Bacillus subtilis rhizobacteria ameliorate heat stress in the common bean

Abstract

Bacillus subtilis can mitigate crop growth and yield under heat stress. We studied whether these benefits can be reproduced in the common bean (Phaseolus vulgaris L.). We hypothesized that B. subtilis strains AP-3 and AP-12 could improve bean crop performance under heat stress. Heat stress consisted of cultivation at 35 °C compared to pots at 25 °C in controlled environment chambers. Treatments were repeated on beans in vegetative and reproductive stages. Non-inoculated plants exhibited lower growth when exposed to heat stress as compared to inoculated plants. Particularly, the inoculation of B. subtilis increased shoot biomass (∼40%), shoot:root ratio (∼30%) and number of leaves (∼25%) in plants submitted to heat stress during their reproductive stage. The inoculation of B. subtilis increased the numbers of pods (∼45%) and flowers (∼70%), while decreased the abortion of flowers (∼15%) in plants submitted to heat stress. We conclude that inoculation of at least some Bacillus subtilis strains can ameliorate the negative effects of heat stress on the common bean. This is an important observation because heat stress has negative effects on both vegetative and reproductive development of plants, and with global warming crops are under increasing heat stress during the growing season.