Effect of certain fungal and bacterial phosphate solubilizing microorganisms on the fusarial wilt of tomato

M. R. Khan & S. M. Khan

Department of Plant Protection, Aligarh Muslim University, Aligarh 202 002, India

Abstract

A study was conducted under field condition in microplots to explore the feasibility of using certain fungal and bacterial phosphate solubilizing microoganisms (PSMs) through soil application and root-dip treatment to manage wilt of tomato caused by Fusarium oxysporum f. sp. lycopersici. Aspergillus awamori and A. nigerwere cultured on potato dextrose broth, whereas Pseudomona fluorescens and P. striata were incubated on nutrient broth. Inoculum of the wilt fungus was prepared on sorghum seeds and was added to soil at 1.5g/kg soil. For soil application pure culture on the broth was diluted in amplewater and added to soil at 2ml/kg soil. For root-dip treatment, roots tomato seedlings, Lycopersiconesculentum var. Pusa Ruby were dipped in the pure broth culture of the microorganisms for 30 minutes. The seedlings were planted in the microplots (3x2m) in the presence or absence of wilt fungus. The pathogenic fungus caused characteristic symptoms of wilt and significantly decreased the shoot dry weight and the yield by 36.6 and 34.7%, respectively. Soil application of A. awamori or P. fluorescens improved the yield of tomato (without wilt fungus) by 22 and 9%. Root-dip treatment with the former also improved the yield significantly. Application of PSMs, in general, suppressed the wilt fungus to a varied extent and decreased the wilt severitybeing greatest with A. awamori (29-37%). Fungicide treatment (carbendazim) decreased the severity of wilt by 8-19%. Greatest increase in the yield of infected plants was recorded due to soil or seed treatment with A. awamori (15-20%), followed by P. fluorescens (11-16%) and carbendazim (12-19%) compared to inoculated control.Soil population of wilt fungus (CFUs/g soil) in untreated plots was increased during first two months. Whereas in bioagent or fungicide treated plots, the population was gradually and significantly decreased during the four months of plant growth period. Greatest decrease in the population was recorded with A. awamori, followed by A. niger,P. fluorescens and carbendazim. On overall basis, soil application was found 5-10% more effective than root-dip treatment.