Elevated tropospheric ozone (O-3) may alter nitrous oxide (N2O) emissions from rice soils by affecting soil nitrogen pools and microbial activity. Understanding these interactions is essential for predicting the future behavior of rice ecosystems under elevated ozone stress. This study investigates the responses of N2O flux in relation to soil nitrogen (N) pools and microbial activity in rice soil subjected to four levels of elevated tropospheric O-3 (UC (ambient [O-3] in an open-field, 30 +/- 5 ppb), CC (ambient [O-3] within an open-top chamber (OTC), 30 +/- 5 ppb), EO40 (elevated [O-3] within an OTC, 40 +/- 5 ppb), and EO60 (elevated [O-3] within an OTC, 60 +/- 5 ppb). Rice soil exposed to e[O-3] exhibited significant reductions in microbial biomass nitrogen (29%), ammoniacal nitrogen (30%), and nitrate nitrogen (32%) concentration over ambient (CC). Rhizospheric denitrifier populations decreased by 11%, whereas seasonal N2O emission was decreased by 21% under e[O-3] as compared to CC. The PLS-PM model revealed that nitrifiers and denitrifiers exert a direct influence on N2O emissions, with a more pronounced effect under e[O-3] conditions compared to the CC. These insights enhance our understanding of the complex interactions between soil, plants, and microbial communities in an O-3-enriched environment.

The aus (Oryza sativa L.) varietal group comprises of aus, boro, ashina and rayada seasonal and/or field ecotypes, and exhibits unique stress tolerance traits, making it valuable for rice breeding. Despite its importance, the agro-morphological diversity and genetic control of yield traits in aus rice remain poorly understood. To address this knowledge gap, we investigated the genetic structure of 181 aus accessions using 399,115 SNP markers and evaluated them for 11 morpho-agronomic traits. Through genome-wide association studies (GWAS), we aimed to identify key loci controlling yield and plant architectural traits. Our population genetic analysis unveiled six subpopulations with strong geographical patterns. Subpopulation-specific differences were observed in most phenotypic traits. Principal component analysis (PCA) of agronomic traits showed that principal component 1 (PC1) was primarily associated with panicle traits, plant height, and heading date, while PC2 and PC3 were linked to primary grain yield traits. GWAS using PC1 identified OsSAC1 on Chromosome 7 as a significant gene influencing multiple agronomic traits. PC2-based GWAS highlighted the importance of OsGLT1 and OsPUP4/ Big Grain 3 in determining grain yield. Haplotype analysis of these genes in the 3,000 Rice Genome Panel revealed distinct genetic variations in aus rice. In summary, this study offers valuable insights into the genetic structure and phenotypic diversity of aus rice accessions. We have identified significant loci associated with essential agronomic traits, with GLT1, PUP4, and SAC1 genes emerging as key players in yield determination.

Rice grains are the major source of nutrition for more than half of the world's population. With increased frequencies of cyclones in the last decade during grain maturation stage of rice crop, most of the rice cultivars in lowland ecologies are getting affected by pre harvest sprouting due to flash flooding and incessant rains. Significant economic loss is incurred in the global food grain industry of cereals due to pre-harvest sprouting (PHS). It is very important to develop climate resilient varieties with PHS resistant traits introgressed in them. Well characterized PHS resistant rice genotypes with optimal dormancy that can serve as donors are need of the hour. We conducted an experiment to identify PHS resistant genotypes, and also determine to their physiological and biochemical characteristics. 96 diverse rice genotypes were evaluated for PHS resistance from 20 to 40 days after flowering (DAF). Based on their response, 16 contrasting genotypes were identified from 96 genotypes to further study the underlying mechanism of PHS resistance. The results revealed that, susceptible genotypes (8) exhibited very high germination percentage (4 to 87.5

In cereals, pre-harvest sprouting (PHS) or vivipary is a key physiological and agronomic trait that causes huge economic loss. PHS triggered by typhoons, cyclones, and high relative humidity at the late seed maturation stage is becoming a major threat to rice production in India. To explore the mechanism of PHS in rice, we evaluated 96 rice genotypes for PHS resistance and discovered 12 PHS resistant genotypes. These genotypes were classified into two groups susceptible and resistant, based on their phenotype. From the 96 genotypes, 16 contrasting genotypes were chosen, to unravel the underlying mechanism associated with PHS resistance. The results revealed that resistant genotypes had 0% germination at all the flowering stages (20 to 40 DAF), while susceptible genotypes had 4 to 87.5% germination from 20 to 40 DAF. In terms of pericarp color, 7 out of 8 resistant genotypes had red/pigmented pericarp color while the susceptible genotypes had white/non-pigmented pericarp color. The carotenoid content of leaves and seeds from 20 to 40 DAF was also measured and found to be significantly higher in resistant genotypes than susceptible genotypes. Carotenoids have been demonstrated to increase resistance by assisting in the synthesis of ABA and thereby seed dormancy. The 12 resistant genotypes were examined for germination to decide the duration of dormancy. The duration of dormancy varied in these 12 resistant genotypes varying from 10 days up to 40 days after harvest. These findings suggest that these novel PHS resistant genotypes (PB-68, HT-81, PB-50(1), HT-86, HT-20, Mahulata, PB-285, PB-47, NHN-279, PB-65, PB-259 and Budidhan) may be exploited as donors in the crop improvement programmes to generate PHS resistant genotypes.

The present study was conducted to evaluate the performance of seven rice genotypes using morphological, physiological and biochemical parameters, under induced drought (water stress) conditions at seedling level using PEG6000 in Hoagland's medium. At the end of the stress period sampling was done to record the root and shoot lengths and various physiological parameters viz., total chlorophyll content, cell membrane stability index (MSI), relative water content were estimated. Proline and Malondialdehyde (MDA) content were also estimated as biochemical parameters. The results obtained from the study revealed the existence of significant variation in the seven genotypes studied for different physiological and biochemical parameters. Out of the seven genotypes studied, HT-18 (AC-34973) had performed better than the tolerant check CR-143-2-2 and showed better root and shoot growth, maintained higher total chlorophyll content (2.6 mg/gm FW), relative water content (61.3%) and membrane stability index (MSI) (52.9%), it has also shown higher proline content (20.52 ?moles/gm FW) and lesser MDA content (0.068) under stress. To assess the membrane integrity under osmotic stress, roots from all the genotypes grown in hydroponic culture with 20% PEG were stained with Evan's blue, where the stress effect is directly reflected on the intensity of Evans blue uptake by the cell. Because of more membrane damage, the roots of the susceptible genotype, IR-64, had taken up more stain than the roots of tolerant genotype HT-18. The present study has identified HT-18 as seedling level drought tolerant genotype.

Rice is a crop of primary importance in regions, where two-thirds of the world’s starving population reside. Recent climate change projections anticipate spatial shift in precipitation pattern and increase of flooding events that may have negative effects on rice yield and economic returns. Efforts for increasing rice production in areas prone to submergence stress will directly benefit hundreds of millions of people dependent on rice as their staple food. This necessitates an objective review of physiological mechanisms and management practices, which could sustain crop productivity under partial or complete submergence. Submergence usually reduces photosynthesis rate that results in quick depletion of the carbohydrate reserve and ultimately the plant dies. Varieties introgressed with SUB1A QTL maintains higher activity of alcohol dehydrogenase and low rate of chlorophyll degradation and thus exhibits better survival under submergence. Prolonged submergence results in a significant reduction in soil redox potential and the heavy influx of flood water promotes runoff, volatilization and deep percolation which leads to loss of sizeable amount of nutrients and ultimately causes nutrient deficiency in soil. Thus, to ensure optimum yield, it is essential to alter the nutrient schedule when plant is subjected to submergence stress. Agronomic management practices like seed priming, higher seed rates, alteration in crop geometry and other improved seeding methods enhance production efficiency by boosting germination, early growth and optimum partitioning of photosynthates to vegetative and reproductive parts. This review critically explores the complex problems faced by rice crop during submergence, physiological mechanisms that helps plant to cope up the submergence stress, as well as available cost-effective management strategies to arrest the yield decline.

In the human diet, particularly for most of the vegetarian population, mungbean ( Vigna radiata L. Wilczek) is an inexpensive and environmentally friendly source of protein. Being a short-duration crop, mungbean fits well into different cropping systems dominated by staple food crops such as rice and wheat. Hence, knowing the growth and production pattern of this important legume under various soil moisture conditions gains paramount significance. Toward that end, 24 elite mungbean genotypes were grown with and without water stress for 25 days in a controlled environment. Top view and side view (two) images of all genotypes captured by a high-resolution camera installed in the high-throughput phenomics were analyzed to extract the pertinent parameters associated with plant features. We tested eight different multivariate models employing machine learning algorithms to predict fresh biomass from different features extracted from the images of diverse genotypes in the presence and absence of soil moisture stress. Based on the mean absolute error (MAE), root mean square error (RMSE), and R squared ( R 2 ) values, which are used to assess the precision of a model, the partial least square (PLS) method among the eight models was selected for the prediction of biomass. The predicted biomass was used to compute the plant growth rates and water-use indices, which were found to be highly promising surrogate traits as they could differentiate the response of genotypes to soil moisture stress more effectively. To the best of our knowledge, this is perhaps the first report stating the use of a phenomics method as a promising tool for assessing growth rates and also the productive use of water in mungbean crop.

Drought is a leading abiotic constraints for onion production globally. Breeding by using unique genetic resources for drought tolerance is a vital mitigation strategy. With a total of 100 onion genotypes were screened for drought tolerance using multivariate analysis. The experiment was conducted in a controlled rainout shelter for 2 years 2017–2018 and 2018–2019 in a randomized block design with three replications and two treatments (control and drought stress). The plant was exposed to drought stress during the bulb development stage (i.e., 50–75 days after transplanting). The genotypes were screened on the basis of the drought tolerance efficiency (DTE), percent bulb yield reduction, and results of multivariate analysis viz. hierarchical cluster analysis by Ward’s method, discriminate analysis and principal component analysis. The analysis of variance indicated significant differences among the tested genotypes and treatments for all the parameters studied, viz. phenotypic, physiological, biochemical, and yield attributes. Bulb yield was strongly positively correlated with membrane stability index (MSI), relative water content (RWC), total chlorophyll content, antioxidant enzyme activity, and leaf area under drought stress. The genotypes were categorized into five groups namely, highly tolerant, tolerant, intermediate, sensitive, and highly sensitive based on genetic distance. Under drought conditions, clusters II and IV contained highly tolerant and highly sensitive genotypes, respectively. Tolerant genotypes, viz. Acc. 1656, Acc. 1658, W-009, and W-085, had higher DTE (>90%), fewer yield losses (<20%), and performed superiorly for different traits under drought stress. Acc. 1627 and Acc. 1639 were found to be highly drought-sensitive genotypes, with more than 70% yield loss. In biplot, the tolerant genotypes (Acc. 1656, Acc. 1658, W-085, W-009, W-397, W-396, W-414, and W-448) were positively associated with bulb yield, DTE, RWC, MSI, leaf area, and antioxidant enzyme activity under drought stress. The study thus identified tolerant genotypes with favorable adaptive traits that may be useful in onion breeding program for drought tolerance.

Crop productivity is greatly affected by soil salinity; therefore, improvement in salinity tolerance of crops is a major goal in salt-tolerant breeding. The Salt Overly Sensitive (SOS) signal-transduction pathway plays a key role in ion homeostasis and salt tolerance in plants. In plants pumping of Na+ from the root cells is mediated by the plasma membrane Na+/H+ antiporter (SOS1) which plays important role in preventing the accumulation of toxic levels of Na+ in cytosol. In the present study, OsSOS1 (NHX7), gene was overexpressed in rice (var-Vikas) by Agrobacterium mediated In Planta transformation technique. To screen putative T1 plants for salt tolerance, stringent salt screening test was followed and root and shoot growth of transformants were used as selection criterion. Some of the putative transgenics showed significantly higher root growth compared to wild type. To confirm the presence of transgene in putative T1 transgenic plants, PCR based approach was followed using genomic DNA. The result showed that 16 % of the selected seedlings from the stringent salt screening test were PCR positives. Five selected lines were positive for RT-PCR analysis. Physiological studies such as chlorophyll content, membrane permeability, cell viability and sodium /potassium content analysis were also conducted to assess their levels of tolerance. Some of the T1 transformants showed lower percent reduction in chlorophyll content and less membrane leakage, higher cell viability and maintained higher K/Na ratio after NaCl treatment compared to wild type. These results clearly demonstrate that transgenic rice plants overexpressing OsSOS1 have better salt-tolerance. This could be attributed to extrusion of excess Na+ from cytosol into the apoplast and thereby reducing the toxic effects of Na+in the cell.

Declining soil fertility, imbalanced and non-judicious application of major fertilizers, decreasing crop productivity and produce quality and malnutrition among burgeoning human population are some of the major challenges of the present time. An experiment was conducted to assess role of N nutrition of wheat crop on efficiency for plant micronutrient uptake and their subsequent accumulation in the grain. The study involved measuring the effect of varying level fertilizer N application (N0, N120, N150 and N200 kg N ha-1) on root uptake, shoot partitioning and grain accumulation of iron (Fe) and zinc (Zn) in two bread wheat cultivars HD 2967 and DPW 621-50. N fertilizer application, in general, bettered plant vigor as evident from high root and shoot mass, root surface area and flag leaf area of N fertilized plants than those maintained without N. Fertilizer N application improved plant N status and shoot and grain concentration of Fe and Zn, more so in a dose dependant manner. Root to shoot and shoot to grain translocation efficiency for Fe and Zn increased with increasing availability of soil N. Higher biomass production with N fertilization led to a dilution effect on Fe and Zn concentration and caused a reduction in nutrient use efficiency for Fe, Zn and N with N than without N treatment. The concentration of these microelements in wheat shoot and grain increased with increasing N fertilizer application, reaching the highest at N150. Further, increase in N availability did not significantly improve the grain micronutrients. These results indicate that fertilizer N management of crops is critical determinant of Fe and Zn accumulation in the grain. Improved sink demand and efficient retranslocation of micronutrients at high N availability could be the underlying operative mechanisms responsible for agronomic biofortification.

Despite the rapid development of plant genomic technologies, a lack of advancement in high-throughput image based plant phenotyping capabilities limits our ability to dissect the genetics of quantitative traits. Effective, high-throughput image based phenotyping platforms have recently been developed to solve this problem. In high-throughput phenotyping platforms, a variety of imaging methodologies are being used to collect data for quantitative studies of complex traits related to the growth, yield and adaptation to biotic or abiotic stress (drought, disease, insects, and salinity). These imaging techniques include visible (RGB) imaging, spectroscopy imaging (multispectral and hyperspectral remote sensing), thermal infrared imaging, fluorescence imaging. This paper presents a brief review on these imaging techniques and their applications in plant phenotyping. The features used to apply these imaging techniques to plant phenotyping for abiotic stresses are described and discussed in this review.

Iron (Fe) and zinc (Zn) are important micronutrients required for various metabolic functions in plants and are considered a serious nutritional constraint in human beings. Global bio-fortification efforts are marred by low and imbalanced availability of these two minerals in the cultivable soil which negatively affects both the quality and quantity of cereal grain production. Present study was conducted to investigate the effect of variable Fe and Zn supply on Fe, Zn and N uptake in two bread wheat cultivars in nutrient solution culture. Zinc and Fe availability at 0.5 and 50 µM, respectively increased plant dry matter accumulation and leaf chlorophyll content, while an excess Zn supply (10 µM) at sufficient Fe (100 µM) significantly reduced shoot and root dry mass and total chlorophyll content of both the wheat cultivars when compared with the micronutrient deficient control. Iron and Zn availability positively impacted the plant N nutrition and that Fe and Zn have synergistic effect on the root release of phytosiderophore. Zinc and Fe were observed to facilitate root to shoot translocation of each other while competitive inhibition between Fe/Zn ratio was observed at the level of root uptake. It is, thus, suggested that crop management strategy should adopt a balanced fertilization approach giving equal importance to both macro- as well as micro-nutrient supplementation in order to achieve vigorous vegetative growth, grain yield and nutritional quality.

An efficient reproducible protocol has been established for raising salinity tolerant fingermillet through in vitro Agrobacterium mediated transformation. To enhance the salinity tolerance in fingermillet a double gene construct of PgNHX1 (from Pennisetum glaucum) and AVP1 (from Arabidopsis thaliana) was developed using the plant binary expression vector pCAMBIA 1301. This was then mobilized into electro competent Agrobacterium tumefaciens strain EHA105 and used for transforming fingermillet var. GPU28. GUS histochemical assay was monitored for confirmation of callus transformation. The putative transformants were acclimatized in incubation chamber for two weeks and then transplanted in greenhouse for further acclimatization. Putative transgenics were confirmed by physiological analysis and PCR amplification of genomic DNA using primers. The putative transgenic plants showed higher salt tolerance of 300mM compared to treated wild type plants. This is the first study in fingermillet reporting the expression of double gene construct of PgNHX1 and AVP1 for salinity tolerance.