Taxonomic Studies on the Causal Fungus of Tomato Leaf Blight and Pathogenicity Test

Abstract

Stemphylium solani Weber is a causal of leaf blight disease of tomato in Thailand. The disease was noticed through gray spotted lesions appearing on the leaves which turned to larger necrotic reddish tissue. The conidia of this fungus are muriform, oblong or cylindrical with one contriction at the center . Some conidia are pointed at apical end and having smooth or somewhat rough outer wall. Their size is 33.7-52.5 x 15.0-22.5 microns. The conidia are formed singly at the swollen apex of a simple conidiophore, the length of which is 85.0-228.0 microns. The fungus sporulated sparsely on some culture media. However, profuse growth and conspicuous production of conidia were obtained at 25 C. under fluorescent light on V-8 juice agar medium (20-24 % V-8 juice), pH 6.0. Pathogenicity test on tomato leaves showed that conidial suspension at a concentration of 10 conidial per ml. produce symptoms on cv. Roma within 2 weeks. In cross inoculations onto 20 species of plants Solanum melongena Linn. (egg plant) and S.xanthocarpum Sch. & Wendl. Were infected.