Identification and biocontrol assay of Rossellomorea vietnamensis strain YJ21

Objective To screen bacteria from mangrove soil that can inhibit the growth and development of Sporisorium scitamineum, Magnaporthe oryzae, and Phytophthora capsici while promoting plant growth, thus providing biocontrol resources for managing crop diseases caused by these pathogens.

Method Bacteria were isolated from mangrove soil using the dilution spread plate method. The species of bacteria was identified through 16S rRNA sequencing and whole genome sequencing. The antagonistic effects of the bacteria against phytopathogens were evaluated via plate confrontation assay, spore germination test, in vitro leaf inoculation test, and pot inoculation experiment. Salkowski colorimetry was used to determine the indole-3-acetic acid (IAA) production capacity of the isolated bacterial strain, and the strain’s promotive effect on rice seed germination was evaluated via the seed soaking assay.

Result Strain YJ21 was isolated from the mangrove soil. It was identified as Rossellomorea vietnamensis through genomic evolutionary analysis. The inhibition rates of the YJ21 strain on the mycelial growth of M. oryzae and P. capsici were 34.62% and 39.87%, respectively. Its fermentation supernatant inhibited the teliospore germination in S. scitamineum teliospores, the inhibition rate of conidial germination in M. oryzae reached 90.48%, and the supernatant also reduced the pathogenicity of M. oryzae on rice. Furthermore, the YJ21 strain was capable of producing IAA and protease, and it significantly promoted the growth of root and shoot produced after rice seed germination.

Conclusion R. vietnamensis YJ21, isolated from mangrove soil, has a potential application for the biocontrol of rice blast.