Glucanolytic rhizobacteria associated with wheat- maize cropping system suppress the Fusarium wilt of tomato (Lycopersicum esculentum L)

Abstract Tomato wilt caused by F. oxysporum (Fox) is one of the most destructive diseases, which causes qualitative and quantitative losses. In the present study, the bio-efficacy of glucanolytic bacteria was assessed on tomato against Fusarium wilt under net house conditions. A 178 rhizobacteria were isolated from the wheat-maize cropping system of arid and semi-arid regions. Only ten out of 178 rhizobacteria produced glucanases. The glucanolytic bacteria exhibited variable ability to produce β-1, 3/4-glucanases (0.11 – 0.30 U/mL). The glucanase production was higher at pH 7 (SZ =7.89 mm - 14.11 mm) followed by pH 9 (SZ=5.78 mm - 10.56 mm) and pH 5 (SZ=5.55 mm - 10.00 mm). The glucanolytic bacteria MAZ 10SR, 13, 18, 32, 48, 51, 73, 86, 117, 151 & 165 suppressed F. oxysporum (43–68%) causing tomato wilt and other phytopathogens viz F. moniliforme (44–63%), M. phaseolina (42–65%) and P. oryzae (42–67%). The glucanolytic bacteria also produced different antifungal metabolites/compounds viz siderophores, protease, and lipopeptide antibiotic surfactin. In planta assays indicated the ability of glucanolytic bacteria Bacillus subtilis MAZ 10SR, 51, 117 & 165 to colonize the tomato rhizosphere by 7.4 – 8.9 log CFU/g of soil. They decreased the Fusarium wilt incidence with disease severity of 22–31% as compared to that of control (disease severity = 56%). A significant quantity of glucanases (0.33–0.70 U/mg of soil) was recovered from the tomato rhizosphere inoculated with the effective glucanolytic bacteria. The glucanolytic rhizobacteria were identified as Achromobacter mucicolens, Enterobacter cloacae, Serratia marcescens, and Bacillus spp. by 16S rRNA gene analysis. The utilization of glucanolytic bacteria could be a worthy strategy in the biological control of soil-borne pathogens.