Antagonism of black rot in cabbage by mixtures of plant growth-promoting rhizobacteria (PGPR)

Abstract

Black rot, caused by Xanthomonas campestris pv. campestris (Xcc) (Xanthomonadales: Xanthomonadaceae), is the most important and potentially destructive disease of cabbage. Twenty-three plant growth-promoting rhizobacteria (PGPR) strains were tested for antibiosis against Xcc in vitro. Seven strains with antibiosis activity significantly reduced disease in the greenhouse. Two mixtures of PGPR strains and four individual strains were then tested three times in the greenhouse and one time in the field. In the greenhouse test, all treatments resulted in significant disease suppression. Mixture-2 and strain AP218 caused the highest and most consistent disease reduction in two of the three trials. In the field test, both mixtures and two individual strains significantly reduced disease incidence and disease severity. In conclusion, mixture-2 exhibited consistent biocontrol of black rot of cabbage.