Tolerant Lines Research Articles

EXTRACELLULAR VESICLES TRANSFER RESISTANCE TO VINCRISTINE IN SONIC HEDGEHOG MEDULLOBLASTOMA

Abstract AIMS • To determine the expression patterns of specific ATP-binding cassette (ABC) transporters in medulloblastoma • To assess whether ABC transporters play a role in acquired drug resistance in SHH medulloblastoma using drug-tolerant cell line models • To assess whether extracellular vesicles transfer drug-tolerance in SHH medulloblastoma and determine the mechanism by which they do this METHOD Drug-tolerant cell lines were generated by continuous culture in drug-containing culture medium. ABC trans- porter gene and protein expression was assessed via qPCR and western blot. EVs were isolated from EV-depleted medium using size-exclusion chromatography. Nanoparticle tracking analysis was used to quantify and deter- mine size. Cytotoxicity analysis was used to determine EV-mediated transfer of resistance in the presence or absence of an ABC transporter inhibitor. RNA sequencing of EVs from matched vehicle and drug tolerant cell lines was carried out. RESULTS Analysis of drug-tolerant cell lines revealed significant increases in specific drug transporter gene expression across medulloblastoma subgroups. ABCB1 protein expression was significantly higher in drug-tolerant sonic- hedgehog (SHH) lines and inhibition of ABCB1 in a drug-tolerant SHH line abolished acquired resistance to vincristine. Cytotoxicity assays on sensitive cells, after pre-treatment with drug-tolerant EVs, showed a significant increase in vincristine resistance, implicating EVs in the transfer of resistance. CONCLUSIONS Data to date supports the hypothesis that multidrug transporter carrying extracellular vesicles may transfer their multidrug resistant phenotype to surrounding cells in medulloblastoma. We are currently testing this using inhibitors and knockout lines, in addition to RNA sequencing, with the hopes of providing new therapeutic targets to patients with medulloblastoma.

Root-hypoxia tolerance in soybean sister-lines plants indicates a better balance in energy use/dissipation and oxidative stress control

Climatic changes are leading to an increased number of flooding year by year which impacts negatively the metabolism of roots and influences the shoot metabolism which leads to a decline in soybean productivity. This can be more drastic when it is cultivated in lowland soils. Our group hypothesized that tolerant sister-line plants have more capacity to cope with oxidative stress due to better management of energy use and dissipation on photosynthesis machinery during root-flooding and recovery conditions, while in sensitive soybean sister-line the impairment of the photosynthetic use and dissipation of energy lead to an unbalanced redox state response. For that, soybean seeds from the same parents, PELBR15- 7015C (flooding tolerant) and PELBR15-7060 (flooding sensitive) were sowed and cultivated in 500 L capacity plastic containers with lowland soil simulating the field management process. At the reproductive stage, the roots were subjected to flooding for 11 days, then drained to analyze reoxygenation (3 d) and recovery (10 d). Tolerant plants have a greater ability to manage root flooding conditions compared to sensitive ones. The ability includes efficient energy use and dissipation, which minimizes the production of reactive oxygen species (ROS) and subsequent cell damage. Conversely, in sensitive sister lines, impaired electron transport chains lead to increased ROS production and damage. Upon reoxygenation and recovery, the tolerant sister lines exhibit a faster metabolism turnover, allowing them to cope more effectively with the stress on leaves and roots. While both sister lines are capable of detoxifying ROS, the tolerant sister line's superior ability to manage energy use and dissipation allows for more stable and rapid control of oxidative stress.

Impacts of salinity stress on crop plants: improving salt tolerance through genetic and molecular dissection.

Improper use of water resources in irrigation that contain a significant amount of salts, faulty agronomic practices such as improper fertilization, climate change etc. are gradually increasing soil salinity of arable lands across the globe. It is one of the major abiotic factors that inhibits overall plant growth through ionic imbalance, osmotic stress, oxidative stress, and reduced nutrient uptake. Plants have evolved with several adaptation strategies at morphological and molecular levels to withstand salinity stress. Among various approaches, harnessing the crop genetic variability across different genepools and developing salinity tolerant crop plants offer the most sustainable way of salt stress mitigation. Some important major genetic determinants controlling salinity tolerance have been uncovered using classical genetic approaches. However, its complex inheritance pattern makes breeding for salinity tolerance challenging. Subsequently, advances in sequence based breeding approaches and functional genomics have greatly assisted in underpinning novel genetic variants controlling salinity tolerance in plants at the whole genome level. This current review aims to shed light on physiological, biochemical, and molecular responses under salt stress, defense mechanisms of plants, underlying genetics of salt tolerance through bi-parental QTL mapping and Genome Wide Association Studies, and implication of Genomic Selection to breed salt tolerant lines.

Prioritization of Microsatellite Markers Linked with Drought Tolerance Associated Traits in Chickpea (Cicer arietinum L.)

Background: Being a vital source of high-quality dietary protein, chickpea is an unavoidable legume. The present investigation was performed to study the applicability of the microsatellite markers linked with drought tolerance in Indian chickpea genotypes collected from different genetic background. Methods: In Rabi 2021-22, forty chickpea genotypes including national check for drought tolerance, elite cultivars, released varieties and advanced breeding lines were screened employing forty microsatellite markers linked with drought tolerance associated traits. Results: Among forty drought tolerance related microsatellite markers, twenty-six were found to be polymorphic and produced a total of 66 alleles, with a mean of 2.5 alleles per locus. Genotype NCPGR127 had highest numbers of alleles, gene diversity and polymorphism information content tracked by genotype TR19. These genotypes may be used for selecting drought tolerant genotypes through marker assistant selection (MAS). Model-based population structure analysis clearly distinguished the drought tolerant genotypes including ICC4958, JG74, JAKI9218, JG16, JG6, JG14 and JG11. Principle coordinate analysis (PCoA) and analysis of molecular variance (AMOVA) further confirmed these results. Findings of the present investigation have a greater potential for further utilization in breeding of drought specific chickpea cultivar(s).

In Vitro Salt Stress Responses of Thai Oil Palm’s Embryogenic Callus Variety ‘SUP-PSU1’

Evapotranspiration, which includes the evaporation of water from soils, may rise as a result of climate change and rising temperatures. The outcome is that water evaporates but salt stays in the soil, raising its saltiness. The growth and development of oil palm are also affected by salt stress, but decades of time frame are required with conventional breeding due to its reproductive biological reasons and its long-time life span. However, to facilitate stress tolerance evaluation at an early stage of plant material, the in vitro selection was considered, and the evaluation process was optimized for innovating variant selection out from calluses over abiotic stress. Thus, the objectives of this research were to study the effect of concentrations of sodium chloride (NaCl) on the growth rate, electrolyte leakage (EL) and proline content of embryogenic callus (EC) of oil palm ‘SUP-PSU1’. Was also, recovery of EC growth after treating with NaCl for further evaluation to set new variant tolerant line for breeding was established. EC was treated with different concentrations of NaCl in oil palm culture medium (OPCM) supplemented with 0.1 mg L–1 3,6-Dichloro-o-anisic acid (dicamba) and 200 mg L–1 ascorbic acid (AA) for 4 weeks. The results showed that inhibition concentration at 50 % (IC50) was 149.1 mM and NaCl at high concentrations increased EL and proline content. After transferring treated EC to solidified medium without NaCl for 4 weeks, The 200 mM condition’s EC turned yellowish-brown and couldn’t withstand higher (300 and 400 mM) NaCl concentrations. The lowest growth rate was obtained with NaCl at 300 and 400 mM, and the EC entirely turned brown. So, it was judged that NaCl concentration around 300 to 400 mM can be used as a selection agent for ‘SUP-PSU1’ new variant tolerant line in oil palm tissue culture breeding condition. HIGHLIGHTS The inhibition concentration that limits the growth of embryogenic callus of oil palm ‘SUP-PSU1’ at 50 % (IC50) was 149.1 mM NaCl at high concentration resulted in an increment of electrolyte leakage (EL) and proline content The embryogenic callus of oil palm ‘SUP-PSU1’can tolerate to NaCl up to 200 mM NaCl at concentrations of 300 and 400 mM can be used as a selection agent for ‘SUP-PSU1’ new variant tolerant line in oil palm tissue culture breeding condition GRAPHICAL ABSTRACT

In-vitro selection of drought tolerant doubled haploid rice lines using polyethylene glycol (PEG)

The present study was conducted to determine the response of 55 double haploid (DH) rice lines developed for drought tolerance from the cross Swarna × IR159B in polyethylene glycol (PEG) induced drought stress under in-vitro conditions (DH lines named as double haploid rice lines-DRL). Drought stress was created using PEG-6000 at different level of external water potential. Analyzed seedling traits of DRLs showed significant differences in response to different PEG concentrations. A decrement in plant growth at seedling stage with the increase in PEG concentration was observed as expected. Among 55DRLs, 14 DRLs were found to be drought tolerant sustaining the stress level till -7.5 bar as of the tolerant checks. Further, Drought linked SSRs were also evaluated in developed rice lines. Out of 8 SSRs, RM55 (R2 value- 13.5%) and RM259 (R2 value- 13.9%) found to be exhibiting significant association with the shoot/root ratio at - 7.5 bar stress level. Out of 14 DRLs, 9 DRLs were found to be showing drought tolerant in phenotypic and genotypic screening. Hence, PEG induced stress screening method used in this study will serve as the baseline for screening of rice lines for drought tolerance at very early stage without exploitation of much resource.

Transcriptome Analysis Revealed the Potential Molecular Mechanism of Anthocyanidins' Improved Salt Tolerance in Maize Seedlings.

Anthocyanin, a kind of flavonoid, plays a crucial role in plant resistance to abiotic stress. Salt stress is a kind of abiotic stress that can damage the growth and development of plant seedlings. However, limited research has been conducted on the involvement of maize seedlings in salt stress resistance via anthocyanin accumulation, and its potential molecular mechanism is still unclear. Therefore, it is of great significance for the normal growth and development of maize seedlings to explore the potential molecular mechanism of anthocyanin improving salt tolerance of seedlings via transcriptome analysis. In this study, we identified two W22 inbred lines (tolerant line pur-W22 and sensitive line bro-W22) exhibiting differential tolerance to salt stress during seedling growth and development but showing no significant differences in seedling characteristics under non-treatment conditions. In order to identify the specific genes involved in seedlings' salt stress response, we generated two recombinant inbred lines (RILpur-W22 and RILbro-W22) by crossing pur-W22 and bro-W22, and then performed transcriptome analysis on seedlings grown under both non-treatment and salt treatment conditions. A total of 6100 and 5710 differentially expressed genes (DEGs) were identified in RILpur-W22 and RILbro-W22 seedlings, respectively, under salt-stressed conditions when compared to the non-treated groups. Among these DEGs, 3160 were identified as being present in both RILpur-W22 and RILbro-W22, and these served as commonly stressed EDGs that were mainly enriched in the redox process, the monomer metabolic process, catalytic activity, the plasma membrane, and metabolic process regulation. Furthermore, we detected 1728 specific DEGs in the salt-tolerant RILpur-W22 line that were not detected in the salt-sensitive RILbro-W22 line, of which 887 were upregulated and 841 were downregulated. These DEGs are primarily associated with redox processes, biological regulation, and the plasma membrane. Notably, the anthocyanin synthesis related genes in RILpur-W22 were strongly induced under salt treatment conditions, which was consistented with the salt tolerance phenotype of its seedlings. In summary, the results of the transcriptome analysis not only expanded our understanding of the complex molecular mechanism of anthocyanin in improving the salt tolerance of maize seedlings, but also, the DEGs specifically expressed in the salt-tolerant line (RILpur-W22) provided candidate genes for further genetic analysis.

Harnessing parent-offspring regression analysis to develop high-yielding submergence tolerant lines of Oryza sativa L.

Harnessing parent-offspring regression analysis to develop high-yielding submergence tolerant lines of Oryza sativa L.

Dittrichia viscosa Selection Strategy Based on Stress Produces Stable Clonal Lines for Phytoremediation Applications.

Dittrichia viscosa uptake and translocation of the metalloid As is not fully understood and some data are contradictory, but its adaptability to this pollutant is known and is dependent on its genetic variability. D. viscosa is not a hyperaccumulator plant, but it can grow in high-drought conditions while still producing large biomass, even tolerating significant concentrations of As3+ and As5+. In spite of these remarkable characteristics, adaptive modification of performances is not predictable in wild populations. In previous work, we established experimental clonal populations to perform a functional study on the aquaporin NIP1.1. Here, we propose a strategy to select a clonal population of D. viscosa with a defined phenotype related to As tolerance and to reduced NIP1.1 expression levels for phytoremediation applications. From the previous work, we selected four independent clones, two of them belonging to the weak population (W8 and W9) and the other two belonging to the strong population (S1 and S3). The weak and strong populations differ for a different expression ratio root/shoot of DvNip1;1 that brings a different tolerance to As presence. The stress response of the populations, revealed by the CAT enzymatic test, was statistically correlated to the clones, but not to As uptake. Performance of the selected plants on a second unrelated metallic pollutant, Cd, was evaluated, showing that Cd uptake is also independent from the tolerant phenotype. In vitro culture methods using solid media and temporary immersion bioreactors were compared to propose an optimized combined protocol. The procedure yielded propagation of genetically stable tolerant clonal lines with good uptake of As and Cd. The plants, mass-produced with the developed in vitro protocol, were able to maintain their acquired abilities and are potentially able be later applied in phytoremediation or contaminated areas' re-naturalization.

The Sweet Potato K+ Transporter IbHAK11 Regulates K+ Deficiency and High Salinity Stress Tolerance by Maintaining Positive Ion Homeostasis.

The K+ transporter KT/HAK/KUP (K+ transporter/high-affinity K+/K+ uptake) family has a critical effect on K+ uptake and translocation in plants under different environmental conditions. However, the functional analysis of KT/HAK/KUP members in sweet potatoes is still limited. The present work reported the physiological activity of a new gene, IbHAK11, in the KT/HAK/KUP family in sweet potatoes. IbHAK11 expression increased significantly in the low K+-tolerant line compared with the low K+-sensitive line following treatment with low K+ concentrations. IbHAK11 upregulation promoted root growth in Arabidopsis under low K+ conditions. Under high saline stress, transgenic lines had superior growth and photosynthetic characteristics compared with the wild-type (WT). As for IbHAK11-overexpressing plants, activation of both the non-enzymatic and enzymatic reactive oxygen species (ROS) scavenging systems was observed. Therefore, IbHAK11-overexpressing plants had lower malondialdehyde (MDA) and ROS levels (including H2O2 and O2-) compared with WT under salt-induced stress. We also found that under both low K+ and high salinity conditions, overexpression of IbHAK11 enhanced K+ translocation from the root to the shoot and decreased Na+ absorption in Arabidopsis. Consequently, IbHAK11 positively regulated K+ deficiency and high salinity stresses by regulating K+ translocation and Na+ uptake, thus maintaining K+/Na+ homeostasis in plants.

Improvement of Safflower (Carthamus tinctorius L.) for Salinity Tolerance under in vitro Condition

Aim: The primary aim of the present study was to screen the salt tolerant calli and optimization of in-vitro regeneration protocol from selected screen calli.
 Methodology: The cotyledonary leaf explants was sterilized by using 1% Bavistin, 0.1% Mercuric chloride and 70% ethanol followed by washing with distilled water. Sterilized explants were cultured on Murashige and Skoog (MS) medium supplemented with different concentration of NaCl (i.e. 0, 50mM, 100mM, 200mM, 300 mM and 400 mM) to check the salinity tolerance ability of PKV pink genotype. In vitro screening of callus was studied by morphological characters like colour and texture of callus, callus growth percentage, relative water contained, cell survivility and proline content from saline stress and unstress calli to confirm the saline tolerance pressure to regenerate the PKV Pink safflower genotype.
 Results: MS medium supplemented with 150 mM NaCl showed 50% survival of calli, whereas no growth was obtained in high concentration of NaCl. Moreover, biochemical assay like proline estimation was done for its confirmation from different NaCl stress and unstress calli. The proline accumulation found to be highest callus grown on MS media supplemented with 150 mM NaCl as compared to control. Also studied the morphological observation i.e. colour and texture of calli, callus growth percentage, relative water content and cell viability under different NaCl stress to select the saline tolerance pressure to regenerate the tolerance line in PKV Pink. The saline tolerance shoots failed to produce in vitro rooting on the standardized rooting medium. So, the different approach like higher auxin shock and grafting experiment were attempted to overcome the rooting problem. Higher auxin shock experiment failed but grafting approach found satisfactory to overcome the rooting in saline tolerance shoot and for development of saline tolerance line in PKV Pink safflower genotype.
 Conclusion: The development of abiotic stress tolerance plants found the better understanding of physiological and biochemical changes in plants under in vitro stress conditions.

Reactions of provitamin-A-enriched maize to foliar diseases under field conditions in Nigeria

Maize is a major staple food in Sub-Saharan Africa (SSA). Vitamin A deficiency index is high in Africa and could be reduced through the consumption of provitamin-A-enriched maize. However, foliar diseases such as maize streak virus, northern corn leaf blight and common rust constrain maize production in SSA. The cultivation of host-resistant varieties is the most effective approach to mitigate their effects. Therefore, maize synthetics improved for PVA carotenoids, their selection cycles and crosses as well as a commercial disease-resistant check were assessed for resistance to maize streak virus, northern corn leaf blight and common rust at hotspots in Nigeria. The foliar diseases’ effects on the agronomic performance and carotenoid content of the maize genotypes were assessed. The Genotypes differed for most agronomic traits and foliar disease resistance. Stepwise regression revealed that, although the agronomic traits determined 93% of the grain yield, each foliar disease had effect on the yield. A unit increase in maize streak virus score increased plant aspect and husk cover scores by 0.6 and 0.4, respectively, whereas an increase in common rust score decreased plant height by 16.2 cm and increased plant aspect score by 0.7. Maize streak virus and common rust decreased genotypic variability for lutein by 36.7 and 18.7%, respectively, while northern corn leaf blight decreased genotypic variability for provitamin A by 27.1%. Most of the genotypes exhibited moderate susceptibility to northern corn leaf blight. However, three selection cycles and three crosses exhibited high tolerance to maize streak virus and moderate tolerance to common rust, thus can serve as sources of PVA-enriched, maize streak virus and common rust tolerant lines.

Polyethylene glycol-induced drought stress screening of selected Philippine high-yielding sugarcane varieties

A greenhouse study was conducted to characterize the drought response of eight high-yielding sugarcane varieties at tillering stage using polyethylene glycol 6000 (PEG6000) induced drought conditions. Plant height, stalk diameter, dry matter accumulation, root characteristics, stomatal conductance, chlorophyll fluorescence, SPAD, normalized difference vegetation index (NDVI), and canopy temperature were evaluated at 2.5 months after planting after four weeks of induced drought conditions. The study aimed to determine whether 1.0% PEG treatment would be able to produce significant differences among test genotypes and use it as a basis to determine drought-tolerant and susceptible varieties. Significant differences were observed among genotypes in PEG stress treatments. PEG stress resulted in significant reductions relative to non-PEG treatment in plant height (32.1%), leaf dry matter (31.6%), and stalk dry matter (49.5%) while total root length (11.8%), root surface area (7.8%) and root volume (19.6%) have generally increased. Reduced plant height, stalk diameter, and dry matter accumulation were observed in susceptible genotypes, while potential tolerant lines maintained or exhibited less reduction in these traits. Moreover, principal component analysis suggests that stalk dry matter, stomatal conductance, chlorophyll fluorescence plant height, SPAD, canopy temperature, and NDVI, highly contributed to the overall variation in the data (41.5%). With this, vars. 2289, 1011, 2569, and 1899 were identified to be potential drought-tolerant varieties while vars. 1763 and 2155 were potential drought susceptible varieties. Screening for drought tolerance under controlled conditions using PEG-induced drought stress offers a promising approach for sugarcane breeding especially when focusing on specific drought responses during important formative stages such as tillering stage. Being able to select genotypes of interest as early as the tillering stage would significantly hasten breeding cycles and will highly benefit the efforts towards drought stress tolerance in sugarcane.

The heritability of tolerance to pathogenic fungi <i>Alternaria dauci</i> and <i>Fusarium oxysporum</i> by carrot hybrids

Relevance. Alternaria dauci, Alternaria radicina and Fusarium oxysporumare wide spread and harmful fungal diseases of carrot (Daucus carota L.) in the Russian Federation and in the world. Total losses of roots from these diseases are 35-70%. Obtaining of new varieties and hybrids resistant to these pathogens is complicated by the fact of polygenic control resistance traits to fungal diseases of Alternaria and Fusarium genus. Interaction of polygenic resistance traits with environmental factors causes the soft character of changing these traits: effects of interactions between alleles and genes are changed, the dominant effect become weaker, additive effect become stronger. So, we can say about of the tolerance to complex pathogens for that case.The goal of our study is to determine the heritability of tolerance to fungal pathogens Alternaria dauci and Fusarium oxysporum by hybrids F1 of carrot.Materials and methods. Materials of studies were 7 basic lines with different types of roots; 7 prospective hybrids F1 and mycelium of Alternaria dauci and Fusarium oxysporum with spores (for inoculation). Methods of studies were: evaluation resistance of lines and hybrids F1 (seedlings, adult plants and roots) at different types of infection backgrounds; dispersion and correlation analysis. Resistance the basic lines of carrot to fungi of Alternaria and Fusarium genus was evaluated step-by-step, using several types of artificial and natural infection backhybrids F1. Tolerant samples were selected and they were used in crossings. F1 – hybrids have been obtained and they have been evaluated at artificial and natural backgrounds.Results: 1. One tolerant male form № 1268 and 6 female forms with weak sensitivity to fungi of Alternaria and Fusarium genus were selected from basic material. They were used in crossings. hybrids F1 have been obtained. 2. Analysis the heritability of carrot resistance to fungal pathogens Alternaria dauci and Fusarium oxysporum identified, that such type of resistance inherited by father’s type. 3. Using tolerant carrot line № 1268 in crossings as the male form and 6 female forms with weak sensitivity to fungal pathogens Alternaria dauci and Fusarium oxysporum increased significantly the percent of tolerant plant in 3 F1 – hybrid population under artificial infection on provocative infection background.

Evaluation of chickpea (Cicer arietinum L.) in response to salinity stress

Soil salinity is a severe and expanding soil degradation problem that affects 80 million ha of arable lands globally. Chickpea (Cicer arietinum L.) is very sensitive to saline conditions; the most susceptible genotypes may die in just 25 mM NaCl in hydroponics. Approximately 8–10% yield loss in chickpea production is estimated due to salinity stress. However, it is still not established why chickpea is so susceptible to salt affection. Salinity (NaCl) impedes germination of seeds, though chickpea varieties considerably differ from one another in this respect. Some chickpea genotypes are more tolerant in the stage of germination, tolerating even 320 mM NaCl. The reasons of this variation are unrevealed; there is a shortage of knowledge about the germination abilities of chickpea genotypes in saline conditions. Nevertheless, the effect of salt stress on vegetative growth can be analysed in hydroponics, in pot or field conditions, regardless the experimental environment, the ranking of genotypes regarding salt resistance is coherent. Chickpea genotypes can be different in their ability to retain water, maybe under salt affection; the more salt tolerant lines can maintain higher water content in the shoots, while the more sensitive ones cannot. The identification of salt tolerant chickpea landraces based on developing genetic variability is a suitable strategy to combat against salinity problems arising in arid and semi-arid areas.

Morphophysiological Diversity and Haplotype Analysis of Saltol QTL Region in Diverse Rice Landraces for Salinity Tolerance

Rice is sensitive to salinity stress at both the seedling and reproductive stages. The present study used 145 rice genotypes comprising of 100 landraces and 45 advanced breeding lines collected from different regions of India. These genotypes were evaluated in hydroponics under control [electrical conductivity (ECe) ∼1.2 dS/m] and saline (ECe ∼10.0 dS/m) environments along with susceptible (IR29) and tolerant (FL478) checks. The stress susceptibility index for eight morphophysiological traits was estimated. Analysis of variance showed significant differences among the genotypes for all the parameters studied in control, stress and relative stress conditions. We identified 3 landraces (Kuttimanja, Tulasimog and IET-13713I) as tolerant and 14 lines as moderately tolerant to salt stress. Strong correlations in the morphological (root and shoot lengths) and physiological traits (shoot Na+, Ca2+ and Mg2+ contents, and Na+/K+ ratio) were observed under all the conditions. The hierarchical cluster analysis grouped the genotypes into five clusters, among which cluster II comprised salt-tolerant lines. Haplotyping of Saltol region using 11 simple sequence repeat markers on 17 saline tolerant and moderately tolerant lines was conducted. Markers AP3206F, RM10793 and RM3412b, located close to SKC1 gene (11.23‒12.55 Mb), displayed diverse allelic variations and they were not related to the FL478 type. In this region, tolerant lines like Kuttimanja, IET-13713I and Tulasimog have new alleles. As a result, these lines may be suitable candidates for novel genomic regions governing rice salinity tolerance. Salt-tolerance ability of Kuttimanja, Tulasimog and IET-13713I was validated in two years in three salinity stress environments. These promising lines can be used in breeding programs to broaden the genetic base of salinity tolerance in rice, and it may help to dissect key genomic regions responsible for salinity tolerance.

Monocot crop-aphid interactions: Plant resilience and aphid adaptation.

Globally, aphids cause immense economic damage to several crop plants. In addition, aphids vector several plant viral diseases that accelerate crop yield losses. While feeding, aphids release saliva that contains effectors, which modulate plant defense responses. Although there are many studies that describe the mechanisms that contribute to dicot plant-aphid interactions, our understanding of monocot crop defense mechanisms against aphids is limited. In this review, we focus on the interactions between monocot crops and aphids and report the recently characterized aphid effectors and their functions in aphid adaptation to plant immunity. Recent studies on plant defense against aphids in monocot-resistant and tolerant crop lines have exploited various "omic'' approaches to understand the roles of early signaling molecules, phytohormones, and secondary metabolites in plant response to aphid herbivory. Unraveling key regulatory mechanisms underlying monocot crop resistance to aphids will lead to deeper understanding of sap-feeding insect management strategies for increased food security and sustainable agriculture.

Evaluation of wheat (Triticum aestivum L.) lines for drought tolerance in Kyrgyzstan

The study was carried out to explore drought stress indices in F4 hybrid generations of Triticum aestivum L. to select drought stress tolerant lines for rainfed areas of Kyrgyzstan. Wheat is the main food crop in Kyrgyzstan. There are about 0.3 million ha allotted for wheat, more than half of these sown areas (0.2 million ha) are in rainfed farming zones, where the amount of precipitation rarely exceeds 300-400 mm per year. The study was conducted in 2019 at the experimental field of Agricultural Faculty of Kyrgyz-Turkish Manas University. Eighteen hybrid lines of spring wheat and two released varieties (standard) were evaluated under irrigated and non-irrigated conditions. The results of the study show that the mean grain yield of evaluated lines under stress condition as compared to non-stressed condition was decreased by 51.72%. The analysis of correlation coefficient indicated that the productivity of lines under both conditions highly depends from their stress tolerance indexes (STI) (0.769 to 0.928). Tolerance index (TOL) and stress susceptibility index (STI) were negatively correlated (-0.411 to -0.813) with yield of genotypes under stress condition (YS). The correlation between yield stability index (YSI) and yield of genotypes under stress condition (YS) was strongly and highly positive (1.000). Based on provided analysis, Line-1, Line-3, Line-5, Line-12, Line-13, Line-14 and Line-15 were selected as potential genotypes to cultivate in drought areas of Kyrgyzstan and can be used as drought tolerance genetic resources in crop improvement programs. Keywords: Correlation; Drought tolerance; Hybrid lines; Stress tolerance indices; Triticum aestivum L.

Genetic Divergence Study in Different Rice (Oryza sativa L.) Genotypes under Irrigated and Drought Stress Condition

Thirty rice genotypes were evaluated to study genetic divergence under irrigated and drought stress conditions in randomized block design at Bagusala farm, M. S. Swaminathan School of Agriculture, CUTM, Odisha, during summer 2019. The main objective of this experiment was to identify reproductive phase drought tolerant genotypes through study the effect of drought stress on yield, yield attributing and biochemical traits performance of selected genotypes using Mahalanobis D2 statistics. Set of 30 genotypes were grouped in to five and nine clusters under irrigated and drought situation. Under irrigated conditions cluster-Ⅰ was largest cluster with 22 genotypes followed by cluster-Ⅱ includes 5 genotypes cluster-Ⅲ, IV and V each consisted with only one genotype. Under drought condition, genotypes were grouped into nine different clusters, cluster-Ⅰ was the largest cluster involving 20 genotypes followed by cluster-Ⅱ having 3 genotypes whereas, cluster-Ⅲ, IV, Ⅴ, Ⅵ, Ⅶ, Ⅷ and Ⅸ were recorded with single genotype. The maximum intra cluster distances under irrigated conditions were found in cluster- Ⅱ (27111.9) followed by cluster-Ⅰ (17587.7). Whereas, in case of stress cluster-Ⅱ had maximum distance (21110.9) fallowed by cluster-Ⅰ (17957.8). Under irrigated maximum inter-cluster distances recorded between cluster-Ⅱ and Ⅴ (62310.8) followed by cluster-Ⅳ and Ⅴ (57656.0). In case of stress maximum inter cluster distances recorded between cluster -Ⅱ and Ⅶ (69865.5) fallowed by cluster- Ⅷ and Ⅸ (67848.9), cluster-Ⅱ and Ⅸ (65239.2). Under irrigate conditions highest manifestation towards genetic divergence was exhibited by chlorophyll followed by plant yield, 1000 grain weight, proline, number of spikelets, carbohydrates, grain weight, phenols, panicle length, panicle weight, flavonoids, number of filled grains, plant height and number of tillers. In case of drought stress, maximum percentage contribution towards to the genetic divergence was observed for Proline followed by carbohydrates, plant height, plant yield, grain weight, chlorophyll, number of spikelets, flavonoids, 1000grain weight, filled grains, phenols, panicle weight, panicle length and number of tillers, while other trait like root length did not contribute to the total divergence. The genotypes grouped under cluster Ⅰ, Ⅲ, Ⅴ, Ⅷ namely MTU1010, MTU1075, MTU1224, RNR2465 and Manipur black rice exhibited maximum drought tolerance under stress conditions. These genotypes can be used as the donor parents for development of drought tolerant lines in crop improvement programme.

Evaluation of F6 RILs for Drought Tolerance in Green Gram [Vigna radiata (L.)

An experiment was conducted at the experimental plot of College of Agriculture, Hassan, Karnataka, India during summer, i.e. January–April, 2018 with an objective to screen F6 RILs for drought tolerance using Augmented Randomized Block Design with 152 RILs, two parental lines and 5 check entries under drought stress condition. Thes F6 RILs are derived from cross between drought tolerant line VGG10-010 and drought susceptible AKL-225. Drought condition was imposed by withholding irrigation 25 days after sowing. The experiment was conducted in summer season, there were no unpredicted rains during the entire cropping period, hence the drought condition was effectively imposed. Analysis of variance (ANOVA) revealed highly significant mean squares attributable to F6 RILs for all the traits under investigation. Mean squares attributable to ‘RILs vs check entries’ were significant for all the traits except for harvest index and relative water content. The results suggest significant differences among the F6 RILs. The RILs as a group differed significantly for all of the traits under investigation, similarly, check entries as group differed significantly for all the traits except for harvest index which revealed high significant differences among 152 F6 RILs for yield, yield component traits and also for drought tolerance traits. Assessment of genetic variability in RILs will help in identifying best transgressive RILs and will ultimately decide the success of plant breeding programmes. Selection among straight RILs is effective only if trait is controlled by higher heritability, hence assessment of genetic variability assumes lot of importance.