Biocontrol effects of the endophytic Bacillus halotolerans E16 against rice blast and genome analysis

Rice blast is a serious rice disease that leads to reduced yield and rice quality. Plant endophytes are beneficial to plants and help them antagonize pathogenic bacteria by synthesizing some active products. In this study, a strain of Bacillus halotolerans named E16, was detached from rice leaves. Confrontation results showed that E16 inhibited Magnaporthe oryzae by 90.66 ± 1.60 %. Further analysis demonstrated that E16 disrupted the integrity of the cell membranes of the mycelium, and E16 could grow at temperatures up to 50 °C and 150 mmol/L NaCl. Rice leaf blast inoculation test confirmed that E16 was effective in mitigating the attack of rice blast. Studies found E16 expression up-regulated the OsWRKY45, OsCEBiP and SA pathway OsPAD4 genes 10.42, 7.24 and 6.62-fold. The double-plate inversion assay showed VOCs produced by E16 significantly inhibited the growth of M. oryzae by 94.47 ± 0.4 %. Sixty-nine VOCs were identified in E16 using GC-MS, of 1-Dodecanol and 2-Pentadecanone were as dominant components. A total of 11 clusters of secondary metabolite synthesis genes were predicted in the whole-genome of E16, which lanthipeptide-class-iii, lanthipeptide-class-v and terpene were unknown gene clusters. In summary, E16 demonstrated excellent biocontrol potential as a rice blast antagonist strain, which provides an important reference for the green control of rice, especially saline rice diseases.