Biological control of necrotrophic plant pathogenic fungi: Tomato plants as a model
Biocontrol agent, Bacillus subtilis, was screened in a laboratory experiment against 6 necrotrophic fungi. These fungi were isolated from diseased plant materials. This biocontrol agent exhibited different potentials. It was highly effective against Fusarium oxysporum f. sp. lycopersici which causes tomato wilt and Fusarium oxysporum f. sp. fabae which causes broad bean wilt. It inhibited radial growth (RGI) by more than 75 %. However, it was less effective against Phytophthora infestans (64.7 % RGI), Botrytis cinerea (58.3 % RGI), Sclerotinia sclerotiorum (57.4 % RGI) Rhizoctonia solani (42.7 % RGI). When B. subtilis was applied to Tomato field, it exhibited different efficiency in suppressing Fusarium wilt. Time of implementation was critical for the efficacy of B. subtilis. It strongly suppressed wilt when applied 7 days before transplanting, by showing 72.7, healthy plant percentage (HP), followed by application at cotyledon stage (69.4 % HP). Salicylic acid was comparable to B. subtilis in protecting tomato against vascular wilt (68.3 % HP). Different mechanisms may be involved in the activity of B. subtilis in field. According to the laboratory test, diffusible suppressive substances as well as lytic enzymes may be produced by this biocontrol agent.
Egyptian Journal of Biotechnology Vol. 25 (1) 2007: pp. 1-12