Bacillus megaterium DE BARY TRS-4 was isolated from tea rhizosphere and tested for its ability to promote growth and cause disease reduction in tea plants. In vivo studies revealed the ability of this bacterium to promote growth of tea plants very significantly. Brown root rot disease, caused by Fomes lamaoensis was markedly reduced by application of the bacterium to the soil. Population of F. lamaoensis in soil before and after application of B. megaterium, as determined by ELISA and dot-blot using PAb raised against the pathogen, was shown to be greatly reduced in presence of the bacterium. Biochemical changes induced in tea plants were also examined. Root colonization by B. megaterium and subsequent inoculation with F. lamaoensis also led to an increase in polyphenolics, as well as in defense related enzymes-peroxidase, chitinase, beta -1,3-glucanase and phenyl alanine ammonia lyase. Determination of mechanism of action of this bacterium revealed it to be able to solubilize phosphate, produce IAA, siderophore and antifungal metabolite. The plant growth promotion and reduction of disease intensity have been shown to be due to a combination of several mechanisms.

Soil microorganisms with potential for alleviation of abiotic stresses in combination with plant growth promotion would be extremely useful tools in sustainable agriculture. To this end, the present study was initiated where forty-five salt tolerant bacterial isolates with ability to grow in high salt medium were obtained from the rhizosphere of Triticum aestivum and Imperata cylindrica. These bacteria were tested for plant-growth-promoting rhizobacteria traits in vitro such as phosphate solubilization, siderophore, ACC deaminase and IAA production. Of the forty-five isolates, W10 from wheat rhizosphere and IP8 from blady grass rhizosphere, which tested positive in all the tests were identified by morpholological, biochemical and 16SrDNA sequencing as Bacillus safensis and Ochrobactrum pseudogregnonense respectively and selected for in vivo studies. Both the bacteria could promote growth in six varieties of wheat tested in terms of increase in root and shoot biomass, height of plants, yield, as well as increase in chlorophyll content. Besides, the wheat plants could withstand water stress more efficiently in presence of the bacteria as indicated by delay in appearance of wilting symptoms increases in relative water content of treated water stressed plants in comparison to untreated stressed ones, and elevated antioxidant responses. Enhanced antioxidant responses were evident as elevated activities of enzymes such as catalase, peroxidase, ascorbate peroxidase, superoxide dismutase and glutathione reductase as well as increased accumulation of antioxidants such as carotenoids and ascorbate. Results clearly indicate that the ability of wheat plants to withstand water stress is enhanced by application of these bacteria which also function as plant growth promoting rhizobacteria.

Five varieties of wheat (Triticum aestivum L.) -KW, UP 2752, PBW 343, SO and LV -were subjected to water stress and sampling was done on the 3 rd , 6 th and 9 th day of stress. RWC decline in KW, UP 2752 and PBW 343 (36.65, 42.34 and 40.75% respectively) was comparatively lesser than in LV and SO (52.93 and 52.67% respectively). In all varieties tested, three antioxidant enzymes (POX, APOX and GR) showed an initial increase. The activity of POX and GR increased with the increase in the duration of stress in KW, UP 2752 and PBW 343, while the activity of APOX declined. However, CAT and SOD showed an initial increase in these varieties, whereas it declined in SO and LV with increase in the period of stress. Accumulation of H 2 O 2 declined during prolonged water stress in KW, UP 2752 and PBW 343, while it increased in LV and SO. The accumulation of MDA content was three times higher in susceptible varieties than in tolerant varieties. The content of proline, phenol and ascorbate increased during water stress whereas the accumulation of carotenoid showed a significant decrease after showing an initial increase in the tested varieties. Higher values of total antioxidant and MSI were recorded in KW, UP 2752 and PBW 343 during stress while after 6 days MSI declined in LV and SO. During water stress there was a general decline in the total chlorophyll content. Analyzing the data, the present work suggested that out of the five varieties, KW, UP 2752 and PBW 343 showed more tolerance to water stress than SO and LV.Keywords: antioxidants, carotenoids, drought, lipid peroxidation.Abbreviations: APOX: ascorbate peroxidase (EC.1.11.1.11); CAT: catalase (EC.1.11.1.6); CMS: cell membrane stability; DAB: diaminobenzidine; EC: electrical conductivity; GR: glutathione reductase (EC 1.6.4.2); H 2 O 2 : hydrogen peroxide; KW: Kaweri; LV: local variety; MDA: malondialdehyde; MSI: membrane stability index; NBT: nitro blue tetrazolium; PPO: polyphenol oxidase; POX: peroxidase (EC. 1.11.17); RH: relative humidity; ROS: reactive oxygen species; RWC: relative water content; SO: Sonalika; SOD: superoxide dismutase (EC 1.15.1.1); TBA: thiobarbituric acid; TCA: trichloroacetic acid.Oxidative stress in five wheat varieties (Triticum aestivum L.) exposed to water stress and study of their antioxidant enzyme defense system, water stress responsive metabolites and H 2 O 2 accumulation

Aim:  To evaluate Ochrobactrum anthropi TRS‐2 isolated from tea rhizosphere and its talc based formulation for growth promotion and management of brown root rot disease of tea. Methods and Results:  Ochrobactrum anthropi TRS‐2, isolated from tea rhizosphere could solubilize phosphate, produce siderophore and IAA in vitro and also exhibited antifungal activity against six test pathogens. Application of an aqueous suspension of O. anthropi to the rhizosphere of nursery grown tea seedlings of five varieties of tea (TV‐18, T‐17, HV‐39, S‐449, UP‐3 and) led to enhanced growth of the treated plants, as evidenced by increase in height, in the number of shoots and number of leaves per shoot. Treatment with O. anthropi also decreased brown root rot of tea, caused by Phellinus noxius. Multifold increase in activities of chitinase, β‐1,3‐glucanase, peroxidase and phenylalanine ammonia lyase in tea plants was observed on application of O. anthropi to soil followed by inoculation with P. noxius. A concomitant increase in accumulation of phenolics was also obtained. Further, talc based formulation of O. anthropi was prepared and its survival determined every month up to a period of 12 months. Ochrobactrum anthropi could survive in the formulation up to a period of 9 months with a concentration of 7·0 log10 CFU g−1, after which there was a decline. Talc formulation was as effective as aqueous suspensions in both plant growth promotion and disease suppression. Conclusion:  Ochrobactrum anthropi, either in aqueous suspension or as talc formulation induced growth of tea plants and suppressed brown root rot disease. It induced defense responses in tea plants. Significance and Impact of the Study:  Ochrobactrum anthropi and its talc based formulation can be considered as an addition to available plant growth promoting rhizobacteria (PGPR) currently being used for field application. The present study offers a scope of utilizing this bacterium for growth promotion and disease management which would help in reduction of the use of chemicals in tea plantations.

Six varieties of lentil (Lens culinaris Medik.) Á Asha, Subrata, IPL 406, IPL 81, Lv and Sehore Á were exposed to temperatures ranging from 30Á508C which resulted in retarded germination and seedling growth at higher temperatures. Tolerance index and membrane stability tests revealed Sehore and Lv to be susceptible to elevated temperatures while IPL 406, IPL 81, Asha and Subrata were tolerant. Catalase, ascorbate peroxidase and superoxide dismutase showed an initial increase before declining at 508C, while peroxidase and glutathione reductase activities declined at all temperatures. Lipid peroxidation significantly increased in all varieties. In the tolerant varieties, there was an initial decrease in accumulation of H 2 O 2 followed by an increase from 408C onwards; however, in the susceptible varieties, accumulation was enhanced at all high temperatures. Ascorbate and glutathione also showed initial increase followed by a decline. Total antioxidant activity was at a maximum at 35Á408C in the tolerant varieties and at 308C in the susceptible ones. Oxidative stress induced by high temperature was ameliorated by treatment with salicylic acid, abscisic acid or CaCl 2 , of which salicylic acid was the most effective.

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A total of 18 bacterial isolates were obtained from the rhizosphere of Sechium edule growing in the lower foothills of Darjeeling, India. The bacterial isolates were tested for PGPR traits in vitro such as phosphate solubilization, HCN, siderophore, IAA, chitinase, protease production as well as inhibition of pthytopathogens. Of all the bacterial isolates, one bacterium designated as BRHS/S-73 was found to possess all the tested characters which was identified on the basis of 16S rRNA gene sequence analysis as Bacillus altitudinis and was selected for in vivo studies. A significant improvement in growth measured in terms of increase in root length, shoot length, and increase in root and shoot biomass was observed when seeds of Vigna radiata, Cicer arietinum, and Glycine max were bacterized prior to sowing in field condition. Besides, the bacterium could also solubilize soil phosphate. Apart form growth promotion, root rot disease of Vigna radiata caused by Thanatephorus cucumeris was also significantly reduced by 74% when the bacterium was applied to the rhizosphere prior to pathogen challenge. The biocontrol efficacy of the bacterium was found to be 66.6% even after 30 days of pathogen inoculation. Activities of key defense related enzymes such as phenylalanine ammonia lyase, peroxidase, β-1,3-glucanase, and chitinase in both roots and leaves of treated plants were also enhanced. Results clearly suggest that B. altitudinis (BRHS/S-73) is a potential PGPR which can be used as efficient microorganism for enhancement of plant growth and suppression of fungal disease.

Bacterization of soybean seeds or roots with Rhizobium japonicum significantly reduced charcoal rot disease caused by Macrophomina phaseolina . Rhizobium japonicum inhibited the growth of M. phaseolina on both liquid and solid media. Replacement of nutrient medium with culture filtrate of R. japonicum significantly reduced mycelial growth of M. phaseolina . Whole culture extracts of R. japonicum yielded a toxic substance which was identified as rhizobitoxine after chromatographic, ultraviolet, and infrared spectrophotometric analyses. This compound also was detected in the roots of soybean inoculated with either R. japonicum alone or in combination of R. japonicum and M. phaseolina . Dosage response curves with rhizobitoxine showed it to be antifungal. The possible role of rhizobitoxine in protecting soybean roots from M. phaseolina infection is discussed.