Induction of resistance against pine wilt disease caused by Bursaphelenchus xylophilus using selected pine endophytic bacteria

• Published in: Plant pathology Vol. 68; no. 3; pp. 434 - 444
• Main Authors: Kim, N., Jeon, H. W., Mannaa, M., Jeong, S.‐I., Kim, J., Lee, C., Park, A. R., Kim, J.‐C., Seo, Y.‐S.
• Format: Journal Article
• Language: English
• Published: Oxford Wiley Subscription Services, Inc 01-04-2019
• Subjects: Acids; Bacteria; Beetles; Bursaphelenchus xylophilus; Cell culture; chemical inducers; Disease resistance; Endophytes; Gene expression; Genes; induced resistance; Organic chemistry; Pine; Pine needles; pine wilt disease; pine wood nematode; Pseudomonas putida; Reduction; rRNA 16S; Salicylic acid; Seedlings; Strains (organisms); Wilt; Wood; γ-Aminobutyric acid
• ISSN: 0032-0862; 1365-3059
• DOI: 10.1111/ppa.12960

Pine wilt disease (PWD) is the most destructive disease threatening pine worldwide. The disease is mainly caused by the pine wood nematode, Bursaphelenchus xylophilus, which is vectored by pine sawyer longhorn‐beetles, Monochamus spp. This study aimed to select resistance‐inducing pine endophytic bacteria for management of PWD. To set up a defence‐related genes expression pattern for screening, four chemical inducers (salicylic acid, γ‐aminobutyric acid (GABA), β‐aminobutyric acid and α‐aminobutyric acid) were tested in vitro on pine calli and in vivo on pine seedlings. Treatment with GABA had the greatest reduction in PWD severity on pine seedlings. The pattern of defence‐related gene expression in calli treated with GABA was used to select potential resistance‐inducing bacterial strains. In addition, 92 bacterial strains were isolated from pine tree needles and stems and were tested for expression of defence‐related genes in pine calli in vitro. Among the tested strains, 13 showed a similar pattern to GABA treatment in at least four tested defence‐related genes and were selected for the seedling assay. From the seedling assay, three bacterial strains (16YSM‐E48, 16YSM‐P180 and 16YSM‐P39) showed significant reduction in PWD severity compared to the untreated control. Moreover, among the selected strains, cell‐free culture supernatant of strain 16YSM‐P180 significantly reduced PWD severity in inoculated pine seedlings. The selected strains were identified based on the 16S rRNA sequence as Pseudomonas putida 16YSM‐E48, Curtobacterium pusillum 16YSM‐P180 and Stenotrophomonas rhizophila 16YSM‐P39. These selected strains are suggested as potential alternatives for management of PWD by induction of systemic resistance.