Responses of Bruguiera sexangula propagules to beneficial microbes in the nursery

Bruguiera sexangula （Lout） Poir., a threatened mangrove tree, was inoculated with beneficial microbes in a nursery to assess any improvements in growth and bio- mass. From soil samples from the rhizosphere of B. sexangula in a mangrove forest in Panangadu of Kerala India, nitrogen-fixing bacteria Azotobacter chroococcum and Azospirillum brasilense were isolated. The phosphatesolubilising bacterium Bacillus megaterium and potassiummobilizing bacteria Frateruria aurantia were also isolated and cultured on suitable media. Later, ripe propagules of B. sexangula were collected from matured trees and raised in sterilized soil bags （13 × 25 cm） containing sterilized soil and sand （2：1 ratio）. The cultured beneficial microbes were propagated and used to inoculate the ripe propagules of B. sexangula and maintained in the nursery for 6 months. After 6 months, growth and biomass of the inoculated propagules were greater than for the uninoculated control propagules. Shoot length, number of leaves, stem girth and root length were also significantly greater than in the controls. This study showed that the mangrove-specific beneficial microbes influenced the growth of B. sexangula

Effects of Organic and Chemical Fertilizations and Microbe Inoculation on Physiology and Growth of Sweet Corn Plants

A pot culture experiment was carried out in a glasshouse to compare the physiology and growth of sweet corn plants (Zea mays L. cv. Honey Bantam) grown under organic and chemical fertilizations with or without microbial inoculation (MI). The organic fertilizer used was fermented mainly using rice bran and oil mill sludge, and the MI was a liquid product containing many beneficial microbes such as lactic acid bacteria, yeast, photosynthetic bacteria and actinomycetes. The application amounts of the organic fertilizer and chemical fertilizers were based on the same rate of nitrogen, phosphorus and potassium. Sweet corn plants fertilized with organic materials inoculated with beneficial microbes grew better than those without inoculation. There were no significant differences in physiology and growth of the sweet corn plants between treatments of chemical fertilizers with and without MI. Among the organic fertilization treatments, only the sweet corn plants with organic fertilizer and MI applied 4 weeks before sowing had similar photosynthetic capacityj total dry matter yield and ear yield to those with chemical fertilizers. Sweet corn plants in other organic fertilization treatments were weaker in physiology and growth than those in chemical fertilization treatments. There was no significant variance among chemical fertilization treatments at different time. It is concluded from this research that this organic fertilizer would be more effective if it was inoculated with the beneficial microbes. Early application of the organic fertilizer with beneficial microbes before sowing was recommended to make the nutrients available before the rapid growth at the early stage and obtain a yield similar to or higher than that with chemical fertilizations.

Mycorrhiza and Phosphate Solubilizing Bacteria:Potential Bioagents for Sustainable Phosphorus Management in Agriculture

Phosphorus(P)is a critical nutrient that plays an essential role in improving soil fertility for optimum plant growth and productivity.It is one of the most deficient macro-nutrients in agricultural soils after nitrogen and is considered inadequate for plant growth and production.To P availability in soils,the farmers are applying huge amounts of synthetic P fertilizers that adversely affect the wider environment,groundwater,soil fertility and microbial population.Many beneficial microbes are known to release and supply soluble P for improving growth and yield of a variety of plants in a sustainable manner in P deficient soils.Thus,inoculation of these microbes,including arbuscular mycorrhizal fungi(AMF)and phosphate solubilizing bacteria(PSB)to soil to enhance crop production without harming the environment,is an alternative approach to chemical fertilizers.The combined role of AMF and PSB in P solubilization is not well understood and the application and mode of action of these microbial groups are often naive due to variation in the environment.Therefore,the current review article would develop a better understanding of the interactive role and mechanisms of AMF and PSB in improving P availability from both organic and inorganic sources in a sustainable crop production system.Finally,the current review would loop out further avenues for researchers interested to commercially produce effective AMF and PSB-based biofertilizers for sustainable management of phosphorus over a wide range of agricultural crops worldwide.

Soil-Plant-Microbe Interactions in Stressed Agriculture Management:A Review

The expected rise in temperature and decreased precipitation owing to climate change and unabated anthropogenic activities add complexity and uncertainty to agro-industry. The impact of soil nutrient imbalance, mismanaged use of chemicals, high temperature, flood or drought, soil salinity, and heavy metal pollutions, with regard to food security, is increasingly being explored worldwide. This review describes the role of soil-plant-microbe interactions along with organic manure in solving stressed agriculture problems. Beneficial microbes associated with plants are known to stimulate plant growth and enhance plant resistance to biotic （diseases） and abiotic （salinity, drought, pollutions, etc.） stresses. The plant growth-promoting rhizobemteria （PGPR） and mycorrhizae, a key component of soil microbiota, could play vital roles in the maintenance of plant fitness and soil health under stressed environments. The application of organic manure as a soil conditioner to stressed soils along with suitable microbial strains could further enhance the plant-microbe associations and increase the crop yield. A combination of plant, stress-tolerant microbe, and organic amendment represents the tripartite association to offer a favourable environment to the proliferation of beneficial rhizosphere microbes that in turn enhance the plant growth performance in disturbed agro-ecosystem. Agriculture land use patterns with the proper exploitation of plant-microbe associations, with compatible beneficial microbial agents, could be one of the most effective strategies in the management of the concerned agriculture lands owing to climate change resilience. However, the association of such microbes with plants for stressed agriculture management still needs to be explored in greater depth.

Microbial enhancement of plant nutrient acquisition

Nutrient availability is a determining factor for crop yield and quality.While fertilization is a major approach for improving plant nutrition,its efficacy can be limited and the production and application of fertilizers frequently bring problems to the environment.A large number of soil microbes are capable of enhancing plant nutrient acquisition and thereby offer environmentally benign solutions to meet the requirements of plant nutrition.Herein we provide summations of how beneficial microbes enhance plant acquisition of macronutrients and micronutrients.We also review recent studies on nutrition-dependent plant-microbe interactions,which highlight the plant’s initiative in establishing or deterring the plant-microbe association.By dissecting complex signaling interactions between microbes within the root microbiome,a greater understanding of microbe-enhanced plant nutrition under specific biotic and abiotic stresses will be possible.