Development of formulations of biological agents for management of root rot of lettuce and cucumber

The effect of various carrier formulations of Bacillus subtilis and Pseudom onas putida were tested on germination, growth, and yield of lettuce and cu cumber crops in the presence of Pythium aphanidermatum and Fusarium oxyspor um f.sp. cucurbitacearum, respectively. Survival of B. subtilis and P. puti da in various carriers under refrigeration (about 0%C) and at room temperat ure (about 22%C) was also studied. In all carrier formulations, B. subtilis strain BACT-0 survived up to 45 days. After 45 days of storage at room tem perature (about 22%C), populations B. subtilis strain BACT-0 were significa ntly higher in vermiculite, kaolin, and bacterial broth carriers compared w ith other carriers. Populations of P. putida were significantly higher in v ermiculite, peat moss, wheat bran, and bacterial broth than in other carrie rs when stored either under refrigeration (about 0%C) or at room temperatur e (about 22%C) for 15 or 45 days. Germination of lettuce seed was not affec ted in vermiculite, talc, kaolin, and peat moss carriers, but germination w as significantly reduced in alginate and bacterial broth carriers of B. sub tilis compared to the non-treated control. Germination of cucumber seed was not affected by any of the carriers. Significantly higher fresh lettuce an d root weights were observed in vermiculite and kaolin carriers of B. subti lis compared with P. aphanidermatum-inoculated control plants. Lettuce trea ted with vermiculite, and kaolin carriers of B. subtilis, or non-inoculated control lettuce plants had significantly lower root rot ratings than talc, peat moss, bacterial broth, and P. aphanidermatum-inoculated control plant s. Growth and yield of cucumber plants were significantly higher in vermicu lite-based carrier of P. putida than the other carriers and Fusarium oxyspo rum f.sp. cucurbitacearum-inoculated plants.