Abstract

SOLANO-BAEZ, Alma Rosa et al. Biocontrol of damping-off of zucchini squash seedlings with Bacillus subtilis QST 713. Rev. mex. fitopatol [online]. 2021, vol.39, n.2, pp.302-313.  Epub Nov 03, 2021. ISSN 2007-8080.  https://doi.org/10.18781/r.mex.fit.2101-2.

Bacillus subtilis exhibits antagonistic activity against plant pathogens. In the present study, the fungi associated with damping off in zucchini squash seedlings were identified and the efficacy of B. subtilis strain QST 713 was evaluated against the combined infection of the isolated fungi. The pathogens were isolated from zucchini squash seedlings with symptoms of damping off. Seedlings of zucchini squash var. Gray zucchini were inoculated with propagules of three pathogens at a concentration of 4×105 CFU of each pathogen. The effectiveness of B. subtilis (2, 4 y 6×107 UFC mL-1) was evaluated and compared with methyl thiophanate + propamocarb hydrochloride (preventive and curative). The incidence was assessed at three, six, nine and 12 days (dai). Three fungi out of 100 isolates were isolated and identified: Phytophthora capsici (62%), Rhizoctonia solani (26%) and Fusarium oxysporum (12%). The efficiency of B. subtilis was observed, with a reduction in the incidence of the disease as the concentration was increased. Twelve days after inoculation, the incidence of damping off in B. subtilis treatments ranged from 18.3 to 41%. The B. subtilis treatment (6×107 CFU mL-1) was statistically equal to methyl thiophanate + propamocarb hydrochloride (curative). The strain QST 713 of B. subtilis controlled 81.7% the damping off of zucchini squash seedlings, applied preventively at a concentration of 6×107 CFU mL-1.

Keywords : Cucurbita pepo; seedlings; thiophanate-methyl; propamocarb hydrochloride.