Morpho-taxonomic and molecular identification of pathogen causing Anthracnose disease in field bean (Lablab purpureus L.) in Andhra Pradesh

Abstract

Field bean plants showing Anthracnose disease symptoms on leaves, stems and pods were collected from different Agro-climatic zones of Andhra Pradesh. The pathogen associated with Anthracnose disease was identified as Colletotrichum lindemuthianum (Sacc and Magn) based on symptoms, pathogenicity, morpho-taxonomic characters and molecular analysis . The Anthracnose disease symptoms on stem were observed as dark brown, slightly sunken cankerous elongated or spindle or diamond shaped necrotic lesions on different parts of field bean. Large numbers of acervuli were found scattered all over the necrotic area. . The pure culture of C. lindemuthianum was characterized by slow to medium growth, olive brown to pinkish red colonies. The aerial mycelium was soft, sticky and becoming flat on the upper surface and pinkish red with distinct zones on reverse side of PDA Petri plates. Conidiophores were formed as short single phiallides on hyphae, growing side by side and arising from stomatic mass of hypahe. The conidia were produced singly at the tip of the conidiophores. Conidia were hyaline, cylindrical, unicellular with obtuse ends, measured about 12.00 x 4.35μm. Orange colour acervuli, produced on 20 days old culture measured about 120-330μm. Setae were light brown to dark brown in colour measured about 74-118 x 2.3- 4.2 μm and conidia contained two oil globules. ITS region of rDNA from representative twenty isolates was amplified with ITS1 and ITS4 primers and amplicon size of 660 bp was obtained.