Deciphering the Mechanisms of Microbe Mediated Drought Stress Alleviation in Wheat

Drought stress adversely influences the crop plants. Herein, present research was designed to elucidate the role of plant growth promoting microbes for amelioration of water stress in wheat. A pot experiment was conducted for screening the microorganisms on the basis of plant growth, chlorophyll and proline content under water stress. Bacillus sp. BT3 and Klebsiella sp. HA9 were found more promising strains that positively influenced the plant growth, chlorophyll and proline status of seedlings under water stress condition. Further, Bacillus sp. BT-3 and Klebsiella sp. HA9 along with check strain (BioNPK) were used for elucidating their detailed effect on morphological, biochemical, physiological and molecular traits to mitigate drought stress in wheat. Microbial inoculation significantly enhanced plant growth, biomass, relative water content, chlorophyll content and root morphological parameters over the uninoculated water stressed (30% FC) control. Likewise, sugar content, protein content and antioxidant enzymes were also significantly enhanced due to microbial inoculation under water stress (30% FC). Microbial inoculation significantly decreased proline, glycine betaine, lipid peroxidation, peroxide and superoxide radicals in wheat over the uninoculated water stressed (30%FC) control. Quantitative real-time (qRT)- PCR analysis revealed that Bacillus sp. BT-3, Klebsiella sp. HA9 and BioNPK inoculation significantly upregulated stress responsive genes (DHN, DREB, L15 and TaABA-8OH) over the uninoculated water stressed (30% F.C.) control. The study reports the potential of Bacillus sp. BT3 and Klebsiella sp. HA9 along with BioNPK in water stress alleviation in wheat which could be recommended as effective biofertilizers.

Biotecnologia microbiana: inoculação, mecanismos de ação e benefícios às plantas

O uso de microrganismos está sendo aderido globalmente como uma alternativa biotecnológica para otimizar a produtividade vegetal de forma sustentável, atenuando o uso de produtos químicos e os impactos ambientais. Inoculantes microbianos, como as rizobactérias (Plant growth-promoting rizhobacteria - PGPR), micorrizas e fungos, combinados ou separados, podem ser inoculados em sementes, raízes, solo ou folhas. Microrganismos promotores do crescimento de plantas (Plant growth-promoting microbes - PGPM) atuam de forma direta como bioestimulantes e biofertilizantes; e de forma indireta como agentes de biocontrole. Essa biotecnologia microbiana é benéfica pois acelera o crescimento vegetal, incrementa a produtividade e a qualidade nutricional dos alimentos, além de aumentar a resistência das plantas contra estresses bióticos e abióticos. Portanto, considerando o potencial dos microrganismos como biopromotores de crescimento vegetal, conhecer sobre a interação desses com as plantas resultará em maior sucesso do uso da biotecnologia microbiana. Assim, essa revisão tem por objetivo abordar como os métodos de inoculação podem interferir no efeito benéfico do PGPM às plantas. Além de elucidar quais os mecanismos e benefícios do uso da biotecnologia microbiana ao vegetal.

Effects of Reducing Nitrogen Fertilizer and Improving Organic Fertilizer on Crop Yield, Soil Quality and Microbial Community in Five Years Wheat-Rice Rotation Field

Excessive application of nitrogen (N) fertilizer usually causes contamination of soil and groundwater. In this study, the rice yield and soil quality were investigated under different content of N fertilizer and amending organic compost (OC) or (and) crop residue (CR) in five-year wheat-rice rotated fields, and the soil microbial communities were inspected by means of Illumina sequencing. The results showed that rice yields were maintained at a high level although the N fertilizer was reduced to 80% of the normal content with amendment of OC and (or) CR. The PH was decreased and available phosphorus increased whenever the N fertilizer was normally applied or decreased when OC and (or) CR was amended, respectively. Available potassium was significantly increased when N fertilizer was reduced but OC and (or) CR was added. The abundance of bacterial and fungal communities was affected by OC or CR. Function prediction indicated that bacteria involved in DNA repair, carbohydrate digestion and absorption, amino acid degradation, caffeine metabolites were affected by OC or CR. Some plant growth promoting microbes (bacterial genus Pantoea, fungal gena Talaromyces and Scolecobasidium) were increased when OC or (and) CR was added. In addition, some nitrification or denitrification related bacteria (Candidatus nitrotoga, Nitrolancea, Noviherbaspirillum, Thioalkalispira) and fermentative metabolite bacteria (Lactobacillus) were increased when N fertilizer was reduced and OC or (and) CR was amended. These microbes may decompose the complex organic matter and improve nutrient transforming cycle to promote plant growth.

Potential Role and Utilization of Plant Growth Promoting Microbes in Plant Tissue Culture

Plant growth promoting microbes (PGPMs) play major roles in diverse ecosystems, including atmospheric nitrogen fixation, water uptake, solubilization, and transport of minerals from the soil to the plant. Different PGPMs are proposed as biofertilizers, biostimulants, and/or biocontrol agents to improve plant growth and productivity and thereby to contribute to agricultural sustainability and food security. However, little information exists regarding the use of PGPMs in micropropagation such as the in vitro plant tissue culture. This review presents an overview of the importance of PGPMs and their potential application in plant micropropagation. Our analysis, based on published articles, reveals that the process of in vitro classical tissue culture techniques, under strictly aseptic conditions, deserves to be reviewed to allow vitroplants to benefit from the positive effect of PGPMs. Furthermore, exploiting the potential benefits of PGPMs will lead to lessen the cost production of vitroplants during micropropagation process and will make the technique of plant tissue culture more efficient. The last part of the review will indicate where research is needed in the future.

Protists as main indicators and determinants of plant performance

Background Microbiomes play vital roles in plant health and performance, and the development of plant beneficial microbiomes can be steered by organic fertilizer inputs. Especially well-studied are fertilizer-induced changes on bacteria and fungi and how changes in these groups alter plant performance. However, impacts on protist communities, including their trophic interactions within the microbiome and consequences on plant performance remain largely unknown. Here, we tracked the entire microbiome, including bacteria, fungi, and protists, over six growing seasons of cucumber under different fertilization regimes (conventional, organic, and Trichoderma bio-organic fertilization) and linked microbial data to plant yield to identify plant growth-promoting microbes. Results Yields were higher in the (bio-)organic fertilization treatments. Soil abiotic conditions were altered by the fertilization regime, with the prominent effects coming from the (bio-)organic fertilization treatments. Those treatments also led to the pronounced shifts in protistan communities, especially microbivorous cercozoan protists. We found positive correlations of these protists with plant yield and the density of potentially plant-beneficial microorganisms. We further explored the mechanistic ramifications of these relationships via greenhouse experiments, showing that cercozoan protists can positively impact plant growth, potentially via interactions with plant-beneficial microorganisms including Trichoderma, the biological agent delivered by the bio-fertilizer. Conclusions We show that protists may play central roles in stimulating plant performance through microbiome interactions. Future agricultural practices might aim to specifically enhance plant beneficial protists or apply those protists as novel, sustainable biofertilizers.

Successful Plant Growth-Promoting Microbes: Inoculation Methods and Abiotic Factors

Plant-microbe interactions have been the subject of several biotechnological studies, seeking sustainable development and environmental conservation. The inoculation of plant growth-promoting microbes (PGPM) in agricultural crops is considered an environmental-friendly alternative to chemical fertilization. Microbial inoculants are mainly inoculated onto seeds, roots and soil. PGPM improve plant growth by enhancing the availability of nutrients, the regulation of phytohormones, and by increasing plant tolerance against biotic and abiotic stresses. One of the main obstacles with PGPM research are the inconsistent results, which may be the result of inoculation methods and abiotic factors, such as soil (nutrient or heavy metal contents and pH), water availability, light intensity and temperature. This review addresses how the PGPM inoculants act on plant growth, what mechanisms they use to survive under stressful environmental conditions, and how inoculation methods and abiotic factors can interfere on the success of microbial inoculation in plants, serving as a basis for research on plants-microorganisms interaction.