup ID (AG-1-ID) isproposed.

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