This work aims to isolate and screen the fungicidal endophytic bacterial strains for biocontrol efficacy against Phytophthora palmivora, a soil-borne pathogenic fungus that kills durian trees worldwide. Among more than 100 isolates, 6 strains were screened as potential fungicidal strains with inhibitory efficiency of 67.4-79.8%. Based on 16S rRNA gene sequencing and phylogenetic analysis, these strains were identified as Bacillus amyloliquefaciens EB.CK9, Bacillus methylotrophicus EB.EH34, Bacillus amyloliquefaciens EB.EH18, Bacillus siamensis EB.KN10, Bacillus velezensis EB.KN15 and Paenibacillus polymyxa EB.KN35. In greenhouse tests, the two strains P. polymyxa EB.KN35 and B. velezensis EB.KN15 significantly reduced the damage to diseased roots by P. palmivora (33.3 and 35.6%, respectively), increased the rate of survival of durian trees (only 20.8 and 22.9% plant death, respectively), and showed a positive effect on promoting durian plant growth. Notably, the potential fungicidal effect of last two strains against P. palmivora was recorded for the first time in this work. HPLC analysis showed that these strains can secret several plant growth-promoting compounds, including gibberellic acid (GA3), indole-3-acetic acid (IAA), kinetin, and zeatin. Of these, GA3 and zeatin were produced with a significant amount by both strains. The volatiles bio-synthesized by these isolates were also identified using GC-MS analysis, and some major volatiles were found as fungicidal agents. This study suggested that P. polymyxa EB.KN35 and B. velezensis EB.KN15 may be potential biocontrol candidates for durian P. palmivora and bio-fertilizers for the sustainable production of durian crops.

来源平台：APPLIED BIOCHEMISTRY AND MICROBIOLOGY