Investigation on the biological control of Alternaria alternata

Alternaria alternata (Fr.) Keissl. which has a wide host range is an important fungal pathogen causing losses in yield in agricultural crops. The chemicals used for controlling this disease are directly toxic to beneficial microorganisms in soil. This study was carried out to determine the antifungal activities of a total 13 candidate bioagent bacterial isolates of Bacillus subtilis (TV-6F, TV-12H, TV-17C and TV 125 A), Bacillus megaterium (TV 87 A and TV 91 C), Bacillus pumilus (TV 67 C), Paenibacillus polyntyxa (TV 12E), Pantoea agglomerans (RK 92 and BRT-B), Pseudomonas flumrscens Biotip F (FDG 37), Bacillus thuringiensis subsp. kurstakii (BAB-410) and Bacillus sphaericus GC subgroup D (FD 49) and bioagent fungal isolates of Trichoderma harzianum (ET 4 and ET 14) against two isolates of A. alternata isolated from strawberry and cucumber on petri plate assays. B. pumilus TV 67C (87.63%-65.89%), B. subtilis TV 6F (77.61%-63.11%) and B. megaterium TV 87A (72.93%-68.87%) bacterial isolates were the most effective isolates against pathogenic fungi in in vitro and bioagent fungal isolates ET 4 and ET 14 inhibited pathogenic fungi grown in in vitro respectively 73.87% -83.33% and 55.85% -74.44%, too. Our results indicated that B. subtilis, B. pumilus, B. megaterium and T harzianum should be tested against A. alternata in field condition.