Bacillus-Mediated-Induced Systemic Resistance (ISR) Against Fusarium Corm Rot

Abstract

Fungi constitute the largest group of plant pathogens responsible for a range of serious plant diseases wherein fungal rot is a major disease associated with the pre- and post-harvest produce of plants. One of the most widely spread rot-causing fungi is Fusarium spp. that include F. oxysporum, F. graminearum, and F. solani that infect bulbs, tubers, rhizomes, and corms and lead to the decomposition of the tissue and finally death of the plant. Under low temperature, fungal infection usually remains dormant which under favorable climatic conditions converts in to disease. As there is a large decline in the annual yield of the crop plant due to Fusarium rots, so this has been an issue of concern since long. Earlier only chemical pesticides were used to control these infections but due to their ill effects on soil fertility, the focus has shifted to the use of biological control agents (BCA). Among BCA, a group comprised of bacilli, pseudomonads, and actinomycetes, together with nonpathogenic organisms Fusarium, Trichoderma, and Streptomyces, played an important role against phytopathogens. BCA helps in plant disease control and growth mainly by two methods: (i) secretion of antimicrobial compounds and (ii) induction of systemic resistance in plants. Bacillus species have been very effective BCA due to their ability to produce heat and desiccation-resistant spores and to withstand high temperature, unfavorable pH, lack of nutrients or water, and the ease of stable formulation preparation. This species can display almost all the mechanisms of a biocontrol and bio-stimulation/fertilization agent.