Characterization of Beauveria bassiana and its antagonism to Phomopsis vexans

Three isolates of Beauveria bassiana were characterized based on their morphological and cultural characteristics and their antagonistic properties were studied against Phomopsis vexans under in vitro and in vivo conditions. Mycelium of all the isolates of B.bassiana was hyaline, septate, branched with conidiophores arising from vegetative hyphae and bearing group of clustered flask shaped phialides. Conidia were borne on phialides and were single celled, globose to ellipsoidal and ranged between 4.9–5.7 x 3.8–3.9 µm. Sporulation was abundant in isolate Bb-III and moderate in Bb-I and Bb-V. The Texture of the colony was white smooth in Bb –I, white cottony in Bb –III and brownish white wrinkled in Bb –V. Culture filtrates of Beauveria isolates inhibited mycelial growth and sporulation of P.vexans.. Maximum reduction in mycelial weight and sporulation was obtained by 50% concentration of culture filtrates of isolate Bb- III. Aerial application of spore suspension and culture filtrates of Beauveria isolates reduced leaf blight incidence in field. However, spray of culture filtrates caused higher disease reduction as compared to spore suspension application. A strong antagonistic behaviour of culture filtrates of Beauveria isolates indicated extra cellular synthesis of inhibitory metabolites.