Long-term field application of a plant growth-promoting rhizobacterial consortium suppressed root-knot disease by shaping the rhizosphere microbiota

Abstract

Root-knot nematode (Meloidogyne spp.) is one of the most economically important plant parasitic nematodes, infecting almost all cultivated plants and resulting in severe yield losses every year. Plant growth-promoting rhizobacteria (PGPR) have been used extensively to prevent and control root-knot diseases and increase yield. In this study, the effect of a consortium of three PGPR strains (Bacillus cereus AR156, B. subtilis SM21, and Serratia sp. XY21; hereafter “BBS”) on a root-knot disease of cucumber was evaluated. The application of BBS significantly reduced the severity of root-knot disease by 56-72%, increased yield by 36-55%, and improved fruit quality by 14 -90% and soil properties by 1-90% relative to the control in the cucumber fields of the Nanjing suburb, Jiangsu Province, from 2015 to 2018. BBS altered the rhizosphere bacterial community. Compared with the control group, it significantly (FDR, p < 0.05) increased the abundance of 14 bacterial genera that were negatively correlated with the disease severity. Additionally, the redundancy analysis suggested that BBS-treated rhizosphere soil samples were dominated by disease-suppressive bacteria, including Iamia, Kutzneria, Salinibacterium, Mycobacterium, Kribbella, Pseudonocardia, Sporichthya, Sphaerisporangium, Actinomadura, Flavisolibacter, Phenylobacterium, Bosea, Hyphomicrobium, Agrobacterium, Sphingomonas, and Nannocystis, which were positively related to TOC, TN, TOM, DOC, NH4+-N and AP content. This suggests that BBS suppresses root-knot nematodes, and improves the soil chemical properties of cucumber by altering the rhizosphere microbial community.