Abstract
Modern sustainable agricultural practices prefer to use biological agents for plant growth promotion, biocontrol and bioremediation as these are cost effective and eco-friendly. Our present study aims to investigate the effects of direct inoculation of selected consortia on plants to study its effects on supporting plant growth in the presence of root pathogen Sclerotium rolfsii and organophosphate pesticides Malathion (ML) and Methyl Parathion (MP). Candidate Plant Growth Promoting Microbial (PGPM) isolates chosen for the study are two bacterial isolates (PGPM2 a diazotrophic bacterium, PGPM9 a fluorescent Pseudomonad) and one fungal species (T103 a biocontrol fungus), originating from native agricultural fields of western U.P., India. Host plants inoculated with individual species showed a distributed growth enhancement pattern i.e., while isolate T103 improved root biomass, isolate PGPM9 enriched photosynthetic pigment content and isolate PGPM2 expanded root and shoot lengths. It appeared as though individual isolates showed a preference to enhance certain parameters over the other rather than exhibiting a uniform increment in all growth parameters. This preference to specific growth parameter over the other waned off in consortium studies where Sorghum bicolor inoculated with the consortium registered almost 2-fold increase in all parameters viz., root length, shoot length and overall biomass (root, shoot and total biomass) along with 23% rise in total chlorophyll content as compared to un-inoculated control. Selected consortia combination was able to provide better growth promotion in presence of pathogen Sclerotium rolfsii registering 58% increase in total biomass content while individual inoculation of biocontrol fungus T103 showed only 36% improvement. Selected consortia were also effective in plant growth promotion in presence of organophosphate pesticides ML and MP. More than two fold amplification was registered in all roots and shoot growth parameters studied when consortia was provided with ML and 28% increase was recorded when MP treatment was countered with consortia inoculation. All these results affirms our hypothesis that synergistic action of carefully selected PGPMs can escalate the benefits of plant growth promotion even in presence of pathogen and pesticide, hence this consortia may be a valuable option for sustained plant growth in modern agriculture systems.
Highlights
Present agricultural practices depend upon chemical fertilizers, pesticides and other chemicals for plant growth promotion and pathogen control with an intention to increase crop yield
Individual inoculation results by Plant Growth Promoting Microbial (PGPM) when compared with results from consortia inoculation experiments have proved that synergistic impact of consortia has better impact on plant growth promotion compared to distributed impact of individual inoculation
Studies related to plant growth supporting potential of PGP microbes were majorly confined to understand either biocontrol or plant growth benefits [46,50]. None of these studies explored building a consortium with an ability to provide growth promotion, disease resistance and mitigate negative impact of pesticide residues
Summary
Present agricultural practices depend upon chemical fertilizers, pesticides and other chemicals for plant growth promotion and pathogen control with an intention to increase crop yield. Chemical residues left in soil after cropping are accumulative, difficult to degrade and harmful to animals, plants and human health in general and to soil health in particular. They decrease soil fertility by gradually altering its chemical composition and rendering it non-fertile. Various microbes providing isolated benefits are well represented in literature as plant growth promoter or biocontrol agent [9,10,11,12,13] but still no chosen biofertilizer/biocontrol agent has been tested to provide protection against residual pesticide contamination which is common in agriculture soils. Commercial biofertilizers are mostly single species inoculants catering for isolated benefits such as providing either macronutrient (NPK) or biocontrol and acting with host specific bias which often results in non-consistent field performances
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