Suppression of red rot caused by Colletotrichum falcatum on sugarcane plants using plant growth-promoting rhizobacteria

Abstract

Bacterial strains with ability to suppress Colletotrichum falcatum were isolated from the rhizosphere of sugarcane. Thirty nine candidates, chosen on the basis of in vitro antagonism, inhibited C. falcatum growth by 15-65% on test plates. Twenty two isolates causing 50% or more in vitro inhibition were screened for their root colonization ability and biocontrol activity on micropropagated sugarcane plants under greenhouse conditions. Twelve strains suppressed red rot infection in plantlets, but no significant correlation was observed between in vitro pathogen inhibition and in vivo disease suppression.However, isolates showing root colonization over 5.2 log 10 CFU g -1 of soil showed highest suppression of C. falcatum and reduction of red rot disease. Six strains with the capability to maintain a significant population in the sugarcane rhizosphere and with a high potential to control red rot were identified by 16S rDNA as Ochrobacterum intermedium NH-5, Pseudomonas putida NH-50, Bacillus subtilis NH-100, Bacillus subtilis NH-160, Bacillus sp NH-217 and Stenotrophomonas maltophilia NH-300.

Biological control of red rot in sugarcane by native pyoluteorin‐producing Pseudomonas putida strain NH‐50 under field conditions and its potential modes of action

“…The four native strains with proven efficacy to inhibit growth of G. tucumensis in vitro , to colonise sugarcane roots and to suppress red rot disease in glasshouse conditions17 produced different types of secondary metabolite and showed variable potential to control red rot disease under field conditions.…”

“…Red rot is the major constraint for sugarcane production, and developing a sustainable strategy to control this devastating disease is a current necessity. Previous experiments showed very rare prevalence (4%) of biocontrol agents in the rhizosphere of sugarcane 17. It has been extensively reported that biocontrol agents control plant diseases by producing a variety of secondary metabolites and exerting multiple modes of action.…”

“…The production of pyoluteorin by the P. putida strain NH‐50 might be responsible for its effective sugarcane root colonisation, in vitro antagonistic activity and in vivo disease control under glasshouse conditions17 and biocontrol activity under field conditions. Pyoluteorin, pyrrolnitrin, 2,4‐diacetylphloroglucinol and phenazine are the major determinants of the biocontrol activity of pseudomonads 8.…”

“…The test fungus Glomerella tucumensis and antagonistic bacteria Pseudomonas putida strain NH‐50, Pseudomonas sp. NH‐108 and unidentified strains NH‐150 and NH‐192 used in this study were previously isolated from infected sugarcane plants and the rhizosphere of healthy plants respectively 17 . Pseudomonas fluorescens strain CHA0, an effective and well‐characterised bioantagonist,18, 19 was used as positive control in this work.…”

“…Some strains isolated from the rhizosphere of sugarcane plants that had shown a wide range of in vitro antagonism against Glomerella tucumensis (Speg.) Arx & E Mull and had suppressed red rot infection on sugarcane plants under glasshouse conditions17 were selected. The aim of this study was to detect the production of secondary metabolites by these strains and evaluate their potential to control red rot disease on sugarcane plants under field conditions.…”