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In the present study, we examined the synergistic effect of phosphate solubilizing bacteria (PSB) and the chemical phosphate on the growth, photosynthetic efficiency, phosphorus (P) uptake, antioxidant activity, and yield of upland rice. Three effective bacterial strains with potent P solubilizing activity viz., Bacillus licheniformis (688.18 µg ml−1), Pantoea dispersa (570.90 µg ml−1), and Staphylococcus sp. (551.81 µg ml−1), were isolated from rice rhizosphere to study their impact on upland rice growth and yield under field conditions for two consecutive years. The experiment data revealed significant increments in shoot height, shoot dry weight, total chlorophyll, carotenoid, chlorophyll fluorescence (fv/fm), P uptake, antioxidant activity, and yield characteristics in upland rice treated with individual PSB or their consortia alone, compared to uninoculated control. However, the integrated use of PSB with 50% recommended P dose showed maximum increment in growth indices (21.25%, 21.86% increase in shoot length and 87.18%, 97.06% increase in shoot dry weight), P uptake (110.37%, 122.78% increase), and yield (50.58%, 35.64% increase) compared to uninoculated control for 2018 and 2019, respectively, indicating a reduction in the dependence of chemical P fertilizer by 50%. Therefore, it can be concluded that combined application of PSB and 50% recommended dose of chemical P can be implied for the sustainable cultivation of upland rice systems to give maximum benefits to the farmers and the environment.

Phosphorus is the second most critical macronutrient after nitrogen required for metabolism, growth, and development of plants. Despite the abundance of phosphorus in both organic and inorganic forms in the soil, it is mostly unavailable for plant uptake due to its complexation with metal ions in the soil. The use of agrochemicals to satisfy the demand for phosphorus to improve crop yield has led to the deterioration of the ecosystem and soil health, as well as an imbalance in the soil microbiota. Consequently, there is a demand for an alternate cost-effective and eco-friendly strategy for the biofortification of phosphorus. One such strategy is the application of phosphate-solubilizing microorganisms which can solubilize insoluble phosphates in soil by different mechanisms like secretion of organic acids, enzyme production, and excretion of siderophores that can chelate the metal ions and form complexes, making phosphates available for plant uptake. These microbes not only solubilize phosphates but also promote plant growth and crop yield by producing plant-growth-promoting hormones like auxins, gibberellins, and cytokinins, antibiosis against pathogens, 1-aminocyclopropane-1-carboxylic acid deaminase which enhances plant growth under stress conditions, improving plant resistance to heavy metal toxicity, and so on. Pyrroloquinoline quinine (pqq) and glucose dehydrogenase (gcd) are the representative genes for phosphorus solubilization in microorganisms. The content presented in this review paper focuses on different mechanisms and modes of action of phosphate-solubilizing microorganisms, their contribution to phosphorus solubilization, growth-promoting attributes in plants, and the molecular aspects of phosphorus solubilization.

The onset of nineteenth century along with anthropogenic pressure paved the way for global climatic variation which is a major factor for global undernourishment, malnutrition and endangered food security. The major upshot of climate change is abiotic stress like salinity, flood and drought that declines the agricultural productivity. Abiotic stress hampers the survival of the plants and restricts their growth and development. Each abiotic stress confers negative impact on plants by altering its physiology, morphology and metabolism. Production of reactive oxygen species during stress condition alters the structure and metabolic function in plants and restricts its growth. Drought is one of the serious threats to crop productivity among the abiotic stress that imposes multidimensional effects on plants. Drought alters physiology and anatomy of the plants and is the main reason for economic loss in terms of livestock and grain yield in both developed and developing countries. Plants adapt several resistance mechanisms to cope up with the drastic impact of stress. Main tolerance mechanisms are alteration in membrane structure, escaping the unfavourable conditions, activation of antioxidant defense system, production of compatible solutes for maintaining osmotic balance of the cell. Present manuscript focuses on the outcome of major abiotic stress in plants and their tolerance strategies against the variable environmental conditions.

Effect of zinc and iron interaction on their distribution was examined in two wheat genotypes (UP262 and UP2628) under foliar application of 0, 0.25 and 0.50% ZnSO4 solution tagged with 925 KBq of Zn65 pot-1 for Zn and 0, 0.5 and 1.0% FeSO4 solution tagged with 925 KBq of Fe59 pot-1 for Fe at 30, 60 and 90 days after planting. Maximum grain yield of UP2628 (2.7 g pot-1 ) was recorded at 0.5%ZnSO4+0%FeSO4 while that of UP262 (2.63 g pot-1 ) was recorded at 0.5%ZnSO4+1.0%FeSO4. The highest straw yield of UP2628 (2.75 g pot-1 ) was noted at 0.5% ZnSO4+1.0%FeSO4 while that of UP262 (2.91 g pot-1 ) with 0.5%ZnSO4+0.5%FeSO4. Application of 0.5% and 1.0% FeSO4 reduced the accumulation of 65Zn in all parts of both the varieties. Regarding the 59Fe accumulation, it was found to be decreased with the increased application of ZnSO4 solution from 0.25% and 0.5% as compared to without application of Zn. On comparing translocation efficiencies of both the varieties, UP2628 showed better translocation thus accumulated higher zinc and iron. Therefore, variety UP2628 can be used further for crop improvement programme.

Soil is a powerful nonrenewable asset that embraces life on earth by furnishing nutrients to plant. Degradation of soil health due to indiscriminate use of chemical fertilizers and industrialization has become predominant environmental concern with high preeminence. In view of the present scenario, soil microbes are the most important candidates for improving soil fertility and health. The plant growth-promoting microbes are used for enhancing soil fertility under stressed and normal environment. Soil holds variety of microbial species such as fungi, bacteria, mosses and liverwort. The prevalence of microbes is an indicator of soil biological activities and regulates physical and chemical properties of soil. It enhances soil health and crop productivity by diverse mechanisms like biofortification of nutrients, bioremediation of soil, regulation of nutrient cycling, antibiosis, rhizosphere competence, secretion of enzymes, stimulation of systemic resistance in host plant, and production of metabolites, volatile compounds and antifungal toxins against pathogens. Interaction of plant and microorganisms results in plant growth promotion and disease control under fluctuating environment and enables sustainable agriculture without compromising ecosystem balance. Thus, the inclusive use of plant growth-promoting rhizobacteria promotes soil fertility that encourages sustainable agriculture production under extreme condition.

The eighteenth century simultaneously with the onset of industrial revolution and introduction of steam engines witnessed a meteoric upsurge in urbanization coupled with harmful anthropogenic activities which in turn subsequently steered climatic changes prompting calamitous floods, drought, global warming and altered CO2 concentration in air. Drought is one of the most imperative abiotic stresses wherein water availability recedes the optimum water requirement to an extent causing significant reduction in yield potential. The augmentation of harmful reactive oxygen species (ROS), such as hydrogen peroxide (H2O2) and the superoxide and hydroxyl radicals, leads to an alteration in various morphological, physiological, biochemical and molecular pathways consequently triggering the accumulation of numerous compatible osmolytes such as glycine-betaine, soluble sugars and proline and regulated expression of other genes. Drought, most importantly, influences the process of photosynthesis through the depletion of photosynthetic pigments, distortion of the structure and morphology of mesophyll cells altering the photosynthesis and gas-exchange processes as well as diminishing the reduction (electron transfer) efficiency of PSII. Silicon, in conditions of drought stress, has emerged to be a magical bullet compensating the yield loss to a great extent. Furthermore, it contributes to the amelioration of photosynthetic efficiency through the optimization of thylakoid membrane protein components. It is perceived to enhance seed germination in lentil and form a Si-cuticle double-layer diminishing transpiration rate and water flow rate in xylem vessels improving WUE up to 35% in case of maize under water stress. Silicon thus can be ascertained as a promising component to exterminate the hostile consequences of drought stress.

Global warming is rising as a serious concern affecting agricultural production worldwide. Rice is a staple food crop and the threshold temperature for its pollination is 35 °C. A rise in temperature above this value can cause pollen sterility and may severely affect fertilization. Therefore, a study emphasizing the rise in temperature with respect to pollen viability was conducted with eleven rice genotypes during kharif seasons of 2010 and 2011 in indigenous field conditions. Increasing mean temperature by 12 °C at full flowering was found to severely affect the spikelet attributes of the crop. All genotypes showed spikelet sterility above 90% during both seasons. The study indicated that increased temperature may limit rice yield by affecting spikelet fertility and grain filling. The net reduction in grain yield was 30.4% and 27.6% in 2010 and 2011, respectively. A clear reduction in pollen size under high temperature was shown by scanning electron microscopy.

A field study was carried out to investigate the effect of induced high temperature stress on the activity of superoxide dismutase (SOD), catalase (CAT), peroxidase (POX), and proline content, membrane stability index and lipid peroxidation in terms of malondialdehyde content in six rice genotypes, viz., IET 21404, IET 21577, IET 21411, IET 21405, IET 21415 and KRH 2. Flag leaves of rice at flowering stage were used for the analysis of enzyme activities. Elevated temperature significantly increased the activity of SOD (46.05 %), POX (66.00 %), and CAT (41.83 %). This increase was associated with increase in lipid peroxidation and decrease in membrane stability. In general IET 21404 and IET 21577 showed relatively higher SOD, CAT and POX activity as compared to IET 21411, IET 21405, IET 21415 and KRH 2. Significant increase in proline content, malondialdehyde content and decrease in membrane stability index were observed in all the genotypes of rice at anthesis.

Zinc (Zn) is an important micronutrient for the physiology of plants. It is poorly available to the plants in soil solution. A pot experiment was conducted to evaluate effectiveness of various Zn application methods on key enzyme activities and protein content of two contrasting rice genotypes viz., PD16 (Zn efficient) and NDR359 (Zn inefficient). The treatments were, control (0 mg Zn kg(-1) soil), soil application (5 mg Zn kg(-1) soil), foliar application (0.5 % ZnSO4 + 0.25 % lime at 30, 60 and 90 days after transplanting), soil (5 mg Zn kg(-1) soil) + foliar application of 0.5 % ZnSO4 + 0.25 % lime at 30, 60 and 90 days after transplanting. Among all the methods tested soil+foliar application of Zn fertilizers was found most effective in increasing superoxide dismutase (SOD) and carbonic anhydrase (CA) activities as well as chlorophyll and protein content in both the rice varieties. NDR359, showed higher enzyme activities and more chlorophyll content in leaves than PD16, when Zn was applied either through foliar spray alone or in soil along with foliar application. Regarding the protein content in grains, PD16 showed higher protein content than NDR359, thus showed better translocation of Zn from leaves to grains.

Around half of the cereal growing soil in the world are zinc (Zn)-deficient and it severally affects the health of plants, animals and humans. In order to investigate the enrichment of Zn in cereals a pot experiment was conducted in two contrasting wheat genotypes viz., UP2628 (Zn efficient) and UP262 (Zn inefficient) under different meth ods of Zn application such as control (0 Zn), soil application (5 mg Zn/kg soil tagged with 3.7 MBq of 65 Zn/pot), foliar spray of 0.5% ZnSO 4 at 30, 60 and 90 days (tagged with 925 KBq of 65 Zn/pot), soil application (5 mg Zn/kg soil tagged with 3.7 MBq of 65 Zn/pot) + foliar spray of 0.5% ZnSO 4 at 30, 60 and 90 days (tagged with 925 KBq of 65 Zn/pot). Cultivars showed marked difference in 65 Zn accumulation and grain Zn content. In both contrasting genotypes the highest Zn content in grains was recorded under soil application + foliar spray of Zn fertilizers. Both UP262 and UP2628 showed similar accumulation of 65 Zn in leaves however, UP2628 exhibited better translocation efficiency and accumulated higher 65 Zn in stem and grains than UP262.

Nitrogen use efficiency, more specifically physiological nitrogen use efficiency depends primarily on management of N, one of the major essential nutrients. It is required in increased agricultural production and may possibly cause soil toxicity if fed in excess. Rate of N fertilizer application in fertile agricultural field and improved productivity in sterile soils require the improvement of NUE. A field experiment was therefore conducted to evaluate the effect of different N levels (N0, N50, N100 and N200) on rice genotypes. Vegetative plant growth was found to be reduced under N0 while improved at N200 level. Among the genotypes, highest PNUE (34.94) and correspondingly higher yield (7.15 ton ha−1) was observed for Krishna Hamsa. The other traits viz. plant height, no. of productive tillers and LAI exhibited higher values for Krishna Hamsa as well. Hence these can be utilized as physiological markers for the selection of rice genotypes efficient in N use.

Rice, one of the most important staple food crops of the world, suffers a major setback nutritionally, because it is deficient in bioavailable zinc. In an attempt to answer this problem a field study was performed for two years during 2010 and 2011. Rice plants were treated with selected plant growth promoting rhizobacteria (PGPR; P. putida, P. fluorescens, A. lipoferum, B 15, B 17, B 19, BN 17, and BN 30) and plant growth, zinc (Zn) content in different plant parts and grains was analyzed. The data obtained showed enhancement in rice growth and hence, increased rice yield in response to PGPR application. All isolates resulted in almost 1.5- to 2-fold increase in Zn content in roots, shoots as well as grains in comparison to the control. The bacterial isolates B 17, B 19, and BN 17 were of particular interest as they induced the movement of Zn from roots to shoots as well as from husk to the grains, thus making grains enriched in Zn (around 25% higher Zn content). Therefore, it can be concluded that appli...

A two-year field experiment was conducted to study the effect of three zinc levels 0, 20 kg ZnSO4 ha−1 and 20 kg ZnSO4 ha−1 + foliar spray of 0.5% ZnSO4 solution on plant height, leaf area, shoot biomass, photosynthetic rate and chlorophyll content in different wheat genotypes. Increasing zinc levels was found to be beneficial in improving growth and physiological aspects of genotypes. Soil application + foliar spray proved to be the best application in improving all the parameters. Zinc application brought about a maximum increment limit of 41.8% in plant height, 101.8% in leaf area, 86% in shoot biomass and 51.1% in photosynthetic rate irrespective of stages and year of study. A variation was found to occur among genotypes in showing responses towards zinc application and PBW 550 was found to be more responsive.

One of the major problems faced by the world today is micronutrient malnutrition, particularly in developing countries. Because majority of the population residing in these countries cannot afford supplements, biofortification of staple crops with essential micronutrients can be a viable solution. Therefore, the present investigation was carried out to evaluate the potential of plant growth-promoting rhizobacteria (PGPR) for increasing the deposition of zinc and iron in the edible portion of rice (Oryza sativa L.) grains, i.e., endosperm. Application of PGPR increased iron and zinc content in the plants, as demonstrated by the increase in catalase and carbonic anhydrase activity. Different bacterial isolates showed differential zinc and iron uptake potential. All the bacterial isolates caused an increase in the grain zinc and iron content, whereas only some of the isolates, viz., B 15, BN 17, B 17, and B 19, primarily showed endosperm deposits of zinc and iron. Hence, we concluded that PGPR can help in in...

Zinc is essentially required for crop growth and its insufficient supply to the plants may severely limit the yield traits of a crop. A field experiment was performed during rabi season of 2009–10 and 2010–11 to evaluate the performance of different wheat genotypes under different levels of zinc namely 0 kg ZnSO4 ha−1, 20 kg ZnSO4 ha−1 and 20 kg ZnSO4 ha−1 along with foliar spray of 0.5% solution of ZnSO4. Genotypes responded positively in terms of tiller number, grain and biological yield, spikelet length, spikelet number, grain number and thousandgrain weight. The best response was observed with the application of 20 kg ZnSO4 ha−1 along with foliar spray of 0.5% solution of ZnSO4. Zinc application brought about a maximum increase of 58.6% in tiller number, 63.7% in thousand-grain weight, 40.5% in biological yield, 66.1% in grain yield irrespective of genotypes and the year of study. Wheat genotypes exhibited a variation in their performance which has been exploited in this study. Genotypes UP-262, PBW-175, PBW-343 were found to be superior for one or the other yield contributing factors.

A field study was carried out to investigate the effect of three Zn levels 0, 20 kg ZnSO4 ha(-1) and 20 kg ZnSO4 ha(-1)+ foliar spray of 0.5 % ZnSO4 on superoxide dismutase activity, acid phosphatase activity and grain yield and a pot experiment to study the effect of zinc deficient and sufficient conditions on organic acid exudation. Increasing Zn levels was established as beneficial in improving the enzyme activities of genotypes. Combined foliar and soil application of Zn proved to be superior of all the treatments. Zinc application resulted in a maximum increment limit of 96.8 % in superoxide dismutase activity, 75.76 % in acid phosphatase activity, and a decrement limit of 88.57 % in oxalic acid exudation irrespective of stages and year of study. The increased enzyme activities had a positive impact on grain yield. As an average of all genotypes an improvement of 19.88 % in 2009 and 21.29 % in 2010 due to soil application while of 16.45 % in 2009 and 13.01 % in 2010 due to combined application was calculated for grain yield. There existed a variation among genotypes in showing responses towards zinc application and the genotypes UP 2584 and PBW 550 were found to be more responsive.

A field study was conducted to ascertain the effect of three zinc (Zn) levels: 0, 20 kg ZnSO 4 /ha and 20 kg ZnSO 4 /ha + foliar spray of 0.5% ZnSO 4 , on wheat grain Zn content and factors contributing to or hindering in its bioavailability. Increasing Zn levels were established as serviceable in improving the nutritional status of genotypes. Soil application + foliar spray proved to be paramount for all the traits leading to an 80% increase in grain Zn content, 61.3% in methionine content and a decrease of 23.2% in phytic acid as an average of all genotypes and both years. The genotype UP 2382 was found more suited to Zn fertilization in allocating Zn and maintaining a lower phytate to Zn molar ratio.

Rice is inherently low in micronutrients, especially iron, which leads to severe malnutrition problems in rice-consuming populations. Different plant growth promoting rhizobacterial strains (PGPRs) (viz. Pseudomonas putida, Pseudomonas fluorescens , and Azospirillum lipoferum from a microbial collection and B 15, B 17, B 19, BN 17 and BN 30 isolated from the rhizospheric soils) were applied to field grown rice plants with an aim to increase the iron content of grains. 16S rRNA gene sequence showed that isolates belong to Enterobacteria species. Different param eters related to the increase in iron content of plants show an enhancement upon treatment of rice plants with PGPRs. Treatments with P. putida, B 17 and B 19 almost doubled the grain iron content. Besides this, the translocation efficiency of the iron from roots to shoots to grains was also enhanced upon treatment with PGPRs. It is therefore concluded that application of PGPR strains is an important strategy to combat the problem of iron deficiency in rice and consecutively in human masses.

K is the third most important plant macronutrient after nitrogen and phosphorus. It is absorbed from soil primarily in the form of K+ and is required in the plants for early growth, production, and modification of proteins, maintenance of water use efficiency, stand persistence, longevity, etc. The total K content in soil exceeds 20,000 ppm which is primarily divided into unavailable, slowly available, and readily available fractions of which readily available fractions constitute only 1–2 % of the total K available in the soil. To mobilize and utilize these large reserves, a viable strategy is the identification and utilization of K-solubilizing microorganisms (KSMs). Soil microbes playing a key role in K cycling have been known since a long time now; therefore, identification of KSMs and their utilization are of prime importance to reduce the fertilizer usage and the effects caused by effective fertilizer usage. Although many bacteria like Acidithiobacillus, Burkholderia, and Pseudomonas have been identified as the potential K solubilizers, a clear cut mechanism has not been reported. However, most solubilization activities of bacteria and fungi have been attributed to the activities like acid hydrolysis of K from minerals present in the soil, chelation by production of some organic acids, etc. Therefore, the content presented in this manuscript explores the applicability of these KSMs, their mode of action, and their percent contribution in K solubilization and availability to the plants.

In the area of agricultural practices, yield prediction relies on human expertise but it is not always reliable due to many reasons. Fuzzy logic system is a mathematical method of rule-based decision making and can be used to predict the yield of crops very effectively. It plays an essential role in the remarkable human ability to make rational decisions in an environment of uncertainty which affects the yield of seasonal crops. In the present study, Mamdani fuzzy rule based system is developed for prediction of economic yield of six different rice genotypes, KRH-2, PA-6129, PHB-71, AK-DHAN, NDR-359, VARADHAN. The proposed Mamdani rule based model uses different values of total dry matter and number of effective tillers of all the genotypes as input variables. No remarkable difference was found in the prediction of economic yield of all the rice genotypes obtained by fuzzy rule based model and yield obtained by field grown crop. Out of six genotype fuzzy system also predicted that KRH-2 is best in terms of economic yield when grown in normal sowing conditions.

In six cultivars of rice (Oryza sativa L.), Pusa Basmati 1, Basmati 370, Type III, Pant Dhan 4, CSR 10 and Pokkali, embryogenic callus growth, plant regeneration, and proline and total protein contents were studied under salt stress (on agar solidified media containing 0, 0.5, 1.0, 1.5 and 2.0 % NaCl). Four weeks after inoculation the callus fresh mass decreased with increasing salt concentration in all the six cultivars. The regeneration frequency in salt stressed callus was also lower as compared to control. 15 d and 30 d after inoculation proline content increased several fold whereas total protein content decreased markedly with increase in salt concentration.

Availability of Zn to plant is hampered by its immobile nature and adverse soil conditions. Thus, Zn deficiency is observed even though high amount is available in soil. Root-shoot barrier, a major controller of zinc transport in plant is highly affected by changes in the anatomical structure of conducting tissue and adverse soil conditions like pH, clay content, calcium carbonate content, etc. Zn deficiency results in severe yield losses and in acute cases plant death. Zn deficiency in edible plant parts results in micronutrient malnutrition leading to stunted growth and improper sexual development in humans. To overcome this problem several strategies have been used to enrich Zn availability in edible plant parts, including nutrient management, biotechnological tools, and classical and molecular breeding approaches.

BACKGROUND: In finger millet, calcium is one of the important and abundant mineral elements. The molecular mechanisms involved in calcium accumulation in plants remains poorly understood. Transcriptome sequencing of genetically diverse genotypes of finger millet differing in grain calcium content will help in understanding the trait. PRINCIPAL FINDING: In this study, the transcriptome sequencing of spike tissues of two genotypes of finger millet differing in their grain calcium content, were performed for the first time. Out of 109,218 contigs, 78 contigs in case of GP-1 (Low Ca genotype) and out of 120,130 contigs 76 contigs in case of GP-45 (High Ca genotype), were identified as calcium sensor genes. Through in silico analysis all 82 unique calcium sensor genes were classified into eight calcium sensor gene family viz., CaM & CaMLs, CBLs, CIPKs, CRKs, PEPRKs, CDPKs, CaMKs and CCaMK. Out of 82 genes, 12 were found diverse from the rice orthologs. The differential expression analysis on the basis of FPKM value resulted in 24 genes highly expressed in GP-45 and 11 genes highly expressed in GP-1. Ten of the 35 differentially expressed genes could be assigned to three documented pathways involved mainly in stress responses. Furthermore, validation of selected calcium sensor responder genes was also performed by qPCR, in developing spikes of both genotypes grown on different concentration of exogenous calcium. CONCLUSION: Through de novo transcriptome data assembly and analysis, we reported the comprehensive identification and functional characterization of calcium sensor gene family. The calcium sensor gene family identified and characterized in this study will facilitate in understanding the molecular basis of calcium accumulation and development of calcium biofortified crops. Moreover, this study also supported that identification and characterization of gene family through Illumina paired-end sequencing is a potential tool for generating the genomic information of gene family in non-model species.