Abstract
The present study evaluates the possible modes of action of antagonistic bacteria and their tolerance to UV radiation, temperature and osmotic stress. The partial 16S-23S rRNA gene sequencing of eight antagonistic bacteria had a high match with three bacterial genera: Curtobacterium, Pantoea and Bacillus. In this study, the three Bacillus isolates showed the most relevant production of enzymes, volatile organic compounds and antibiosis against Exserohilum turcicum. Respect to UV radiation and temperature Pantoea and Bacillus isolates were more tolerant; whereas the eight isolates were tolerant to osmotic stress in varying degree. The three Bacillus isolates have the greatest potential as biocontrol agents for foliar diseases in maize. The antagonistic action could be explained through different modes of action such as enzymes, volatile organic compounds and/or direct antibiosis by other secondary metabolites. Bacillus isolates tolerance to environmental stresses including UV radiation, temperature and osmotic stress is relevant for survival and persistence on the leaf surface. This work provides new information about the mode of action of antagonistic bacteria with proven efficacy against maize leaf pathogens. In addition, it provides information about the tolerance of antagonistic bacteria against different stress conditions. The data of the present study could contribute to the development of a successful foliar biofungicide.
Highlights
Maize (Zea mays L.) is one of the most important crops in Argentina
The present study evaluates the possible modes of action of antagonistic bacteria and their tolerance to UV radiation, temperature and osmotic stress
Analysis of 16S-23S rRNA sequences of antagonistic bacteria had a high match with three bacterial genera: Curtobacterium, Pantoea and Bacillus (Table 1)
Summary
Maize (Zea mays L.) is one of the most important crops in Argentina. During the 2017/2018 growing season the sowing area was increased by 35% reaching 5.4 million hectares [1]. Among the factors that limit yield, two foliar diseases have become important in recent years. Common rust is an endemic disease in maize growing area caused by Puccinia sorghi, occurring all seasons with varying degrees of intensity according to hybrid susceptibility, pathogen biotypes and environmental conditions during the crop cycle [2]. Fungicides based on strobilurin + triazoles are the most effective method to control foliar diseases [4]. Biological control is defined as an “environmentally-friendly” strategy using microorganisms or their derivatives to reduce a targeted pathogen. The narrow spectrum of biological control agents (BCAs) should provide an optimum efficacy without affecting non-targeted organisms [6]. It is known that a successful BCA has several mechanisms of action capable of working synergistically [7]
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