Influência da temperatura na produção de antimicrobianos e no controle da antracnose e do crestamento bacteriano do feijão por bactérias biocontroladoras

Abstract

Biological control is a fundamental tool to minimize the damages caused by the excessive use of pesticides. However, to ensure consistent results it is necessary that the microorganisms used have the highest possible stability, even under adverse conditions. Knowing that temperature can influence the survival and the activities of microorganisms, the objective of this study was to evaluate in vitro the capacity of production of compounds related to the biocontrol, as well as to verify the biocontrol in vivo by bacteria preselected as biocontroller of common bean diseases, under different temperatures. For this, eight bacterial isolates DFs93-Bacillus cereus; DFs348-Bacillus sp.; DFs769-Bacillus cereus; DFs513-Pseudomonas veronii; DFs831-P. fluorescens; DFs842-P. fluorescens; DFs843- Rhodococcus sp.; DFs912- Rhodococcus sp., were studied in in vitro assays, evaluating growth, swarming motility, the capacity to produce hydrolytic enzymes (chitinase, caseinase and lecithinase), siderophores and ammonia, under five temperatures (17, 22, 27, 32 e 37ºC); as well as the antibiosis against Colletotrichum lindemuthianum by volatile or not compounds, under three temperature conditions (17, 22 e 27ºC); and in vivo, in common bean detached leaves, sprayed preventively with the biocontroller and incubated for 48h at different temperatures (17, 22, 27, 32 e 37ºC), for the biocontrol of anthracnose and bacterial common blight. It has been found that the capacity and speed of production of the compounds related to the biocontrol can be influenced by the incubation temperature. The bacteria studied have in vitro potential to control C. lindemuthianum through the production of antimicrobial compounds, volatile or not, at different temperatures. The spraying of bean leaves with the isolates DFs093, DFs348, DFs513, DFs769, DFs831 e DFs842 reduced the severity of anthracnose. The same isolates, and also DFs843 and DFs912, reduced the severity of bacterial common blight. Regardless of the treatments, the incubation of the bean leaves at different temperatures before the inoculation of the pathogen interferes in the incidence and severity levels of anthracnose and bacterial common blight, being the temperature of 37ºC which provided the highest averages of these variables for the two diseases studied, however, bacterial treatments maintained their biocontrol levels at all temperatures studied.