Screening, identification, and fermentation condition optimization of antagonistic endophytes from Oryza officinalis

Abstract:

[Background] Rice blast, one of three major diseases of rice, causes great losses to rice production every year. Biocontrol has become a key means for the prevention and control of this disease. However, there are few endophytes isolated from Oryza officinalis Wall. for the control of this disease at present. [Objective] To excavate the microbial resources against rice blast from the endophytes of O. officinalis. [Methods] The endophytes were isolated from O. officinalis, screened by the plate confrontation method, and identified based on morphological characteristics and 16S rRNA gene sequences. Furthermore, we optimized the medium, pH, temperature, and shaking speed for the fermentation of the strain screened out. [Results] The antagonistic strain Z5 was screened out and identified as Bacillus pumilus, with the inhibition rate of 96.43% on the mycelial growth of Magnaporthe grisea in the LB medium. Strain Z5 showed the best growth in the NYBD medium among the five medium tested (NYBD, CM, LB, NA, and YSP) and at pH 8.0–9.0, 35 ℃, and 250 r/min. [Conclusion] B. pumilus Z5 exerted a good inhibitory effect on the growth of M. grisea and can tolerate high temperature, acid, and alkali, demonstrating the potential of serving as a biocontrol agent for rice blast.