Promotion of growth and biocontrol of brown patch disease by inoculation of Paenibacillus ehimensis KWN38 in bentgrass

Abstract

Brown patch disease, caused by Rhizoctonia solani, is one of the most serious diseases of turf grasses including bentgrass (Agrostis palustris). This disease is usually controlled by different formulations of synthetic fungicides. In this study, two pot trials were carried out to investigate the biocontrol potential of the antagonistic strain Paenibacillus ehimensis KWN38 against R. solani, and to examine the growth response of bentgrass to the inoculated strain. Bentgrass mats with root system in plastic boxes were treated with winter grass medium (W), W plus P. ehimensis KWN38 inoculation (WP), summer grass medium (S), S plus P. ehimensis KWN38 inoculation (SP), fertilizer (F), and F plus fungicide (FF) once every 10 days for three months. After the first month, all pots were infected with R. solani. Sixty days after infection, the leaves of bentgrass in all control treatments (W, S, and F) showed high levels of infection, with significantly higher values than those of WP, SP and FF. The leaf fresh and dry weights of bentgrass innoculated with P. ehimensis KWN38 were all greater than the control treatments W, S and F. Similarly, both fresh and dry weights of the roots and the chlorophyll contents of bentgrass in WP and SP were significantly higher than those of W, S, F and FF. Moreover, bentgrass innoculated with P. ehimensis KWN38 grew faster and showed greater growth performance as compared to the other treatments in the second pot trial with infected bentgrass. A butanol extract of the P. ehinmensis KWN38 culture supernatant significantly reduced the number of fungal colonies initiating from sclerotial fragments on potato dextrose agar. The growth of monilioid cells of R. solani was delayed by treatment with P. ehimensis KWN38 culture broth, while they elongated earlier into thinner structures in the control treatment. In conclusion, the antagonist P. ehimensis KWN38 can be considered as an effective biocontrol agent against brown patch disease, as well as a promising plant growth promoting bacteria of bentgrass.