Ekta Khare

Effect of Indole-3-Acetic Acid (IAA) Produced by Pseudomonas aeruginosa in Suppression of Charcoal Rot Disease of Chickpea

The production of indole-3-acetic acid (IAA), by rhizobacteria, has been associated with plant growth promotion, especially root initiation and elongation. Isolate TO3 selected from 103 fluorescent pseudomonads, identified as Pseudomonas aeruginosa, showed maximum production of IAA. Isolate TO3 having biocontrol activity against Macrophomina phaseolina also showed production of siderophore and HCN was used to screen the role of bacterial IAA in reducing the level of charcoal rot disease occurrence in chickpea. Four IAA defective stable mutants of isolate TO3 having biocontrol activity against M. phaseolina were developed through 5-bromouracil mutagenesis. Mutant TO52 showed 76.47% reduction in production of IAA. Standard IAA was used in similar concentration as present in cell-free culture supernatant of wild isolate TO3 and its mutant TO52. The in vitro and in vivo study showed that IAA-defective mutant TO52 caused reduced biocontrol and plant growth promotory activity than wild isolate TO3. Standard IAA showed comparable biocontrol activity to the culture supernatant. To some extent better biocontrol and growth promotory activity in supernatant than standard IAA indicates the synergistic role of siderophore and HCN. The study clearly reports the role of bacterial IAA in suppression of charcoal rot disease of chickpea.

Plant Growth Promoting Rhizobacteria: Constraints in Bioformulation, Commercialization, and Future Strategies

Bioformulations for plant growth promotion continue to inspire research and development in many fields. Increase in soil fertility, plant growth promotion, and suppression of phytopathogens are the targets of the bioformulation industry that leads to the development of ecofriendly environment. The synthetic chemicals used in the agriculture to increase yields, kill pathogens, pests, and weeds, have a big harmful impact on the ecosystem. But still the chemicals rule the agroindustry. The aim of the review is to assess the constraints associated with the effective development of bioinoculant industry particularly in developing countries. Another objective of the review is to evaluate what should be explored in the future to uplift the stature of the bioinoculants. Bioformulations offer an environmentally sustainable approach to increase crop production and health, contributing substantially in making the twenty-first century the age of biotechnology.

Effects of Soil Environment on Field Efficacy of Microbial Inoculants

Although many microorganisms show good performance in specific trials, this is often not translated into consistent, effective plant growth promotion and biocontrol in diverse field situations. The key factors involved in the lack of success are rapid decline in the size of populations of active cells to levels ineffective to achieve the objective and variable production of required metabolites or poor colonization, following the introduction into soil. The physical, chemical, and physicochemical nature of soil and its indigenous microorganisms and predators influence the microbial population both quantitatively and qualitatively. Soil abiotic factors (e.g., texture, pH, temperature, and moisture) exert their (direct) effect on inoculant population dynamics by imposing stresses. On the other side, trophic competitions and antagonistic/synergic and predatory interactions with the resident microbial and fauna populations determine the field efficiency of inoculants. The aim of this review is to throw light on different soil environmental conditions that affect the survival of inoculated microbial strains in the field. A proper characterization of target soils and rhizospheres as habitats for introduced microbes is a key to the development of bioformulations that support beneficial microorganisms in the soil.

Phenetic, genetic diversity and symbiotic compatibility of rhizobial strains nodulating pigeon pea in Northern India

Pigeon pea (Cajanus cajan) is one of the most important legumes grown in the northern province of Uttar Pradesh, India. However, its productively in Uttar Pradesh is lower than the average yield of adjoining states. During the course of the present study, a survey of pigeon pea growing agricultural fields was carried out and it was found that 80% of plants were inadequately nodulated. The study was aimed to evaluate the pigeon pea symbiotic compatibility and nodulation efficiency of root nodulating bacteria isolated from various legumes, and to explore the phenetic and genetic diversity of rhizobial population nodulating pigeon pea growing in fields of Uttar Pradesh. Amongst all the 96 isolates, 40 isolates showed nodulation in pigeon pea. These 40 isolates were further characterized by phenotypic, biochemical and physiological tests. Intrinsic antibiotic resistance pattern was taken to generate similarity matrix revealing 10 phenons. The study shows that most of the isolates nodulating pigeon pea in this region were rapid growers. The dendrogram generated using the NTSYSpc software grouped RAPD patterns into 19 clusters. The high degree of phenetic and genetic diversity encountered is probably because of a history of mixed cropping of legumes. The assessment of diversity is a very important tool and can be used to improve the nodulation and quality of pigeon pea crop. It is also concluded that difference between phenetic and RAPD clustering pattern is an indication that rhizobial diversity of pigeon pea is not as yet completely understood and settled.

Rice OsPBL1 (ORYZA SATIVA ARABIDOPSIS PBS1-LIKE 1) enhanced defense of Arabidopsis against Pseudomonas syringae DC3000

The receptor-like cytoplasmic kinases (RLCK family VII) are required for plant defense against various pathogens. Previously, OsPBL1 (ORYZA SATIVA ARABIDOPSIS PBS1-LIKE 1) was isolated from rice as a potential RSV (rice stripe virus) resistant factor, but its physiological roles in plant defense are yet to be investigated. In this study, we demonstrated that OsPBL1increased defense against P. syringae in transgenic Arabidopsis. To ascertain the role of OsPBL1 gene in plant defense, OsPBL1 tagged with HA (i.e. Hemagglutinin) was overexpressed in Arabidopsis and examined for the resistance against Pseudomonas syringae pv. tomato DC3000 (i.e. Pst DC3000). At 3 dpi of Pst DC3000, transgenic Arabidopsis lines exhibited the reduced chlorotic lesion and propagation of P. syringae, compared to wild type. Elevated pathogen resistance of transgenic lines was correlated with increased H2O2 accumulation and callose deposition on the infected leaves. It was also revealed that expression levels of salicylic acid dependent genes such as PR1, PR2, and PR5, were induced higher in transgenic lines than wild type. Taken together, our data suggested that OsPBL1 exerted the role in defense against pathogen attacks in plant via mainly facilitating salicylic acid dependent pathway.

Correction to: Role of peptaibols and lytic enzymes of Trichoderma cerinum Gur1 in biocontrol of Fusarium oxysporum and chickpea wilt

The original article was published with the wrong title. The correct title is: Role of peptaibols and lytic enzymes of Trichoderma cerinum Gur1 in biocontrol of Fusarium oxysporum and chickpea wilt.