Call Prefix : PR-T

Call Suffix : 1992

Call Cutter : D - PlPa 16

Location : SEARCA Library

Format : TD

Publisher : University of the Philippines Los Baños,

Publication Date : December 1992

Publication Place : Los Baños, Laguna, the Philippines :

Summary : One hundred bacterial isolates from soil samples collected from the rhizosphere of soybean seedlings grown in Chiang Mai, Thailand were tested for antagonism to seven root rot pathogens (Sclerotium rolfsii Sacc., Pythium aphanidermatum, (Edson) Fitzp., Phytophthora megasperma f. sp. glycinea Kuan and Erwin., Rhizoctonia solani Kuhn, Fusarium solani (App. & Wollenw.) Snyd. & Hans and F. oxysporum (Schlecnt.) Snyd. & Hans. Among the bacterial isolates, 48 proved antagonistic to one or more pathogens when grown on dual culture tests in the laboratory. This was based either on growth competition or antibiotic activity to the pathogen. Forty-two antagonistic isolates showed high potential as biological control agents against one or more pathogens in either blotter or tissue tests. These isolates were used further for controlling root rot disease of soybean in the greehouse. Soybean seeds (SJ.4) coated separately with cell suspension of different bacterial isolates and sown in sterilized soil amended separately with each of seven pathogens resulted in control of disease that causes rotting of seeds and roots. The bacterial antagonist coated-seeds also had improved stand, which resulted in greater fresh weight of plants and lower disease incidence. When the seeds were coated with the two most effective baterial isolates and sown in field plots amended separately with inoculum of each seven pathogens, the results were improved stand and greater seed weight and yield. Statistically significant yield increase up to 25 percent was noted in P. aphanidermatum-infested soil. The promising bacterial isolates were tentatively classified under genus PSEUDOMONAS, family PSEUDOMONADACEAE. The above prelimenary results suggest that once certain isolates of bacteria are established in the soil, soybean seedlings are partially protected from root rot pathogens in the field.