Ginger rhizome priming with lipopeptide-producing endophytic Bacillus species to control ginger soft-rot disease caused by Pythium myriotylum

Antagonistic endophytes previously isolated from the wild ginger congener, Zingiber zerumbet (L.) Smith were evaluated in the present study towards identifying candidate biocontrol agents (BCAs) for control of soft-rot disease caused by Pythium myriotylum. Bacillus isolates designated ZzER11 (B. amyloliquefaciens) and ZzER62 (B. subtilis), showing significant inhibition (> 80%) of P. myriotylum were characterized for production of lipopeptide (LP) biosurfactant. PCR screening for LP biosynthetic genes and MALDI-TOF-MS analyses revealed the production of surfactin, iturin and fengmycin (1010-1550 m/z range) classes of LPs by the selected Bacillus spp. Microscopic examination of P. myriotylum hyphae following confrontation experiments with ZzER11 and ZzER62 showed morphological distortions to mycelia including hyphal shrinkage and plasmolysis. Absolute inhibition of P. myriotylum hyphal growth was observed in presence of ZzER11 and ZzER62 LP extracts following disc diffusion assays. Biocontrol potential of ZzER11 and ZzER62 against the soft-rot disease was confirmed by priming ginger rhizomes with the endophytes. Results revealed effective control of soft-rot disease in endophyte-primed ginger rhizome even at high P. myriotylum zoospore concentration (10(4) zoospores/ g soil) with sprouts emerging after 30 days of infection (doi) and forming healthy plantlets. The selected antagonistic endophytic isolates from Z. zerumbet thus offer a solution for imparting resistance to ginger cultivars through microbiome manipulation.

Automated summary

Antagonistic endophytes isolated from wild ginger were evaluated as potential biocontrol agents for soft-rot disease caused by Pythium myriotylum. Bacillus isolates ZzER11 and ZzER62 showed significant inhibition of P. myriotylum and were characterized for the production of lipopeptide biosurfactants. These antagonistic endophytic isolates offer a promising solution for imparting resistance to ginger cultivars. Rating: 8 out of 10.