Biopesticides: Use of Rhizosphere Bacteria for Biological Control of Plant Pathogens

The pesticides used to control pests and diseases are also implicated in ecological, environmental and human health hazards. To reduce the deleterious effects of these agrochemicals, certain antagonistic microorganisms have been characterised from rhizosphere of different crop plants that suppress various plant diseases and thus, minimize the use of pesticides. The application of these specific antagonistic microorganisms in biological control of soilborne pathogens has been studied intensively in the last two decades. These beneficial rhizosphere microorganisms inhibit the pathogenic bacteria and fungi by producing antibiotics, bacteriocins, siderophores, hydrolytic enzymes and other secondary metabolites. The efficiency of these biocontrol products can be improved by manipulation of the environment, using mixtures of beneficial organisms, physiological and genetic enhancement of the biocontrol mechanisms, manipulation of formulations and integration of biocontrol with other alternative methods that provide additive effects. These biocontrol agents could be effectively utilised in sustainable agriculture for improving growth of crop plants

The rhizosphere microbiome and biological control of weeds: A review

The productivity of important grain crops wheat, rice and maize is adversely affected by various biotic and abiotic stresses. Weeds and phytopathogens are the major biotic stresses involved in biomass reduction and yield losses of these cereal crops. Various weeds compete with crop plants for natural resources viz. light, moisture, nutrients and space, and cause yield losses to agricultural produce. Weeds also increase harvesting costs and reduce quality of the farm produce. Weed management strategies include crop rotation, mechanical weeding or treatment with different herbicides. Although, sprays of different herbicides control various destructive weeds but their excessive use is environmentally unsafe and uneconomic. Indiscriminate use of these agrochemicals for weed control has resulted into considerable pollution of soil, groundwater and atmosphere. Therefore, effective biological weed management is an attractive approach for achieving the increased crop production to meet the food demands of the escalating global population. Many bacteria and fungi have been identified from the plant rhizospheres, which suppress the growth of weeds. The production of indole acetic acid, aminolevulinic acid, toxins and hydrogen cyanide has been correlated with the growth suppression of various weeds. Interestingly, inoculation with bioherbicides results in creation of biased rhizosphere leading to resource partitioning of nutrients towards growth stimulation of crop plants. Thus, inoculation of plants with bioherbicides has been found to increase germination percentage, seedling vigor, root and shoot growth, seed weight and increased grain, fodder and fruit yields. These environment-friendly biocontrol strategies for management of weeds are highly compatible with the sustainable agriculture