Interaction between growth regulators-producing bacteria and root-rot fungi on tomato growth

ABSTRACT

The current study was carried out to study the interaction effect between plant growth promoting rhizobacteria [PGPR] and soil-borne pathogenic fungi on growth performance of tomato. PGPRs Azotobacter chroococcum [R19] and Bacillus megaterium var. phosphaticum [R44] strains used in the current study were isolated and identified in previous research by the same authors. Results obtained showed that A. chroococcum and B. megaterium var. phosphaticum gave high suppression against tomato root pathogenic fungi, i.e Fusarium oxysporum f.sp lycopersici and Fusarium solani. In vitro tests, clear zones around PGPR colonies can be attributed to the production of antibiotics-like substances, siderophores and cyanogens by suppressive PGPR strains. A lower percentage of tomato plants inoculated with a mixture of A. chroococcum and B. megaterium var. phosphaticum were infected than those inoculated with individual PGPRs . Growth characteristics, macro-nutrient content, endogenous phytohormones and photosynthetic pigments of tomato were significantly increased in the dual inoculated treatments compared to plants inoculated with either A. chroococcum or B. megaterium var. phosphaticum singly