Bio control of <i>Rhizoctonia solani </i>Root-Rot by AM fungi and <i>Pseudomonas fluorescens</i>

Abstract

Experiments were carried out under field conditions to study the effect of two arbuscular mycorrhizal fungal (AMF) bio control agents against root-rot pathogen <i>Rhizoctonia solani </i>infecting <i>Phaseolus vulgaris </i>(Rabi Rajma). Bio control agents <i>viz</i>, AMF and <i>Pseudomonas fluorescens </i>(Pf) alone or in combination promoted plant-growth and reduced the root-rot disease severity. Both the AM fungi induced better plant growth and decreased disease incidence as compared to control i.e. <i>R. solani </i>(Rs) alone treatment. Besides combined AMF, <i>P. fluorescens </i>also proved beneficial for disease control. AMF+Pf combinations gave better results against root-rot disease. Bacterial suspension of <i>P. fluorescens </i>inhibited the mycelial growth of <i>R. solani </i>and also facilitated the AMF colonization in plant roots resulting in the increased plant growth and biomass. A comparative study of cellular total soluble sugars, ortho-dihydric phenol, flavonols and epicuticular wax was also done. Sugar content was at minimum 75 days after sowing (DAS) in untreated control plants as compared to plants inoculated with either AMF or Pf or either of the two combined with <i>R. solani</i>. Epicuticular wax content of rajma leaves forms physical barrier against various pathogens protecting the plants. It was also significantly increased when the plants were treated with different AMF as compared to diseased control. However, wax content decreased in <i>R. solani </i>alone treated plants 75 DAS as compared to that 45 DAS.