The ability of a new strain of Bacillus pseudomycoides to improve the germination of alfalfa seeds in the presence of fungal infection or chromium

Abstract

This study was conducted to improve alfalfa seed germination under stress conditions, elevated chromium concentrations or Fusarium infection by seed inoculation. The new Bacillus pseudomycoides strain BM1 was selected as the inoculant according to its ability to suppress plants pathogens and tolerate increased chromium concentrations. This rhizobacteria was isolated and identified based on 16S rDNA sequence from the soil of the rhizosphere of Medicago sativa. Additionally, in this study, the ability of strain BM1 to produce phytohormone Indole-3-Acetic Acid, siderophores, Hydrogen cyanide, extracellular lipase, cellulase, pectinase and to solubilize phosphate was examined. Strain BM1 showed in vitro strong inhibition rate of fungal growth of 59.68%, 48.72% and 43.59% for F. graminearum, F. proliferatum and F. oxysporum f. sp. medicaginis, respectively. To the best of our knowledge, this is the first time that Bacillus pseudomycoides has been reported to have antifungal potential and possess biosynthetic genes for fengycin and subtilin. This rhizobacteria can produce Indole-3-Acetic Acid, siderophores, extracellular lipase, cellulose and pectinase. Inhibition percentage of alfalfa seedling growth infected by F. oxysporum f. sp. medicaginis (in vitro) was reduced from 27.87% to 2.46%. The highest increase of root and shoot length of 12.36% and 21.43% was reached by applying BM1 culture inoculum. Seeds inoculated with BM1 showed no inhibition compared to the control in the presence of a chromium concentration of 0.11 mM L-1 and decreasing inhibition when chromium concentration increased in comparison to control samples (1.54-2.30 mM L-1). The new strain BM1 may be a good choice in phytoremediation of contaminated soil as well as a good active agent in biofertilizers or biofungicide.