Pseudocercospora griseola causing Angular Leaf Spot on Phaseolus vulgaris produces1,8-Dihydroxynaphthalene-Melanin

SAPARRAT MCN, · FERMOSELLE GE, · STENGLEIN SA, · AULICINO MB, · BALATTI PA

MYCOPATHOLOGIA

SPRINGER

Año: 2009 vol. 168 p. 41 - 47

0301-486X

Pseudocercospora griseola is the causative agent of angular leaf spot, a disease of common bean (Phaseolus vulgaris). It has undergone parallel micro-evolution with its host and two major groups have been defined, “Middle American” (P. griseola f. griseola) and “Andean” (P. griseola f. mesoamericana). The objective of this study was to analyze the nature and the level of the dark pigment synthesized by representatives of each group. After 21 days of incubation on potato-dextrose-agar medium P. griseola f. griseola isolate S3b developed colonies with diameters of 17.5 ±1.3 mm and concentric rings of pigmentation. Isolate T4 of P. griseola f. mesoamericana presented smaller colonies (9.9±0.3 mm) with a uniform dark-gray colour. Both isolates Sb3 and T4 produced the same pigment a 1,8-dihydroxynaphthalene-melanin, although different in quantity and structural features as suggested by the IR-spectrum. The P. griseola f. griseola isolate S3b had a higher growth rate and melanin content as well as sensitivity to melanin synthesis inhibitors compared to the isolate T4 of P. griseola f. mesoamericana. These results suggest a possible link between melanin and growth in P. griseola. is the causative agent of angular leaf spot, a disease of common bean (Phaseolus vulgaris). It has undergone parallel micro-evolution with its host and two major groups have been defined, “Middle American” (P. griseola f. griseola) and “Andean” (P. griseola f. mesoamericana). The objective of this study was to analyze the nature and the level of the dark pigment synthesized by representatives of each group. After 21 days of incubation on potato-dextrose-agar medium P. griseola f. griseola isolate S3b developed colonies with diameters of 17.5 ±1.3 mm and concentric rings of pigmentation. Isolate T4 of P. griseola f. mesoamericana presented smaller colonies (9.9±0.3 mm) with a uniform dark-gray colour. Both isolates Sb3 and T4 produced the same pigment a 1,8-dihydroxynaphthalene-melanin, although different in quantity and structural features as suggested by the IR-spectrum. The P. griseola f. griseola isolate S3b had a higher growth rate and melanin content as well as sensitivity to melanin synthesis inhibitors compared to the isolate T4 of P. griseola f. mesoamericana. These results suggest a possible link between melanin and growth in P. griseola.