Combination of biocontrol bacteria for rice seeds microbiolization: incidence and transmission of Bipolaris oryzae, and plant growth

Combinação de bactérias biocontroladoras para microbiolização de sementes de arroz: efeito na incidência, transmissão de Bipolaris oryzae e crescimento vegetal

Abstract:

Several fungi species are associated with rice seeds, mainly Bipolaris oryzae, since it can kill seedlings and reduce production. Thus, the objective of this research was to study the potential of pre-selected combinations of rhizobacteria [DFs-C4 (DFs185/DFs416/DFs418) and DFs-C5 (DFs306/DFs416/DFs418)], when compared to their use individually (DFs185, DFs306, DFs416, DFs418), besides DFs223, evaluating the effect on the incidence and transmission of B. oryzae, incidence of phytopathogenic fungi and in the initial growth after rice seeds microbiolization. Seeds of cultivars BRS Pelota and BRS Querência (four lots each) were immersed in suspension of these bacteria or in saline solution (control) under agitation (for 30 minutes at 10 ºC). The fungi incidence was evaluated on blotter test. The pathogen transmission was assayed in sterilized vermiculite and humid chamber at 25 ± 2 ºC. After 15 days, the severity of the symptoms and the plant growth were evaluated. For both cultivars, the best treatments were DFs185 and DFs306, reducing the fungi incidence, including B. oryzae, as well as its transmission to seedlings, resulting in seedling length increase. The combination of biocontrol bacteria, individually efficient, did not result in a lower fungi incidence, or a reduction in the transmission of B. oryzae to the seedlings or an initial increase in seedling growth. Therefore, these rhizobacteria are more efficient when used individually.

Index terms: biological control; brown spot of rice; PGPR