Microbial inoculants to support tea industry in India

13-19A long term study has been carried out for over a decade across various tea gardens, located in different parts of Indian Himalayan Region (IHR), with a focus on rhizosphere microbiology of tea. Occurrence of ‘negative rhizosphere effect’ exerted by the established tea bushes, in contrast to the normal stimulatory effect exhibited by the plants in general as well as young tea bushes, is the first and foremost feature associated with tea plants. Colonization by large populations of antagonists and lowering of the soil pH are the other important characteristics associated with tea rhizosphere. With a view of scaling down the use of chemical fertilizers, experiments were conducted on isolation, characterization and formulation of suitable microbial inoculants for use in tea plantations across hilly regions. Based on a number of attributes related to plant growth promotion and disease control, selected bacterial and mycorrhizal species have been developed in suitable formulations for application in tea plantations. The post-application observations indicated the benefits of microbial inoculations on seed, cutting and tissue culture raised tea plants. The present paper is an attempt to review the basic and applied research work carried out on rhizosphere microbiology of tea, particularly in the last two decades, with reference to possible application in the tea industry. </span

In vitro evaluation of antagonistic properties of Pseudomonas corrugata

Pseudomonas corrugata, a soil bacterium originally isolated from a temperate site of Indian Himalayan Region (IHR) is examined for its antagonistic activities against two phytopathogenic fungi, Alternaria alternata and Fusarium oxysporum. Although the bacterium did not show inhibition zones due to production of diffusible antifungal metabolites, a reduction in growth between 58% and 49% in both test fungi, A. alternata and F. oxysporum, was observed in sealed Petri plates after 120 h of incubation due to production of volatile antifungal metabolites. Reduction in biomass of A. alternata (93.8%) and F. oxysporum (76.9%) in Kings B broth was recorded after 48 h of incubation in dual culture. The antagonism was observed to be affected by growth medium, pH and temperature. The reduction in fungal biomass due to antagonism of bacteria was recorded maximum in the middle of the stationary phase after 21 h of inoculation. The production of siderophore, ammonia, lipase and chitinase in growth medium by P. corrugata were considered contributing to the antagonistic activities of the bacterium

<span style="font-size:12.0pt;font-family:"Times New Roman";mso-bidi-font-weight: bold" lang="EN-US">Effect of Temperature on Solubilization of Tricalcium Phosphate by <i>Pseudomonas corrugata</i> </span>

457-460Pseudomonas corrugata, a soil isolate, initially obtained from a temperate location in Sikkim (Himalaya), was examined for its tricalcium phosphate solubilizing ability along a wide temperature range, from psychrophillic to mesophillic. The phosphate solubilization, by indirect petridish assay, was in conformity with the results of direct estimation of phosphate solubilization in broth. While the maximum solubilization was found to occur at 21°C, the bacteria solubilized more phosphate at 4°C than at 28°C. The species showed affinity towards lower temperature range. The study has implications for developing carrier-based microbial inoculants for improved growth of plants in the mountains

Characterization of a phosphate solubilizing and antagonistic strain of Pseudomonas putida (B0) isolated from a sub-alpine location in the Indian Central Himalaya

The morphological, biochemical, and physiological characteristics of a phosphate solubilizing and antagonistic bacterial strain, designated as B0, isolated from a sub-alpine Himalayan forest site have been described. The isolate is gram negative, rod shaped, 0.8 × 1.6 μm in size, and psychrotrophic in nature that could grow from 0 to 35°C (optimum temp. 25°C). It exhibited tolerance to a wide pH range (3-12; optimum 8.0) and salt concentration up to 4% (w/v). Although it was sensitive to kanamycin, gentamicin, and streptomycin (1000 μg mL-1). The isolate showed maximum similarity with Pseudomonas putida based on 16S rRNA analysis. It solubilized tricalcium phosphate under in vitro conditions. The phosphate solubilization was estimated along a temperature range (4-28°C), and maximum activity (247 μg mL -1) was recorded at 21°C after 15 days of incubation. The phosphate solubilizing activity coincided with a concomitant decrease in pH of the medium. The isolate also exhibited antifungal activity against phytopathogenic fungi in Petri dish assays and produced chitinase, β-l,3-glucanase, salicylic acid, siderophore, and hydrogen cyanide. The plant growth promotion and antifungal properties were demonstrated through a maize-based bioassay under greenhouse conditions. Although the bacterial inoculation was found to result in significant increment in plant biomass, it stimulated bacterial and suppressed fungal counts in the rhizosphere. The present study is important with respect to enumerating microbial diversity of the colder regions as well as understanding the potential biotechnological applications of native microbes