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Microbial interactions occurring in rhizosphere may play important roles in providing protection against phytopathogens. Induction of phenolic compounds and their modulation in leaf and collar region was investigated upon challenge inoculation with Sclerotinia sclerotiorum in pea plants untreated and treated with beneficial microbes viz. Bacillus subtilis BHHU100, Trichoderma harzianum TNHU27 and Pseudomonas aeruginosa PJHU15 either singly or in the form of consortium. Changes in phenolic compounds in both leaves and collar region indicated that the induced response was systemic in nature altering the physiological status of the host plant. The phenylpropanoid metabolism was strongly involved in providing resistance against S . sclerotiorum challenge; especially in the plants treated with microbes in consortium, where the response was exaggerated in order to cope up with the biotic stress induced by the pathogen. Enhanced accumulation of phenolics viz., shikimic acid, gallic acid, chlorogenic acid, syringic acid, p-coumaric acid, cinnamic acid, salicylic acid, myricitin, quercetin and kaempferol occurred both in leaf and collar tissue. [ABSTRACT FROM AUTHOR]

The beneficial plant-microbe interactions play crucial roles in protection against large number of plant pathogens causing disease. The present study aims to investigate the growth promoting traits induced by beneficial microbes namely Pseudomonas aeruginosa PJHU15, Trichoderma harzianum TNHU27, and Bacillus subtilis BHHU100 treated singly and in combinations under greenhouse and field conditions to control Sclerotinia sclerotiorum. Plants treated with three microbe consortium enhanced plant growth maximally both in the presence and absence of the pathogen. Increase in plant length, total biomass, number of leaves, nodules and secondary roots, total chlorophyll and carotenoid content, and yield were recorded in plants treated with microbial consortia. Also, a decrease in plant mortality was observed in plants treated with microbial consortia in comparison to untreated control plants challenged with S. sclerotiorum. Furthermore, the decrease in disease of all the treatments can be associated with differential improvement of growth induced in pea. [ABSTRACT FROM AUTHOR]

Microbial consortia may provide protection against pathogenic ingress via enhancing plant defense responses. Pseudomonas aeruginosa PJHU15, Trichoderma harzianum TNHU27 and Bacillus subtilis BHHU100 were used either singly or in consortia in the pea rhizosphere to observe proteome level changes upon Sclerotinia sclerotiorum challenge. Thirty proteins were found to increase or decrease differentially in 2-DE gels of pea leaves, out of which 25 were identified by MALDI-TOF MS or MS/MS. These proteins were classified into several functional categories including photosynthesis, respiration, phenylpropanoid metabolism, protein synthesis, stress regulation, carbohydrate and nitrogen metabolism and disease/defense-related processes. The respective homologue of each protein identified was trapped in Pisum sativum and a phylogenetic tree was constructed to check the ancestry. The proteomic view of the defense response to S. sclerotiorum in pea, in the presence of beneficial microbes, highlights the enhanced protection that can be provided by these microbes in challenged plants. [ABSTRACT FROM AUTHOR]

Oxalic acid (OA) is an important pathogenic factor during early Sclerotinia sclerotiorum-host interaction and might work by reducing hydrogen peroxide production (H2O2). In the present investigation, oxalic acid-induced cell death in pea was studied. Pea plants treated with biocontrol agents (BCAs) viz., Pseudomonas aeruginosa PJHU15, Bacillus subtilis BHHU100, and Trichoderma harzianum TNHU27 either singly and/or in consortium acted on S. sclerotiorum indirectly by enabling plants to inhibit the OA-mediated suppression of oxidative burst via induction of H2O2. Our results showed that BCA treated plants upon treatment with culture filtrate of the pathogen, conferred the resistance via. significantly decreasing relative cell death of pea against S. sclerotiorum compared to control plants without BCA treatment but treated with the culture filtrate of the pathogen. The results obtained from the present study indicate that the microbes especially in consortia play significant role in protection against S. sclerotiorum by modulating oxidative burst and partially enhancing tolerance by increasing the H2O2 generation, which is otherwise suppressed by OA produced by the pathogen. [ABSTRACT FROM AUTHOR]

Microbial populations have diverse roles within rhizosphere where interactions among distinct microorganisms along with the host may lead to mutualistic associations. The present study aimed to investigate the nutritional and antioxidant qualities of seeds and pericarp of pea raised from seeds treated with beneficial microbes namely Bacillus subtilis BHHU100, Trichoderma harzianum TNHU27 and Pseudomonas aeruginosa PJHU15 either singly and/or in consortia. A significant increase in total phenolic, flavonoid, ascorbic acid and protein contents, free radical scavenging activity, hydroxyl radical scavenging activity, iron chelation and reducing power were observed in the seeds and pericarp of pods treated with a consortium of microbes in comparison to control pods. Also, the differential accumulation of phenolic compounds, namely, shikimic acid, gallic acid, tannic acid, syringic acid, p-coumaric acid, quercetin and kaempferol, was observed from the HPLC chromatogram of the seed extracts of different treatments. We especially emphasized on dietary importance of the pod pericarp, other than seeds, along with their modulation by microbial consortium. The study also highlights the role of beneficial microbes in improving nutritional value by providing protection against oxidative stress. [ABSTRACT FROM AUTHOR]

Abstract: The present study was carried out with the aim of evaluating the effectiveness and potentiality of three compatible rhizosphere microbes, viz., fluorescent Pseudomonas aeruginosa (PHU094), Trichoderma harzianum (THU0816) and Mesorhizobium sp. (RL091), in promoting plant growth and mobilizing phenolic acid biosynthesis in chickpea under challenge of Sclerotium rolfsii. The microbes were applied as seed coating in different combinations in two experimental sets and the pathogen was inoculated after 25 days of sowing in one set. Results revealed that microbe application led to higher growth in chickpea particularly in the triple microbe combination compared to their individual treatments and control. Similarly, pathogen challenged plants accumulated higher amount of phenolic compounds both at the site of attack of the pathogen i.e. collar region as well as leaves compared to unchallenged plants. All the bioagents were found to trigger the level of phenolic compounds at collar region in varying degrees as compared to the healthy control (A). However, the most effective treatment was D7 (combined application of PHU094, THU0816 and RL091 with pathogen challenge) among all the treatments. Shikimic acid was maximally induced amongst all the phenolic compounds. In leaves also, the most effective treatment was D7 where shikimic acid, t-chlorogenic acid, ferulic acid, myricetin, quercetin and syringic acid were produced in higher amounts as compared to treatment B where the plants were challenged only with the pathogen. [Copyright &y& Elsevier]

Abstract: Rhizosphere microbe-mediated induction of antioxidant mechanisms for disease resistance in plants is known but their impact on nutritional content of the edible parts is not clear. A study was conducted to evaluate potentiality of three compatible rhizosphere microbes, viz., fluorescent Pseudomonas (PHU 094), Trichoderma harzianum (THU 0816) and Mesorhizobium sp. (RL 091), singly and in combinations in modulating antioxidants in chickpea edible parts. Total phenolic and flavonoid content, ascorbic acid, free radical and hydroxyl radical scavenging activities as well as reducing power in seeds and pericarp in different microbial combinations were significantly high compared to their single application. However, the triple microbe treatment was most effective in enhancing the antioxidant status of chickpea along with enhanced accumulation of phenolics such as shikimic, gallic, tannic, p-coumaric, and ferulic acids as well as rutin and quercetin. Apart from the triple microbe treatment, dual combination of PHU 094 + THU 0816 also showed potentiality in enhancing the antioxidant and phenolic content majorly in pericarp. These findings suggest that synergistic interaction of microbes in the rhizosphere not only improved the antioxidant level in chickpea seeds but the same were also enhanced in the pericarp which is otherwise considered a waste material. [Copyright &y& Elsevier]

Abstract: The study was conducted to examine efficacy of a rhizospheric microbial consortium comprising of a fluorescent Pseudomonas (PHU094), Trichoderma (THU0816) and Rhizobium (RL091) strain on activation of physiological defense responses in chickpea against biotic stress caused by the collar rot pathogen Sclerotium rolfsii. Results of individual microbes were compared with dual and triple strain mixture treatments with reduced microbial load (1/2 and 1/3rd, respectively, of individual microbial load compared to single microbe application) in the mixtures. Periodical studies revealed maximum activities of phenylalanine ammonia lyase [E.C. 4.1.3.5] and polyphenol oxidase [E.C. 1.14.18.1] and accumulation of total phenol content in chickpea in the triple microbe consortium treated plants challenged with the pathogen compared to the single microbe and dual microbial consortia. Similarly, the expression of the antioxidant enzymes superoxide dismutase [E.C.1.15.1.1] and peroxidase [E.C.1.11.1.7] was also highest in the triple microbial consortium which was correlated with lesser lipid peroxidation in chickpea under the biotic stress. Histochemical staining clearly showed maximum and uniform lignification in vascular bundles of chickpea stem sections treated with the triple microbes. The physiological responses were directly correlated with the mortality rate as least plant mortality was recorded in the triple microbe consortium treated plants. The results thus suggest an augmented elicitation of stress response in chickpea under S. rolfsii stress by the triple microbial consortium in a synergistic manner under reduced microbial load. [Copyright &y& Elsevier]