Bacillus amyloliquefaciens strain enhances rhizospheric microbial growth and reduces root and stem rot in a degraded agricultural system

Abstract

The aim of this study was to evaluate the ability of Bacillus amyloliquefaciens B14 to improve the quality of a degraded soil in Lerma Valley, northwestern Argentina, as well as crop growth and yield, when inoculated on seeds of common bean (Phaseolus vulgaris L.) black cv. Nag 12. The effect on this soil infected with Macrophomina phaseolina (Tassi) Goidanich (Order: Botryosphaeriales) was also evaluated because in a previous work, B. amyloliquefaciens B14 was found to have an antagonistic effect against this pathogenic fungus. The strain effect was also compared with that of an agrochemical commonly used in the region (thiabendazole-fludioxonil-metalaxyl M). B. amyloliquefaciens B14 strain improved the nutrient availability, increasing soil organic carbon, total nitrogen and extractable P. In addition, B14 strain increased the activity of soil enzymes (AP, DHA and FDA), microbial respiration (MR) and microbial biomass carbon (MBC). This strain also significantly increased Trichoderma spp., Gliocladium spp., Pseudomonas spp. and actinomycete soil populations, and increased fungal and bacterial gene abundance. An increase in crop growth and yield was also determined. B. amyloliquefaciens B14 also reduced disease incidence caused by M. phaseolina, showing a greater effect than that of the agrochemical. Therefore, B. amyloliquefaciens B14 strain is a potential bioinoculant for bean in northwestern Argentina, where it may not only improve and protect common bean crop, but also enhance soil quality.