Bacterial Determinants and Plant Defense Induction: Their Role as Biocontrol Agents in Sustainable Agriculture

Abstract

In an environment consisting of harmful microorganisms, survival of plants mainly depends on effi cient microbial recognition and rapid defense mechanisms. After infection with a necrotizing pathogen, many plants develop resistance against attack by phytopathogens. This resistance is regarded as systemic acquired resistance, which is a key portion of plant defense against pathogen infection. Induction of acquired resistance in plants occurs mainly by enhancement of the levels of pathogenesis-related proteins and salicylic acid. Some groups of plantgrowth-promoting rhizobacteria are involved in an indirect mechanism, either by their antagonistic effect against phytopathogens or by induced systemic resistance (ISR) mechanisms in plants. ISR has been studied with respect to the underlying signaling pathways and to its application in crop protection. The signaling pathway regulating ISR functions independently of salicylic acid, and is mainly dependent on the plant hormones jasmonic acid and ethylene. Apart from these, NPR1, a defensive regulatory protein, is also involved in both systemic and acquired resistance in plants. In this chapter, the molecular and genetic relationship between basal resistance and induced resistance is highlighted.

Production, Purification, and Characterization of Bacillibactin Siderophore of Bacillus subtilis and Its Application for Improvement in Plant Growth and Oil Content in Sesame

“…Inoculation of siderophore producing B. subtilis LSBS2 significantly enhanced plant biomass, pigment content, iron, and oil content in the bioinoculant-treated sesamum plants as compared to the control (uninoculated) plants. Several investigations on the application of different species of Pseudomonas provided evidence of siderophores directly involved in the stimulation of plant growth and also protecting the plants against various biotic stresses [58,[70][71][72][73]. Likewise, an increased carotenoids level was observed in siderophores producing strain (Ros2) treated to wheat plants in the presence of pesticide stress [70].…”

“…Several investigations on the application of different species of Pseudomonas provided evidence of siderophores directly involved in the stimulation of plant growth and also protecting the plants against various biotic stresses [58,[70][71][72][73]. Likewise, an increased carotenoids level was observed in siderophores producing strain (Ros2) treated to wheat plants in the presence of pesticide stress [70]. Kusale and co-workers [74] isolated a potential siderophores-producing organism from the rhizosphere; this bacterium treated to sesame plants showed a drastic increase in the seed germination, shoot, root length and also recorded enhanced levels of chlorophyll.…”

Biological Control of Plant Pathogens: A Global Perspective

“…Based on the ability or behavior of the crops and biocontrol agents, PGPRs also act as biopesticides [ 33 ]. PGPRs are bacterial species including Alcaligenes , Azospirillum , Arthrobacter , Acinetobacter , Bradyrhizobium , Bacillus , Burkholderia , Enterobacter , Erwinia , Flavobacterium , Pseudomonas , Rhizobium , Azorhizobium , Bradyrhizobium , Allorhizobium , Sinorhizobium , Frankia , Mesorhizob , Azoarcus , Exiguobacterium , Methylobacterium , Paenibacillus , and Pantoea [ 29 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 ]. In reaction to diverse chemicals found in root exudates, beneficial bacterial communities in the soil are chemoattracted towards plant roots.…”

Plausible Role of Plant Growth-Promoting Rhizobacteria in Future Climatic Scenario

“…The gene and gene products involved in such type of biocontrol phenomenon have not been welldocumented. Systemic acquired resistance (SAR) is a defense mechanism activated in plant following the primary infection (Ryals et al 1996;Handelsman and Stabb 1996), while induced systemic resistance (ISR) utilizes organic acids and phytohormones to produce signals for stimulation of the host plant defense response against phytopathogens (Beneduzi et al 2012;Pieterse et al 2014;Patel et al 2016). ISR involves increase in physical and mechanical strength of the cell wall and modulation of physical and biochemical reactions of the cell to environmental stresses (Labuschagne et al 2010).…”