Effect of inoculation of Zea mays with Azospirillum brasilense strains under temperate conditions

Evaluating the use of plant hormones and biostimulators in forage pastures to enhance shoot dry biomass production by perennial ryegrass (Lolium perenne L.)

Fertilisation of established perennial ryegrass forage pastures with nitrogen (N)-based fertilisers is currently the most common practice used on farms to increase pasture forage biomass yield. However, over-fertilisation can lead to undesired environmental impacts, including nitrate leaching into waterways and increased gaseous emissions of ammonia and nitrous oxide to the atmosphere. Additionally, there is growing interest from pastoral farmers to adopt methods for increasing pasture dry matter yield which use 'natural', environmentally safe plant growth stimulators, together with N-based fertilisers. Such plant growth stimulators include plant hormones and plant growth promotive microorganisms such as bacteria and fungi ('biostimulators', which may produce plant growth-inducing hormones), as well as extracts of seaweed (marine algae). This review presents examples and discusses current uses of plant hormones and biostimulators, applied alone or together with N-based fertilisers, to enhance shoot dry matter yield of forage pasture species, with an emphasis on perennial ryegrass.

Integrated plant nutrient system - with special emphasis on mineral nutriton and biofertilizers for Black pepper and cardamom - A review

Integrated Plant Nutrition System (IPNS) as a concept and farm management strategy embraces and transcends from single season crop fertilization efforts to planning and management of plant nutrients in crop rotations and farming systems on a long-term basis for enhanced productivity, profitability and sustainability. It is estimated that about two-thirds of the required increase in crop production in developing countries will have to come from yield increases from lands already under cultivation. IPNS enhances soil productivity through a balanced use of soil nutrients, chemical fertilizers, combined with organic sources of plant nutrients, including bio-inoculants and nutrient transfer through agro-forestry systems and has adaptation to farming systems in both irrigated and rainfed agriculture. Horticultural crops, mainly plantation crops, management practices include application of fertilizers and pesticides which become inevitable due to the depletion of soil organic matter and incidence of pests and diseases. The extensive use of chemical fertilizers in these crops deteriorated soil health that in turn affected the productivity. To revitalize soil health and to enhance productivity, it is inexorable to enrich the soil using microorganisms. The lacunae observed here is the lack of exploitation of indigenous microbes having the potential to fix atmospheric nitrogen (N) and to solubilize Phosphorus (P) and Potassium (K). The concept of biofertilizer application appears to be technically simple and financially feasible, but the task of developing biofertilizers with efficient strains in appropriate combinations in a consortia mode is not easier. More than developing consortia, a suitable delivery system to discharge the microbial inoculants warranted much effort. This review focuses on the integrated plant nutrition system incorporating biofertilizer with special emphasis on developing and formulating biofertilizer consortium.

Intact Soil-Core Microcosms for Evaluating the Fate and Ecological Impact of the Release of Genetically Engineered Microorganisms

Intact soil-core microcosms were studied to determine their applicability for evaluating the transport, survival, and potential ecosystem effects of genetically engineered microorganisms before they are released into the environment. Soil-core microcosms were planted with wheat and maize seeds and inoculated with Azospirillum lipoferum SpBr17 and SpRG20a Tn 5 mutants, respectively. Microcosm leachate, rhizosphere soil, plant endorhizosphere, insects, and xylem exudate were sampled for A. lipoferum Tn 5 mutant populations. A. lipoferum Tn 5 populations, determined by most-probable-number technique-DNA hybridization, varied from below detection to 10 6 g of dry root −1 in the rhizosphere, with smaller populations detected in the endorhizosphere. Intact soil-core microcosms were found to maintain some of the complexities of the natural ecosystem and should be particularly useful for initial evaluations of the fate of plant-associated genetically engineered bacteria.

Cyst production and brown pigment formation in aging cultures of Azospirillum brasilense ATCC 29145

Encystation in Azospirillum brasilense ATCC 29145 was observed by using routine laboratory staining and phase-contrast and electron microscopy. Encystment occurred in liquid and in solid or semisolid media containing fructose (8 mM) and KNO3 (0.5 mM). The encysted forms consisted of a central body filled with poly-beta-hydroxybutyric acid granules, an electron-transparent intinelike region, and a thick outer layer. Enlarged giant encysted forms with multiple central bodies were also observed during the germination of a desiccated brown colony. Morphogenetically different forms in an aging culture could be resolved by sucrose density gradient centrifugation. The dense encysted forms along with numerous granules in a fibrillar network pelleted at 70% sucrose, while empty saclike envelopes along with vegetative cells and coccoid bodies pelleted at 55% sucrose. Different media induced various degrees of pigmentation in A. brasilense ATCC 29145 after aging. The pigment possessed several of the properties reported for microbial melanins, including insolubility in water and organic solvents, solubility in cold and hot alkali, and bleaching in hydrogen peroxide. The UV absorption maxima of the alkali extract were at 280 and 310 nm. Electron micrographs of the brown pigment showed that it occurred as aggregated granules surrounding the encysting cells as well as being excreted into the medium in an aging culture. It is concluded that A. brasilense ATCC 29145 produces compounds that form a brown pigment similar to melanin and are expressed under the influence of certain cultural conditions conducive for encystment.