Field suppression of fusarium wilt and microbial population shifts in tomato rhizosphere following soil treatment with two selected endophytic bacteria

Abstract

Two endophytic bacteria, Bacillus subtilis SV41 (KR818071) and B. amyloliquefaciens subsp. plantarum SV65 (KR818073), were assessed under field conditions for their capacity to control tomato Fusarium wilt in tomato and their effects on soil microbial activity. Six months after planting, Fusarium wilt severity, estimated through the vascular browning extent in tomato stems, was significantly reduced by 82.3 and 88.2% compared to control following bacterial treatments. The frequency of F.oxysporum re-isolation from roots, collars and stems was also significantly lowered in treated plants compared to controls. These effects were associated with a significant improvement, by 10.6 to 16.3%over control, in plant height and root fresh weight and an increase in fruit production by 8.4-12.5%. As for microbial activity, F. oxysporum population in the rhizosphere of tomato plants treated with B. subtilis SV41 and B. amyloliquefaciens subsp. plantarum SV65 was reduced by 87.5-91.7%compared to the initial soil (sampled before planting) and by 88.4-92.3% relative to the rhizospheric soil of untreated plants (control soil). A significant enhancement in the total culturable bacterial community was also noted in the rhizosphere of tomato plants treated with both strains compared to initial and control soils where a significant enrichment in Pseudomonas and actinobacteria community was recorded.