Suseelendra Desai

In Vitro Screening for Abiotic Stress Tolerance in Potent Biocontrol and Plant Growth Promoting Strains of Pseudomonas and Bacillus spp.

Plant growth promoting rhizobacteria (PGPR) has been identified as a group of microbes that are used for plant growth enhancement and biocontrol for management of plant diseases. The inconsistency in performance of these bacteria from laboratory to field conditions is compounded due to the prevailing abiotic stresses in the field. Therefore, selection of bacterial strains with tolerance to abiotic stresses would benefit the end-user by successful establishment of the strain for showing desired effects. In this study we attempted to isolate and identify strains of Bacillus and Pseudomonas spp. with stress tolerance and proven ability to inhibit the growth of potential phytopathogenic fungi. Screening of bacterial strains for high temperature (50°C), salinity (7% NaCl), and drought (-1.2 MPa) showed that stress tolerance was pronounced less in Pseudomonas isolates than in Bacillus strains. The reason behind this could be the formation of endospores by Bacillus isolates. Tolerance to drought was high in Pseudomonas strains than the other two stresses. Three strains, P8, P20 and P21 showed both salinity and temperature tolerance. P59 strain possessed promising antagonistic activity and drought tolerance. The magnitude of antagonism shown by Bacillus isolates was also higher when compared to Pseudomonas strains. To conclude, identification of microbial candidate strains with stress tolerance and other added characteristic features would help the end-user obtain the desired beneficial effects.

Exploiting Plant Growth Promoting Rhizomicroorganisms for Enhanced Crop Productivity

The increasing pressure on land resources has made it imperative for vertical growth through enhanced crop intensity and productivity. To meet this challenge, appropriate integrated nutrient and pest management packages must be configured for different agro-ecological conditions. By 2050, the crop nitrogen demand is expected to reach 40–45 million tonnes. To meet such enormous nitrogen requirements through chemical fertilizers, would not only be expensive but also could severely degrade soil health. Similar is the situation with other macro- and micro-nutrients. The rhizosphere environment, at the interface between root and soil, is a major habitat for soil processes. Rhizosphere biology is approaching a century of investigations, wherein growth-promoting rhizomicroorganisms such as Rhizobium, Azotobacter, Pseudomonas, Bacillus, Azospirillum, Frankia and mycorrhizal fungi have attracted special attention on account of their beneficial activities. Plant growth promoting rhizomicroorganisms (PGPR) include diverse microbes that influence plant health by colonizing roots, enhancing plant growth, reducing plant pathogen populations and activating plant defenses against biotic stresses. PGPRs promote plant growth in different ways such as influencing plant hormonal balance, antagonistic to pathogens through various modes, stimulation of plant resistance/defense mechanisms, effects nutrient uptake by secretion of organic acids or protons to solubilize nutrients, atmospheric N2 fixation and by modifying rhizospheric soil environment by exo-polysaccharides production. Though research was going on in isolation in the above areas, with the advent of a core group for PGPR research, the pace in this direction has significantly increased. The primary emphasis on exploiting the vast biodiversity of microorganisms to identify the beneficial strains has yielded very good results. However, most of the research is yet to reach the end-users. For effective transfer of these technologies, there is a need for functional networking of research, industry and extension systems. In this paper, we describe the recent advances in PGPR research and the future needs to strengthen PGPR research and development that will transfer the benefits to the end-users for enhanced and sustainable farm productivity hence contributing towards food security challenges.

Plant Growth Promoting Pseudomonas spp. from Diverse Agro-Ecosystems of India for Sorghum bicolor

Fluorescent Pseudomonas spp. comprise an important group of rhizosphere bacterial community affecting plant growth. Sorghum is an important fifth largest cereal crop in world. 75 fluorescent Pseudomonas spp. were isolated from diverse agro-ecosystems of India and evaluated for their plant growth promoting ability initially by paper cup method. Fourteen selected isolates were further evaluated under glass house conditions. Plants inoculated with bacteria showed higher growth and nutrient uptake than controls. Seedlings treated with selected isolate P17 showed highest root volume (0.3 cm3 ), shoot length (36.2 cm), dry mass (152 mg), leaf area (31 cm2 ), chlorophyll (23 spad units), carbohydrates (30%), phosphorus (1.3%), nitrogen (2.2%) and other nutrients. Among the evaluated isolates Pseudomonas sp. P17 strain was identified as a potential PGPR for nutrient uptake and plant growth in sorghum. This finding has potential for integrated plant nutrient management in rainfed agroecosystems where farmers tend to rely on cost effective technologies for enhanced profitability

Effect of Polymeric Additives, Adjuvants, Surfactants on Survival, Stability and Plant Growth Promoting Ability of Liquid Bioinoculants

Effect of Polymeric Additives, Adjuvants, Surfactants on Survival, Stability and Plant Growth Promoting Ability of Liquid Bioinoculants The present study was conducted to evaluate the effect of polymeric additives, adjuvant and surfactants for their ability to support growth, shelf-life stability and bio-efficacy of liquid bioinoculants (Bacillus megaterium var. phosphaticum, Azospirilum brasilense and Azotobacter chrococcum). Liquid inoculants formulated with 2% polyvinylpyrollidone (PVP 30 K), 0.1% carboxy methylcellulose (CMC-high density) and 0.025% Polysorbate 20 promoted long-term survival of Bacillus megaterium var. phosphaticum, Azospirillum and Azotobacter with 5.6 x 107, 1.9x108 and 3.5x107 cfu ml-1, respectively after 480 days of formulation when stored at 30oC.

Application of Microbiology in Dryland Agriculture

Microorganisms are key players in nutrient cycling and hence form important components of a soil ecosystem. Besides, improving nutrient availability, certain microorganisms also provide growth and health benefits to plants through direct and indirect mechanisms. Dryland soils are are poorly developed with low organic matter content and hence have poor water retention capacity. Besides, dryland soils face various abiotic stresses like nutrient imbalance, drought, heat etc. Application of organic based fertilizers improves the microbial populations and soil organic carbon. Cropping systems and residue management practices also influence microbial parameters in dryland soils. Increased abundance of microorganisms in dryland soil can help in improving soil aggregation and soil organic matter carbon content, thus increasing the water retention capacity of the soil. Besides, microbial inoculants with specific function such as nutrient solubilization and mobilization, plant growth promotion, disease control and abiotic stress management can be applied alone or in combination. Thus, the promotion of microbial-based technologies and/or the management practices that improve soil microbial parameters is important for the sustainability of dryland ecosystems.

Exploiting PGPR and AMF Biodiversity for Plant Health Management

Indian subcontinent is one of the mega hotspots for biodiversity including microbes. So far, only very little microbial diversity has been harnessed for human and animal welfare. The importance of soil microorganisms in plant health management is well known. The interaction between bacteria and plant roots may be beneficial, harmful, or neutral for the plant, and sometimes the effect of a particular organism may vary as the soil conditions change. Among the diverse range of plant growth-promoting rhizobacteria (PGPR) identified, bacterial species such as Pseudomonas and Bacillus spp. have a wide distribution. The mechanisms by which PGPR enhance plant growth include plant growth promoters, resistance inducers, biochemicals, etc. The nitrogen-fixing bacteria are known to enhance growth of plants by means of symbiotic or free-living association with plants. Arbuscular mycorrhizal fungi (AMF) enhancing plant growth has been reported by several workers. These microbes could be inoculated either singly or in combinations to deliver maximum benefits to the plants. For instance, combined inoculation of AMF with other PGPR exerted positive effects on the growth of several crop plants. By exploiting the microbial biodiversity, the input cost in agricultural production systems could be reduced considerably and thereby make agriculture a sustainable venture especially for small and marginal farmers whose resources are limited. Microbes can supplement nutrients to the plants, induce resistance against biotic and abiotic stresses, protect from insect pests and plant pathogens, manage weeds and nematodes, etc. In this chapter, the rich microbial biodiversity, its systematic characterization, cataloguing, and evaluation for improving agricultural production in an economical and eco-friendly way have been discussed.

Seed Bacterization with Fluorescent Pseudomonas spp. Enhances Nutrient Uptake and Growth of Cajanus cajan L.

Among plant-growth-promoting rhizobacteria (PGPR), fluorescent Pseudomonas spp. are an important group affecting plant growth. Pigeon pea is an important pulse crop and most of the studies were aimed at using Pseudomonas spp. for pest management in pigeon pea. Seventy-five fluorescent Pseudomonas spp. were isolated from diverse agroecosystems of India and evaluated for their plant-growth-promoting ability, primarily by the paper cup method. Seventeen selected isolates were further evaluated by short-term pot assay for plant growth promotion. Seeds treated with bacteria showed greater nutrient concentration and growth than the control. Isolate P17 showed significant growth promotion in terms of root length (54.5 cm), dry mass (323 mg), chlorophyll (24 spad units), carbohydrates (21.2 percent), nitrogen (2.45 percent), calcium (1.82 percent), iron (984 ppm), and manganese (564 ppm). Pseudomonas sp. P17 strain was identified as a potential PGPR for nutrient uptake and plant growth promotion in pigeon pea, and this finding paves a way for integrated plant nutrient management in rainfed agroecosystems.

In vitro Characterization of Trichoderma viride for Abiotic Stress Tolerance and Field Evaluation against Root Rot Disease in Vigna mungo L.Leo Daniel

Soil-borne phytopathogenic fungi pose serious threats to yield of several crops. Biological control is an ecofriendly approach in the effective management of crop diseases. Trichoderma viride is an important soil-borne fungus, which play an important role in antagonism by secretion of different hydrolytic enzymes. Black gram is an important pulse crop world-wide and its yield is severely affected by Macrophomina root rot. Abiotic stresses greatly influence the performance of biocontrol agents. T. viride was evaluated for its In vitro abiotic stress tolerance ability and its field bioefficacy against root rot disease in blackgram. Growth of T. viride decreased with increasing in salinity, temperature and drought. T. viride effectively inhibited the growth of R. solani (45%) and M. phaseolina (40%) under In vitro conditions. T. viride was compatible with 0.25% mancozeb, 1.0% copper oxy chloride and metalaxyl. Among three doses, plants treated with 6 g.kg-1 of T. viride showed highest yield of 1375 kg.ha-1 and lowest root rot incidence of 14.77% which were statistically on par with 4 g.kg-1 T. viride treated plants. To conclude, this study identified an abiotic stress tolerant T. viride for effective management of root rot disease and enhanced yield of Vigna mungo when applied as seed dresser at a concentration of 4g kg-1 under field conditions.