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Potassium (K) availability is a major problem in tea growing soils of Assam, North-east India. The present investigation aims at the isolation of potash mobilizing microorganisms in the tea soil and evaluation of their potential in increasing available potash under in vitro. Ten numbers of potash mobilizing bacteria (KMB) were isolated from the experimental tea estate of Tocklai Tea Research Institute (TTRI), using a serial dilution plate method on modified GYCaA media. The isolates were characterized based on their cultural and morphological characteristics. On screening the isolates, it was found that TKMB11 was significantly superior in mobilizing soil K; followed by TKMB6, TKMB3 and TKMB8 in same order in efficiency. The present investigation indicates that the application of KMB might serve as a cost-effective and alternate viable technology to mobilize insoluble K-source in tea soil for sustainable crop improvement.

Tea [Camellia sinensis (L.) O. Kunze] is an aromatic beverage yielding perennial plant. The manufactured tea is commonly prepared by pouring hot or boiling water over cured leaves of the Camellia sinensis, an evergreen shrub native to Asia. After water, it records the most widely consumed drink all over the world. India is the second largest producer of tea in the world after China, including the famous Assam tea and Darjeeling tea. However, as the Indian subcontinent is mostly rain fed and the cropping season also needs a moist climate with alternating wet and dry periods, the micro-climate prevailing the region is, thus, prune for the establishment of major tea pathogens like Fusarium solani, responsible for Fusarium die-back disease. Present findings illustrated the impact of an incubation period of 60 days for maximum decomposition (up to 17.4% over untreated control) of the Fusarium treated tea twigs. Nectria formation after 60 days of incubation and softening of stem tissue indicated the decomposition of the fungus treated twigs due to the prominent growth of F. solani. Three replicates were maintained at each case and all the data were statistically designed.

crop, extensively cultivated in Assam, North-East India. Exploitation and conservation of tea soil microflora is important in minimizing the use of toxic chemicals since the later is known for its adverse effect on natural environment. Isolation and exploitation of microbial resources of native tea growing soil are important mainly due to their immense potentiality in maintenance of biogeochemical cycles, promotion of plant growth, inhibition of destructive pests and pathogens etc. Quantitative as well as qualitative distribution of microbes in tea plantations of Assam, N. E. India, in the context of their geographical position and geological and geochemical habitats are need to be worked out, since there is scarce information concurrently on the spatial and temporal patterns of microbial diversity and distribution patterns in tea ecosystem by constructing maps. Geographic information system (GIS) is useful in this regard to strengthen the microbial resource management strategies in tea.

Allelopathic compounds are considered as growth and germination indicators. The present investi gation elucidates the impact of caffeine as an allelopathic substance reducing the growth and biomass production and inhibiting the germination of popular tea weed, Borreria hispida L. seeds. Seed treatment of tea weed, Borreria hispida L. with different concentrations of caffeine indicated delay in germination start for a longer period of time. The growth and germination of Borreria hispida L. seeds were affected maximum at caffeine concentrations of high dose. The seedlings of the Borreria hispida L. had also an abnormal growth and twisted form after exposed to caffeine. The study also revealed negative impacts of caffeine at its maximum dose (1000 ppm) on Borerria hispida L. showing a reduction of plant height by 11.1 cm against control. The study, thus, provides evidence of allelopathic syndrome in tea eco-system. This is the first report evaluating the caffeine allelopathy influencing the growth and germination to popular tea weed, Borreria hispida L.

Microbial contamination, distribution pattern, population density of microorganism in tea infusion prepared from 262 black tea samples were analysed consecutively for a period of seven years from 2011 to 2017. Surprisingly, most of the tea samples were contaminated with various microorganisms like E. coli, Salmonella sp., molds etc. Tea samples were received from tea estates of Upper Assam, South Bank and North Bank regions predominantly in peak growing season (summer) and in back end crop (winter season). The standard plate count (SPC) technique was followed to assess the microbial load such as total plate count (TPC), yeast and mold populations and intestinal enterobacteria like Escherichia coli and Salmonella sp. Intestinal microorganism, E. coli and Salmonella sp. were not detected in any of the tea samples of the three regions till 2015 whereas mold population and other microbes were abundant on total plate count. Contamination of E. coli and Salmonella sp. was detected along with other microorganisms in the tea samples analysed during 2016 and 2017. However, the per cent distribution of E.coli was the least while total plate count was highest followed by mold and Salmonella sp. Contamination of black tea may occurs from various sources like field contaminated tea leaves, careless handling of tea leaves in field and trough house, use of contaminated water for washing machineries and factory floor, roaming of so many workers in and around the factory premises etc. The growth of microorganisms in those areas is also induced by conductive atmosphere like temperature and high humidity. Therefore, multiple efforts are necessary to keep the made tea contamination free.

In the present investigation, an attempt was made to assess the compatibility of seven biopesticides such as Aspergillus niger (Identification code; MM/PSM/10), Azospirillum brasilense (Identification code; MM/AZM/ 10), Bacillus subtilis (MTCC121), Beauveria bassiana (MTCC984), Trichoderma harzianum (IMI356100), Trichoderma viride (IMI356099), Verticillium lecanii (MTCC956), isolated from the native tea ecosystem, against twenty five agrochemicals using a novel approach. The results indicated the ability of A. niger and T. harzianum to emulate in association with all the agrochemicals tested in vitro. The compatibility shown by some of the biopesticides against the agrochemicals suggests their selective substantiation to cope with the integration of chemical supplements

Live wood eating termites are responsible for considerable damage to young and mature teas throughout North-East India. Termite infestation leads not only to economic loss but also to the failure of several years of effort to grow tea plants. This study reveals the efficacy of various non-chemical approaches to control the termite problem in Assam tea plantation. Two multipli cation field trials consisted of twelve non-chemical treatments were conducted following randomized block design (RBD) with three replications. The trials revealed that Metarhizium anisopliae, Beauveria bassiana, Heterorhabditis indica and Ipomea carnea were effective in controlling the termites in tea compared to the check (thiamethoxam, a commonly used chemical pesticide against termites in conventional tea estates) as well as to control (untreated- water spray for both organic and conven tional tea estates). Along with these non-chemical treatments, an integrated management package for termite control is discussed

The adoption of biological techniques for sustainable tea cultivation is a pertinent strategy for an efficient and ideal agricultural growth with minimal generation of adverse environmental impacts that may affect water resources, ecosystems or the quality of human life. Modern agriculture offers immense opportunity to exploit beneficial soil microbial resources such as nitrogen fixers, phosphate solubilizers, potash mobilizers, cellulose degraders, AM fungi, etc., as well as biopesticides (microbial biocontrol agents and entomopathogens), to optimize crop benefit and maintain soil quality. According to Raja (2013) there is a rising trend towards organic agriculture using biological-based organics as an alternative to agrochemicals. Organic farming ensures food safety as well as aiding biodiversity conservation and functioning in the soil. It is highly likely to be dependent on the native soil microflora which constitutes all kinds of useful bacteria and fungi including the AMF and PGPR. A synergistic interaction of PGPR and AMF is recorded as highly suitable to fertilizer use patterns in agricultural soil. An enhanced plant nutrient-use efficiency with PGPR and AMF in an integrated nutrient management system has been achieved by Adesemoye et al. (2008), and thereby suggested the application of microbes with reduced doses of fertilizer in agricultural soil. Microbial inoculants are of paramount significance in integrated nutrient and pest management schedules and thereby assist in the generation of healthy agricultural practices (Adesemoye and Kloepper, 2009). Microbial biofertilizers and biopesticides fulfil diverse beneficial interactions in tea soil and thereby lead to promising solutions for sustainability. As the rhizosphere is an ideal habitat for the isolation of beneficial microorganisms (Mendes et al., 2013), considerable effort has been made to explore the microbial diversity of the surface and sub-surface soil of tea plants under cultivation in diverse topographical regions. Different species of microbial inoculants are now known to antagonize tea pathogens via mycoparasitism, producing volatile and non-volatile antibiotics, competing for nutrients and space, as well as their diverse beneficial activities contributing towards enhanced crop production. The use of microbials such as viruses (NPV/GV), spore-forming bacteria (Bacillus strains) and fungi (Beauveria, Metarhizium, Verticillium, Paecilomyces), holds great promise in this regard. Most of the tea estates, however, refrain from risking crop loss due to pest attack and liberally use synthetic pesticides under ‘no threshold category of pest management’ (Pedigo, 2002), and as microbial insecticides are pest specific, the potential market for these products is rather limited.

The aim of this study was to optimize cultural conditions for optimum growth and bioactive metabolite production by Aspergillus strain TSF 146, isolated from the subsurface soils of Brahmaputra plains, Assam, India. Agar disc diffusion assay was used to examine the antagonistic activity of the strain. The effect of different culture media, temperature, pH, incubation period, shaking, inoculum size and various carbon and nitrogen sources on the mycelial growth and bioactive metabolite production in a fixed volume of culture broth were studied. Aspergillus strain TSF 146 grew well and produced optimum bioactive metabolites in Potato dextrose broth medium at 25 °C on the 14th day of the incubation. The optimal mycelial growth, however, was obtained at pH 5.5. Sucrose (2.0 g/l) and asparagine (1.0 g/l) were the best carbon and nitrogen sources respectively for optimum growth and production of active metabolites by the isolate. Inoculum size of 2x1010 spores/ml with periodic shaking at 150 rpm optimized production of bioactive molecules. The results of the present investigation indicated that cultural conditions like carbon, nitrogen and mineral sources as well as physical factors such as temperature, pH, incubation period, inoculum size and shaking greatly affected the growth and production of bioactive metabolites by Aspergillus strain TSF 146.

Soil microflora was isolated by serial dilution plate method using different culture media. The highest fungal population was recorded in spring at the topsoil (1–9 cm), and decreased in other seasons with increasing depths. Twenty-one fungal species belonging to 14 genera were recovered from all depths throughout the seasons with the highest population and relative abundance of Aspergillus flavus (8.4%), followed by Penicillium chrysogenum (8.0%) and lowest by Rhizopus oryzae, R. nodosus and Trichophyton sp. (2.8% each). Phycomycetes (80.1%) were dominant in the study site followed by Zygomycetes (14.1%), Ascomycetes (3.7%) and sterile mycelia (2.1%). Soil pH, moisture content, organic C (Corg), total N concentration (Ntot) and available K had positive correlations (p<0.05 and <0.01) with the fungal colony forming unit. Difference in soil depth and seasonal variation have an influence on the microfungal population numbers as well as their species composition in Nameri forest soil.