Occurrence of Sphingomonas olei with elemental S oxidation capability in sodic soil: Potential role in sodicity reclamation and plant growth promotion.

The success of the sodic soil reclamation using elemental S (S°) depends on the population of the native S° oxidizers. Augmenting the native flora of the sodic soils with effective S° oxidizers can enhance the success of the sodic soil reclamation. Present study reports for the first time the S° oxidation potential of the Sphingomonas olei strain 20UP7 isolated from sodic soils with pHs 9.8 and ECe 3.6 dS m-1. Inoculation with S. olei strain 20UP7 caused 13.0-24.2 % increase in S° oxidation in different sodic soils (pHs 9.1-10.5). It improved the concentration of the Ca2+, Mg2+, PO43- and declined the HCO3- and total alkalinity of the soil solution. This isolate also showed appreciable P and Zn solubilization, indole acetic acid, ammonia, and titratable acidity production in the growth media. It tended to the formation of biofilm around sulphur particles. The PCR amplification with gene-specific primers showed the occurrence of soxA, soxB, and soxY genes with a single band corresponding to length of 850, 460, and 360 base pairs, respectively. The integration of the S. olei strain 20UP7 with S° caused 21.7-25.4 % increase in the rice and wheat yield compared to the soil treated with S° alone. This study concludes that the S. olei, native to high saline-sodic soils can be utilized for improving the sodicity reclamation and plant growth promotion using elemental S based formulations.

Conservation agriculture works as a catalyst for sustainable sodic soil reclamation and enhances crop productivity and input use efficiency: A scientific inquiry.

Soil sodicity is a growing concern for crop growth and development in arid and semi-arid regions of the world. Conservation agriculture (CA) provides an effective solution towards reclamation of degraded sodic lands and enhance the crop productivity. A field experiment was carried out to assess the sodic soil reclamation potential of CA based management practices including zero tillage, legume (mungbean; Mb) rotation, residue (+R) mulch, and subsurface drip irrigation (SDI) for three years under rice-wheat (RW) system. The system scenarios (Sc) comprised of multiple indicators to measure their impact on soil properties as well as system productivity, profitability, water and nitrogen use efficiency. The results indicated that soil pHs under Sc5-Sc8 (CA-based SDI scenarios) was significantly (p < 0.05) lowered by 2.16, 2.16 and 1.33% compare with mean of Sc1 and Sc2 (CT-based system; 9.10, 8.29 and 8.14) at all three soil layers (0-5, 5-15 and 15-30 cm), respectively. Similarly, the exchangeable sodium percentage (ESP) was lowered by 2.9, 11.2 and 14.9% under CA-based scenarios with residue management compared with CT-based system (mean of Sc1 and Sc2; 15.2, 17.2 and 28.6%) during the study. The concentration of extractable anions (COЗ2‾, HCOЗ‾, Cl‾) decreased notably whereas, soil organic carbon and soil solution cations (Na+, Ca2+, Mg2+) concentration were increased under CA based management SDI plots. In addition, CA with SDI scenarios (mean of Sc5-Sc8) proved to be more productive and water-efficient than CA-based flood irrigation (FI; mean of Sc3 and Sc4). Moreover, CA-based FI and SDI scenarios saved 29.5 and 60.7% irrigation water, and improved the partial factor productivity of nitrogen (PFPN) by 6.8 and 24.4%, respectively compared to CT-R (conventional tillage without residue) based Sc1. Therefore, CA practices can potentially reduce sodicity and improve soil chemical properties for profitable crop cultivation.

Screening of quinoa (Chenopodium quinoa Willd.) germplasms under high-SAR saline water on the basis of growth, yield, and multivariate analysis.

Increasing soil and underground water salinization with decreasing availability of fresh water has become a potential threat to sustainable crop production in arid and semi-arid areas globally. Introduction and evaluation of salt-tolerant halophytic crops is one of the sustainable ways to preserve productivity in saline ecosystems. This study was aimed to screen quinoa germplasms under high-sodium adsorption ratio (SAR) saline stress. Thirteen quinoa germplasms were evaluated under four levels [best available water (BAW), 8, 16, and 24 dSm-1] of high-SAR saline water irrigation. The evaluation was carried out based on growth, yield, and ionic content parameters along with statistical tools such as multivariate analysis, salt tolerance indices, and correlation. The results showed that the salinity levels of 16 and 24 dSm-1 resulted in increase of chlorophyll content relative to BAWand 8 dSm-1. The germplasm CSQ2 recorded the highest proline content (163.7 mg g-1 FW) at 24 dSm-1. Increasing levels of salinity reduced relative water content in plant leaves, and the germplasm CSQ2 showed minimal reduction of 4% at 24 dSm-1. Na+ and K+ contents in the plants increased with increasing salinity levels, while the K+/Na+ ratio decreased. The grain yield of quinoa germplasms ranged between 3.5 and 14.1 g plant-1. The germplasm EC507740 recorded the highest grain yield (7.0 g plant-1) followed by CSQ1 and CSQ2 at a maximum stress of 24 dSm-1. Principal component analysis (PCA) and correlation elucidated that Na+ content in plants was negatively correlated with all the studied traits except SPAD, proline content, and K+ content. The different salt tolerance indices indicated that the germplasms EC507740, CSQ1, CSQ2, EC507738, and IC411825 were more stable at high-SAR salinity, while PCA showed the germplasms EC507740 and CSQ2 as the most salt-tolerant germplasms.

Characterization of flue gas desulphurized (FGD) gypsum of a coal-fired plant and its relevant risk of associated potential toxic elements in sodic soil reclamation.

Thermal Power Plant generates FGD gypsum as by-product during coal combustion. This study evaluates the characterization (spectroscopic and elemental), potentially toxic elements (PTEs) distribution, and environmental risk assessment of FGD gypsum for safe and sustainable use in agriculture. The XRD and SEM analysis confirmed the dominance of crystalline CaSO4·2H2O in FGD gypsum. The order of concentrations of PTEs in FGD gypsum was Fe > Al > Mn > Zn > Ni > Co. The residual fraction was the dominant pool, sharing 80-90% of the total PTEs. The heavy metals (HMs) were below the toxic range in the leachates. The Co, Ni, Al, Fe Mn, Zn had low (< 10%) risk assessment code and the ecotoxicity was in the range of 0.0-7.46%. The contamination factor was also low (0.0-0.16) at the normal recommended doses of FGD gypsum application for sodicity reclamation. The enrichment factor was in the order of Al < Mn < Co < Zn < Ni. Mn [enrichment factor (Ef) 1.2-2.0] and Co (Ef 1.7-2.8) showed negligible enrichment of metals, whereas Ni (Ef 4.3-5.2) and Zn (Ef 4.5-5.6) reported moderate accumulation in soil. The application of FGD gypsum @ 10 t ha-1 for sodicity reclamation will develop a geo-accumulation index below the critical values indicating its safe and sustainable use to achieve land degradation neutrality (LDN) and UN's Sustainable Development Goals.

Restoring soil quality and carbon sequestration potential of waterlogged saline land using subsurface drainage technology to achieve land degradation neutrality in India.

Subsurface drainage (SSD) has been proved to be an effective technology to reclaim waterlogged saline soils. Three SSD projects were implemented in Haryana, India in 2009, 2012 and 2016 to study the long term effect of SSD (10, 7 and 3 years) operation on restoring productivity and carbon sequestration potential of degraded waterlogged saline soils under prevalent rice-wheat cropping system. These studies indicated that successful operation of SSD improved soil quality parameters such as bulk density, BD (from 1.58 to 1.52 Mg m-3), saturated hydraulic conductivity, SHC (from 3.19 to 5.07 cm day-1); electrical conductivity, ECe (from 9.72 to 2.18 dS m-1), soil organic carbon, OC (from 0.22 to 0.34 %), dehydrogenase activity, DHA (from 15.44 to 31.65 µg g-1 24 h-1), and alkaline phosphatase, ALPA (from 16.66 to 40.11 µg P-NP g-1 h-1) in upper soil surface (0-30 cm). The improved soil quality resulted in increased rice-wheat system yield (rice equivalent yield) by 328 %, 465 % and 665 % at Kahni, Siwana Mal and Jagsi sites, respectively. Studies also revealed that carbon sequestration potential of degraded land increased with the implementation of SSD projects. The principal component analysis (PCA) showed that % OC, ECe, ALPA, available N and K content were the most contributing factor for soil quality index (SQI). The overall result of the studies showed that SSD technology holds great potential to improve soil quality, increase crop productivity, farmers' income and ensure land degradation neutrality and food security in waterlogged saline areas of western Indo Gangetic Plain of India. Hence, it can be concluded that large scale adoption of SSD may fulfill the promise "No poverty, Zero hunger, and Life on land" sustainable development goals of United Nation in degraded waterlogged saline areas.

Sodicity stress differently influences physiological traits and anti-oxidant enzymes in pear and peach cultivars.

Background: The growth and physiological responses to sodicity stress of pear and peach are poorly understood. Insights into how sodicity stress alters tree physiology remain vital to developing salt tolerant scion and rootstock cultivars. Methods: The effects of sodicity stress (soil pHs ~8.8) on tree growth and physiological traits of field grown trees of pear cultivars Punjab Beauty and Patharnakh, and peach cultivars Partap and Shan-e-Punjab were recorded using standard procedures. Sodicity-induced changes in oxidative stressors, proline, anti-oxidant enzymes and leaf ions were measured to draw inferences. Results: Sodicity-induced reductions in vegetative growth were particularly marked in Patharnakh pear and Partap peach compared with other cultivars. Although sodicity stress triggered a significant increase in leaf malondialdehyde (MDA) and hydrogen peroxide (H2O2), their levels relative to controls were much higher in peach than in pear; reflecting that peach suffered from greater oxidative stress. Interestingly, MDA and H2O2 levels did not seem to be deleterious enough to trigger proline-induced osmotic adjustment in pears. The activities of anti-oxidant enzymes strongly varied with the cultivar; specifically, the sodicity-induced increases in CAT and SOD activities were much higher in Punjab Beauty pear and Shan-e-Punjab peach. Principal Component Analysis revealed an explicit convergence between CAT and SOD activities in Punjab Beauty and Shan-e-Punjab cultivars in response to sodicity-induced oxidative stress. Correlation analysis revealed that leaf Na+ strongly inhibited tree growth in peach than in pear. Leaf K+ and proline were found to be the major osmolytes in sodicity-stressed pear and peach cultivars, respectively. Conclusions: We have for the first time studied the effects of sodicity stress on important tree growth and physiological traits of commercially important pear and peach cultivars. Our findings revealed a marked suppressive effect of sodicity stress on tree growth in peach than in pear. The sodicity-induced upticks in leaf malondialdehyde, hydrogen peroxide and Na+ seemed to induce proline-mediated osmotic adjustment in peach but not in pear. The overall better sodicity tolerance in pear compared to peach was ascribed to increased activities of anti-oxidant enzymes catalase and superoxide dismutase enzymes together with restricted Na+ uptake and better leaf K+ levels. Further investigations are needed to elucidate the effects of sodicity stress on genetic and transcriptional changes, and on fruit yield and quality.

Conservation Tillage and Waste Crop Residue Based Zinc Fortification in Rice and Wheat under Reclaimed Sodic Soils: Progress toward Nutrient Circularity and Sustainability.

Nearly 50% of the population across the globe is at risk of malnutrition with respect to zinc (Zn) in areas where a cereal based dietary system dominates. The present study estimated daily Zn intake in humans through field experiments in reclaimed sodic soil, utilizing waste crop residue (CR) in conservation tillage where CR played a vital role in enhancing Zn uptake in rice and wheat grains. Zn dynamics, its bioavailability, interaction with soil properties, and plausible contribution in dietary intake were studied extensively to supplement the research. A higher mobility factor (2.70%) and plant available Zn resulted in its higher uptake in rice (58.2 mg kg-1) and wheat (67.2 mg kg-1) under zero tillage in rice followed by zero tillage in wheat where CR was retained on the surface (ZTR-ZTW+CR). Daily Zn intake was found to be maximum (0.651 mg kg-1 day-1) under ZTR-ZTW+CR, demonstrating zinc sufficiency. Thus, this study may help in formulating actionable policies for combating both nutritional security and environmental hazards due to CR burning.

Characterization and ecotoxicological risk assessment of sewage sludge from industrial and non-industrial cities.

The present study highlights the occurrence and the temporal variations of physicochemical properties, and heavy metals in the sludge from sewage treatment plants (STPs) located in industrial (two sites) and non-industrial (one site) cities of Haryana, India. The sludge was acidic (5.59) to neutral (7.21) with a mean EC of 7.4 dS m-1. Prominent heavy metals present in the sewage sludge from industrial sites were Cd, Ni, and Cr with maximum values of 2.83, 1449.0, and 3918.5 mg kg-1, respectively. The contamination and enrichment factor better explained the buildup of Ni, Cr, and Cu in the sewage sludge from industrial sites. The pH, total carbon, phosphorus, and other water-soluble anions, viz. SO42-, Cl-, HCO3-, and PO43-, were the most important attributes of sludge controlling the binding and removal of the metals with particulate matters during the phase separation in STPs. These attributes explained about 90% of the variation in Cd, Ni, Cr, Cu, Mn, and Zn content of the sludge from different STPs. Sludge from the non-industrial site had a low potential ecological risk index of 74.0 compared to a very high-risk index of 2186.5 associated with the industrial sites. This study concludes that besides the concentration of the heavy metals, the enrichment factor coupled with geo-accumulation or ecological risk index can effectively categorize the sludge. However, these indices need to be linked with bioaccumulation, bioaccessibility, and biomass quality under different agroecologies for guiding the safer use of sewage sludge in agriculture.

Irrigation water quality, gypsum, and city waste compost addition affect P dynamics in saline-sodic soils.

The amendments used for sodicity reclamation also profoundly influence P dynamics and leaching losses. This study characterized the effect of irrigation water quality on P dynamics and leaching from saline-sodic soil during reclamation utilizing gypsum alone or in combination with manure and city compost. Changes in properties of unleached and leached soils were fitted with labile P pools using redundancy analysis. The relation between leachate properties and P loss was explained by means of monitoring leachate properties up to ten pore volumes. During incubation, the water-extractable P (PH2O) concentration was greater than Olsen's P (PNaHCO3) in all treatments. The PNaHCO3 decreased in proportion to the amount of gypsum applied. Applying the organics with gypsum increased the PNaHCO3, PH2O, and organic P concentration compared to gypsum alone. The labile P pools in soil were positively correlated with HCO3- content (r = 0.39-0.77; P < 0.05) of leached and unleached soils. Adding gypsum and compost caused a 10-14% decrease in cumulative P leaching. The cumulative P leaching were greater with rainwater compared to saline water of SAR (sodium adsorption ratio) 5 and 15. The CO32-, HCO3-, pH, and SO42-content of the leachate explained about 71% variability in total P leaching (adj. R2 = 0.71; P < 0.001). This study concludes that low electrolyte water had a greater risk of P leaching and associated environmental pollution. Leaching of the saline-sodic soil amended with gypsum and city waste compost with low SAR saline water can reduce P leaching compared to good quality rainwater.

Linking genome wide RNA sequencing with physio-biochemical and cytological responses to catalogue key genes and metabolic pathways for alkalinity stress tolerance in lentil (Lens culinaris Medikus).

BACKGROUND: Alkaline soils cause low productivity in crop plants including lentil. Alkalinity adaptation strategies in lentil were revealed when morpho-anatomical and physio-biochemical observations were correlated with transcriptomics analysis in tolerant (PDL-1) and sensitive (L-4076) cultivars at seedling stage. RESULTS: PDL-1 had lesser salt injury and performed better as compared to L-4076. Latter showed severe wilting symptoms and higher accumulation of Na+ and lower K+ in roots and shoots. PDL-1 performed better under high alkalinity stress which can be attributed to its higher mitotic index, more accumulation of K+ in roots and shoots and less aberrantly dividing cells. Also, antioxidant enzyme activities, osmolytes' accumulation, relative water content, membrane stability index and abscisic acid were higher in this cultivar. Differentially expressed genes (DEGs) related to these parameters were upregulated in tolerant genotypes compared to the sensitive one. Significantly up-regulated DEGs were found to be involved in abscisic acid (ABA) signalling and secondary metabolites synthesis. ABA responsive genes viz. dehydrin 1, 9-cis-epoxycarotenoid dioxygenase, ABA-responsive protein 18 and BEL1-like homeodomain protein 1 had log2fold change above 4.0. A total of 12,836 simple sequence repeats and 4,438 single nucleotide polymorphisms were identified which can be utilized in molecular studies. CONCLUSIONS: Phyto-hormones biosynthesis-predominantly through ABA signalling, and secondary metabolism are the most potent pathways for alkalinity stress tolerance in lentil. Cultivar PDL-1 exhibited high tolerance towards alkalinity stress and can be used in breeding programmes for improving lentil production under alkalinity stress conditions.

Genome-wide association mapping reveals key genomic regions for physiological and yield-related traits under salinity stress in wheat (Triticum aestivum L.).

A genome-wide association study (GWAS) was conducted using six different multi-locus GWAS models and 35K SNP array to demarcate genomic regions underlying reproductive stage salinity tolerance. Marker-trait association analysis was performed for salt tolerance indices (STI) of 11 morpho-physiological traits, and the actual concentrations of Na+ and K+, and the Na+/K+ ratio in flag leaf. A total of 293 significantly associated quantitative trait nucleotides (QTNs) for 14 morpho-physiological traits were identified. Of these 293 QTNs, 12 major QTNs with R2 ≥ 10.0% were detected in three or more GWAS models. Novel major QTNs were identified for plant height, number of effective tillers, biomass, grain yield, thousand grain weight, Na+ and K+ content, and the Na+/K+ ratio in flag leaf. Moreover, 48 candidate genes were identified from the associated genomic regions. The QTNs identified in this study could potentially be targeted for improving salinity tolerance in wheat.

Soil salinity under climate change: Challenges for sustainable agriculture and food security.

Soil salinity is one of the major and widespread challenges in the recent era that hinders global food security and environmental sustainability. Worsening the situation, the harmful impacts of climate change accelerate the development of soil salinity, potentially spreading the problem in the near future to currently unaffected regions. This paper aims to synthesise information from published literature about the extent, development mechanisms, and current mitigation strategies for tackling soil salinity, highlighting the opportunities and challenges under climate change situations. Mitigation approaches such as application of amendments, cultivation of tolerant genotypes, suitable irrigation, drainage and land use strategies, conservation agriculture, phytoremediation, and bioremediation techniques have successfully tackled the soil salinity issue, and offered associated benefits of soil carbon sequestration, and conservation and recycling of natural resources. These management practices further improve the socio-economic conditions of the rural farming community in salt-affected areas. We also discuss emerging reclamation strategies such as saline aquaculture integrated with sub surface drainage, tolerant microorganisms integrated with tolerant plant genotypes, integrated agro-farming systems that warrant future research attention to restore the agricultural sustainability and global food security under climate change scenarios.

Genetic Dissection and Identification of Candidate Genes for Salinity Tolerance Using Axiom®CicerSNP Array in Chickpea.

Globally, chickpea production is severely affected by salinity stress. Understanding the genetic basis for salinity tolerance is important to develop salinity tolerant chickpeas. A recombinant inbred line (RIL) population developed using parental lines ICCV 10 (salt-tolerant) and DCP 92-3 (salt-sensitive) was screened under field conditions to collect information on agronomy, yield components, and stress tolerance indices. Genotyping data generated using Axiom®CicerSNP array was used to construct a linkage map comprising 1856 SNP markers spanning a distance of 1106.3 cM across eight chickpea chromosomes. Extensive analysis of the phenotyping and genotyping data identified 28 quantitative trait loci (QTLs) explaining up to 28.40% of the phenotypic variance in the population. We identified QTL clusters on CaLG03 and CaLG06, each harboring major QTLs for yield and yield component traits under salinity stress. The main-effect QTLs identified in these two clusters were associated with key genes such as calcium-dependent protein kinases, histidine kinases, cation proton antiporter, and WRKY and MYB transcription factors, which are known to impart salinity stress tolerance in crop plants. Molecular markers/genes associated with these major QTLs, after validation, will be useful to undertake marker-assisted breeding for developing better varieties with salinity tolerance.

Introgressed Saltol QTL Lines Improves the Salinity Tolerance in Rice at Seedling Stage.

Rice is a staple food crop in Asia and plays a crucial role in the economy of this region. However, production of rice and its cultivating areas are under constant threat of soil salinity. A major QTL, Saltol, responsible for salinity tolerance at seedling stage has been mapped on chromosome 1 using Pokkali/IR29 Recombinant Inbred Lines (RIL) population. The present study was aimed to incorporate Saltol Quantitative Trait Loci (QTL) in two high yielding mega rice varieties i.e. Pusa44 and Sarjoo52 through Marker Assisted Backcross Breeding (MABB). To improve the seedling stage salinity tolerance in these cultivars, we introgressed the Saltol QTL from donor parent FL478 a derivative of Pokkali. A total of three backcrosses (BC3) followed by selfing have led to successful introgression of Saltol QTL. Foreground selection at each breeding cycle was done using micro-satellite markers RM3412 and AP3206 to confirm Saltol QTL. The precise transfer of Saltol region was established using recombinant selection through flanking markers RM493 and G11a. Finally, 10 Saltol near isogenic lines (NILs) of Pusa44 and eight NILs of Sarjoo52 were successfully developed. These NILs (BC3F4) were evaluated for seedling stage salinity under hydroponic system. The NILs PU99, PU176, PU200, PU215, PU229, PU240, PU241, PU244, PU252, PU263 of Pusa44 and SAR17, SAR23, SAR35, SAR39, SAR77, SAR87, SAR123, SAR136 NILs of Sarjoo52 confirmed tolerance to salinity with low salt injury score of 3 or 5. Ratio of Na+/K+ content of Saltol NILs ranged from 1.26 to 1.85 in Pusa44 and 1.08 to 1.69 in Sarjoo52. The successfully developed NILs were further phenotyped stringently for morphological traits to estimate Phenotypic Recovery. Background selection of NILs along with parents was carried out with 50K SNP chip and recovered 94.83-98.38% in Pusa44 NILs and 94.51 to 98.31% in Sarjoo52 NILs of recurrent genome. The present study of MAB has accelerated the development of salt tolerant lines in the genetic background of Pusa44 and Sarjoo52. These NILs could be used for commercial cultivation in saline affected area.

Impact of carbon inputs on soil carbon fractionation, sequestration and biological responses under major nutrient management practices for rice-wheat cropping systems.

Major nutrient management systems for rice-wheat cropping were compared for their potential to credit organic carbon (C) to the soil, its fractionation into active (very labile, VLc; labile, Lc) and passive (less labile, LLc; non-labile, NLc) pools, and crop yield responses. A ten-year long experiment was used to study effects of: (i) no inputs (Control, O), (ii) 100% inorganic fertilizers (F) compared to reduced fertilizers inputs (55%) supplemented with biomass incorporation from (iii) opportunity legume crop (Vigna radiata) (LE), (iv) green manure (Sesbania aculeata) (GM), (v) farmyard manure (FYM), (vi) wheat stubble (WS), and (vii) rice stubble (RS). Maximum C input to soil (as the percentage of C assimilated in the system) was in GM (36%) followed by RS (34%), WS (33%), LE (24%), and FYM (21%) compared to O (15%) and F (15%). Total C input to soil had a direct effect on soil C stock, soil C fractions (maximum in VLc and LLc), yet the responses in terms of biological yield were controlled by the quality of the biomass (C:N ratio, decomposition, etc.) incorporated. Legume-based biomass inputs accrued most benefits for soil C sequestration and biological productivity.

Evaluation of cultivated and wild genotypes of Lens species under alkalinity stress and their molecular collocation using microsatellite markers.

In this study, 285 lentil genotypes were phenotyped under hydroponic and alkaline field conditions. Significant genotypic variation for alkalinity stress was observed among the six Lens species screened hydroponically and in the field having pH up to 9.1. The crucial parameters, like whole Na+ and K+ contents and the Na+/K+ ratio at 40 mM NaHCO3 were found significantly correlated with seedling survivability under hydroponics (r = -0.95, r = 0.93 and -0.97). Genotypes, ranked on the bases of seed yield, restricted uptake of Na+ with thick pith area, increased vascular bundles, less H2O2 production and low Na+/K+ ratio, were found important physio-anatomical traits for alkalinity stress tolerance. The proper regulation of Na+ uptake was found for maintaining higher K+. This relationship is probably the main factor responsible for a better mechanism for tolerance to high pH up to 9.1 in tolerant breeding lines PDL-1 and PSL-9 (cultivars) and ILWL-15, ILWL-192 and ILWL-20 (wild accessions). Based on UPGMA dendrogram, all the genotypes were clustered into four diverse groups. DMRT was implied within the group to differentiate genotypes based on phenotypic response under alkalinity stress. These results can be utilized for selecting diverse parents for developing alkalinity tolerant genotypes.