Biological potential of Pseudomonas sp. BS1 in the control of Phytophthora root rot of soybean

In this study, the biological potential of Pseudomonas sp. BS1 in the control ofPhytophthora root rot of soybean was investigated. Fermentation filtrates ofPseudomonas sp. BS1 inhibited zoosporangium formation and zoospore germination ofPhytophthora sojae (P. sojae), and the inhibitory effect gradually weakened with the increasing filtrate dilution. It had a relatively strong inhibition on hyphal growth of P. sojae, and the inhibition rate of stock solutions reach 95.9%; as dilution increased, the inhibition gradually weakened. The results indicated that Pseudomonas sp. BS1 can inhibit normal growth and development of P. sojae, and pathogen reproduction. Through investigating the controlling effect of Pseudomonas sp. BS1 fermentation filtrates on Phytophthora root rot of soybean under greenhouse conditions, we found that pre-treatment with fermentation filtrates had a preventive effect on disease caused by P. sojae, and post-inoculation treatment with fermentation filtrates had a therapeutic effect. Simultaneous treatment with fermentation filtrates and zoospore suspension had best controlling effects. These results will provide a theoretical basis for the biological control of Phytophthora root rot of soybean using Pseudomonas sp. BS1.   Key words: Pseudomonas, Phytophthora, zoosporangium, zoospore, biological control.