The antifungal activity and crop growth stimulation of growth-promoting rhizobacteria from banana rhizosphere soil

Objective To investigate the inhibitory effects of four banana growth-promoting rhizobacteria (PGPR) on Fusarium oxysporum f. sp. cubense race 4 and several other important crop pathogens.

Method The antifungal activity of PGPR was evaluated in petri dish. The promoting effect of PGPR fermented broth on plant growth was determined in a pot experiment.

Result and conclusion Four strains of PGPR including Bacillus subtilis, B. amyloliquefaciens, Pseudomonas otitidis and Ps. choloeaphtis isolated from rhizosphere soil of a healthy banana orchard showed a strong inhibitory effect on Fusarium oxysporum f. sp. cubense race 4, a causal agent of banana Fusarium wilt. The four bacteria also displayed antifungal activities against other tested crop pathogens including Alternaria solani, Rhizoctonia solani, Colletotrichum gloeosporioides Penz., C. musarum, F.oxysporum(Schl.) f.sp cucumerinum Owen, F. graminearum and Penorophythora litchi Chen. Ps. otitidis grew much faster than the other three bacteria, and the growth radius of Ps. otitidis was 2.75-, 2.61- and 2.70-fold relative to B. subtilis, B. amyloliquefaciens and Ps. choloeaphtis respectively. Ps. otitidis showed the best inhibitory effect on the tested crop pathogens, and the pathogen inhibition rate of Ps. otitidis to Fusarium oxysporum f. sp. cubense race 4, A. solani, R. solani, C. gloeosporioides Penz., C. musae, F.oxysporum (Schl.) f.sp cucumerinum Owen, F. graminearum and Pe. litchi was 50.70%, 62.95%, 70.85%, 68.10%, 58.58%, 59.30%, 51.34% and 63.08% respectively. The fermented broth of Ps. otitidis stimulated the seedling growth of tomatoes and corns, and it increased their shoot height by 16% and 33% respectively. It also increased the chlorophyll content of tomatoes by 40%. These results suggest that Ps. otitidis has strong antifungal activity against crop pathogens and also stimulate the growth of tomatoes and corns.