P33: Application of selected Streptomyces strains for the biological control of fungal root disease in tomato seedlings

The production of plum tomato seedlings has become in recent years, one of the main horticultural activities in central Mexico. Tomato root disease by fungal pathogens is a common cause of significant economic loss in commercial greenhouse operations. Three strains of the genus Streptomyces, have been used for biocontrol studies of root disease of tomato seedlings. In order to determine their relative activity against the main fungal pathogens of tomato, their antagonism and biocontrol potential were assesses both in vitro (in a plate assay), and in vivo, in a commercial scale germination unit for the production of greenhouse tomatoes.  Three selected, highly pathogenic strains of Fusarium sp, Pythium sp  and Rhizoctonia sp, were used throughout the experiments. In agar plate studies, Streptomyces sp 5a was the most active against Rhizoctonia; Streptomyces sp B4M6a proved to be the most important inhibitor of Fusarium sp; while Streptomyces sp C49D was the strongest antagonist of Pythium. For the greenhouse tests, a mixed formulation, M1, was tested. M1 contained equivalent concentrations of viable spores (5X105 UFC/g) for each one of the three Streptomyces strains.  Germination tests were performed with certified tomato seeds. A peat moss formulation was inoculated with either, the pathogen only, or the pathogen plus M1. The control with no pathogen or actinomycete inoculum had 94% germination; those inoculated with pathogen and no M1 showed less than 5% germination; whereas the experiments where both the fungal pathogen and M1 were inoculated showed germination from 45 to 51%.