Isolation, identification and in vitro evaluation of Bacillus spp. in control of Magnaporthe oryzae comparing evaluation methods

Abstract

Environmentally friendly technologies, such as the use of bacteria (e.g. Bacillus spp.) to control fungal diseases of rice (Oryza sativa L.), represent a promising alternative for the sustainability of agricultural ecosystems. The present work aimed to isolate, identify, and evaluate (in vitro) various Bacillus spp. from the rice phylloplane for their potential to control the rice fungus Magnaporthe oryzae. Samples were taken from the phylloplane of healthy young rice plants growing in commercial fields in ten municipalities of Maranhão (Brazil), and Bacillus spp. were subsequently isolated and molecularly identified. Both experiments utilized a randomized design, and data were submitted to analysis of variance as well as means comparison by the Tukey test. Twelve bacterial isolates were obtained and identified. Using a control isolate (B25), four in vitro M. oryzae-inhibition methods were compared, with the ‘circle’ method ultimately providing the highest mycelium growth inhibition. The most promising experimental isolates for biological control were then identified as B. methylotrophicus isolates B41, B31, and B22, which achieved 90.41, 69.47, and 67.55% inhibition, respectively. This study demonstrates the potential of Maranhão Bacillus spp. isolates for use as biological fungal-control agents.