Breeding For Salinity Tolerance Research Articles

Mapping novel QTLs for tolerance to salt stress at the late vegetative stage in durum wheat (Triticum durum L.)

Salt stress adversely affects the global durum wheat productivity. Breeding for salinity tolerance is an effective approach to improve crop production under saline conditions provided it is based on a good understanding of the genetic control of salinity tolerance. The present study was conducted, at the university of Tsukuba (in 2014), with the objective of mapping QTLs conferring salt tolerance in F2:3 populations of durum wheat derived from a cross between Razzek (salt sensitive variety) and Saragolla (salt tolerant variety). Two QTLs for salt tolerance were detected on chromosome 4B and 5B conferring the proportion of dead leaves with major effects. These two QTLs, which explained 68% of total phenotypic variation of %DL are an ideal candidate for Marker Assisted Selection (MAS) in wheat breeding programs and selection strategies to increase wheat production under saline conditions in order to meet the increasing global demand.

Trait based assessment in seedling stage of rice for salinity tolerance

Breeding for salinity tolerance is the need of the hour and identifying the potential donors and sources is very crucial. Hence, screening for the genotypes or lines by assessing the physiological and morphological traits are vital for identifying the tolerant genotypes. The lines identified in this study can be used for trait-based breeding for improving salinity tolerance in rice.

EVALUATION OF WHEAT GENOTYPES FOR SALINITY TOLERANCE BASED ON AGRONOMIC TRAITS

Salinity stress is one of the important constraints to wheat (Triticum aestivum L.) production globally. Breeding for salinity tolerance using novel genetic resources is an important mitigation strategy. This study aimed to identify and select the best wheat genotypes that are tolerant to salinity stress and provide them to researchers and wheat breeders for more intense evaluation and screening. Twenty two wheat genotypes, as well as two commercial cultivars, were regenerated and evaluated for salinity tolerance. Highly significant effects were detected for the measured traits for years, genotypes and treatment under normal and salinity stress conditions over all the two years. Interaction between treatments and genotype and interaction between genotypes and years were highly significant for all studied characters overall the two years and conditions, except plant height. Genotypes 13, 14 and Giza 168 showed the highest grain yield (ton/ha) under normal soil over two seasons, Also, genotypes 19, 20 and Giza 168 showed the highest grain yield (ton/ha) under salinity soil. The highest SSI value was detected for genotype 14, followed by genotypes 15 and 10 which had the highest values. Based on STI, MP and GMP indices, Giza 168, genotypes 19, 7 and 21 had the highest values. Grain yield under normal conditions (YP) was significantly and positively correlated with an STI, MP, GMP, TOL and SSPI. Grain yield under salt-stressed (YS) was significantly and positively correlated with an STI, MP, GMP, YSI, YI and HM. These results suggest that indices, STI, MP and GMP were able to identify high-yielding wheat genotypes under both normal and salt-stressed conditions. Frist PC accounted for about 7.42% of the variation in salt tolerance indices and the second PC for 3.57% by using biplots genotypes 20, 19 and Giza 168 were identified as the most stable high yielding genotypes under salinity stress.

Evaluation and screening of elite wheat germplasm for salinity stress at the seedling phase.

Salinity is one of the most important constraints for global cereal production, and breeding for salinity tolerance is a challenge. The limited gene pools, merged information regarding osmotic stress/tissue tolerance mechanism(s) including the accumulation of Na+ , over-stressed on the Na+ exclusion mechanism, and inadequate suitable screening methods further weaken the progress. In the present study, an attempt was made to evaluate the salt tolerance in Triticum aestivum lines using the membership function value (MFV) of certain traits viz., the root and shoot length (RL & SL), shoot and root fresh weight (SFW & RFW), shoot and root dry weight (SDW & RDW) and germination percentage (GP). This study screened 314 wheat lines (278 linked top cross population [LTPs] and 36 normal wheat cultivars) under lab conditions to evaluate their salt tolerance. A positive, and the highest, correlation coefficient was recorded between salt tolerance index (STI) of SL and the STI of RL.0.11 highly salt tolerant (HST), 59 salt tolerant (ST), 100 moderately salt tolerant (MST), 137 salt sensitive (SS), and seven highly salt sensitive (HSS) were observed with a distance of 2.2 between each category. The R-square value was maximum (0.836) between the STI of SFW and the mean MFV, which can be used as the most reliable trait for the salinity tolerance in T. aestivum at the germination phase. Wheat tolerant lines had higher tolerance to salt stress in comparison with the used normal wheat cultivars were detected at the seedling stage.

Improvement of Rice Breeding for Salinity Tolerance

Rice is one of the most significant food crop of the world. The production of rice is the second-highest in the world. Salinity is a serious constraint to increase rice production worldwide. Review of recent efforts achieved towards rice breeding for salinity tolerance has a paramount importance beside for rice production improvement in Ethiopia. Rice is a relatively new crop to Ethiopia; however, the crop is relatively well adapted to different parts of the country. Salinity is a problem of many irrigated, arid and semi-arid areas of the world where rain fall is insufficient to leach out salts from the root zone. Typical symptoms of salt injury in rice are stunted growth, leaf rolling, white leaf tip, white blotches in the leaf blade, drying of the older leaves and poor root growth. The main mechanisms of salt tolerance are control of salt uptake, reducing damage under excessive ion uptake and osmotic adjustment. The three major breeding approaches for salinity tolerant varietal development are conventional breeding, marker assisted selection and genetic engineering. Conventional rice breeding approaches exercised for thousands of years. But, the progress is slow, due to the time consuming process, the quantitative nature of most agronomic traits make difficulties in genotypes selection. However, modern breeding is more precise and efficient and easily identify undesirable genes that can be eliminated in future generations. In rice, markers like RAPDs, AFLPs, ISSRs and SSRs have been used. Among these DNA markers, SSRs is highly preferable for gene tagging and mapping efforts. The development of salt-tolerant variety by transgenic way needs more investigation. To date, transgenic salt tolerant variety has not yet reached at farmers’ field. In Ethiopia a little beat was done to identify rice genotypes adaptable to adverse saline soil conditions. From here on, more research findings highly crucial for the development of salinity tolerant rice varieties in the country. Therefore, it is a good opportunity for rice breeders to develop salt tolerant high yielding varieties in Ethiopia. Keywords : Conventional breeding, Genetic engineering, Marker-assisted selection, Rice, Salt tolerance DOI: 10.7176/JEES/10-5-02 Publication date: May 31 st 2020

Salt Tolerance Associated With Molecular Markers in Alfalfa

Background: Breeding for salinity tolerance in open-pollinated crops depends on broad genetic variation in order to select for vigorous plants under salinity stress. Objective: To compare the yield of some local alfalfa cultivars under saline and non-saline soils and to develop molecular genetic markers associated with salt tolerance using RAPD and ISSR analysis, thereby providing a basis for alfalfa salt-tolerance breeding and research. Methods: A two years field trial was carried out during 2013/14 and 2014/15 in Galbana Village at Sahl El-Tina site., North Sinai Governorate with 13 cuts after establishing period. Three local parental cultivars, nine selected populations for salt stress under different stress levels (three initial EC’s: 8.73, 10.63 and 12.43 dSm-1), a new tolerant pop, and three exotic varieties were included in the experiment under initial EC’s (10.83). Results: Under Egyptian conditions, local cultivars: Siwa and Ismaelia were qualified as more adapted to salinity stress conditions than the exotic cultivars. New tolerant pop. ranked as the top yielding across all tested parental populations followed by Siwa and Ismaelia tolerant selected populations. New valley population had the lowest fresh, dry and protein yield overall studied populations. The tolerant selected populations were out yielded than their parental cultivars. A total of 16 alfalfa populations were analyzed at the molecular level to develop molecular markers associated with salt tolerance using seven RAPD and five ISSR primers. All primers succeeded to generate reproducible polymorphic DNA products. RAPD primers produced eight positive specific markers and six negative specific markers for salt tolerance in alfalfa population Sinai-1, while ISSR primers produced 12 positive specific markers and six negative specific markers for salt tolerance in alfalfa. The dendrograms were generated using pooled RAPD, ISSR, and the combined analysis of their data divided the alfalfa populations into two main clusters. The first cluster consisted of population Sinai 1 alone, while the second one contains all other evaluated populations. Conclusion: The new tolerant pop. could be considered as a new promising population and more adapted to salt stress.

Comparative effect of salinity on growth, grain yield, water use efficiency, δ13C and δ15N of landraces and improved durum wheat varieties

Supplemental irrigation with low-quality water will be paramount in Mediterranean agriculture in the future, where durum wheat is a major crop. Breeding for salinity tolerance may contribute towards improving resilience to irrigation with brackish water. However, identification of appropriate phenotyping traits remains a bottleneck in breeding. A set of 25 genotypes, including 19 landraces and 6 improved varieties most cultivated in Tunisia, were grown in the field and irrigated with brackish water (6, 13 and 18dSm−1). Improved genotypes exhibited higher grain yield (GY) and water use efficiency at the crop level (WUEyield or ‘water productivity’), shorter days to flowering (DTF), lower N concentration (N) and carbon isotope composition (δ13C) in mature kernels and lower nitrogen isotope composition (δ15N) in the flag leaf compared with landraces. GY was negatively correlated with DTF and the δ13C and N of mature kernels and was positively correlated with the δ15N of the flag leaf. Moreover, δ13C of mature kernels was negatively correlated with WUEyield. The results highlight the importance of shorter phenology together with photosynthetic resilience to salt-induced water stress (lower δ13C) and nitrogen metabolism (higher N and δ15N) for assessing genotypic performance to salinity.

Genetic diversity and association mapping for salinity tolerance in Bangladeshi rice landraces

Breeding for salinity tolerance using Bangladeshi rice landraces and understand genetic diversity has been limited by the complex and polygenic nature of salt tolerance in rice genotypes. A genetic diversity and association mapping analysis was conducted using 96 germplasm accessions with variable response to salt stress at the seedling stage. These included 86 landraces and 10 indica varieties and lines including Nona Bokra, from southern Bangladesh. A total of 220 alleles were detected at 58 Simple Sequence Repeat (SSR) marker loci randomly distributed on all 12 rice chromosomes and 8 Sequence Tagged Site (STS) markers developed for genes SKC1, DST, and SalT. The average gene diversity was 0.5075 and polymorphism information content value was 0.4426, respectively. Cluster analysis revealed that 68 and 21 accessions were clustered into 2 distinct groups, possibly corresponding to indica and japonica groups, respectively and the remaining 7 landraces were classified as an admixed group. In addition to Wn11463, the STS marker for SKC1, RM22418 on Chr. 8 was significantly associated with salinity tolerance, at the location of a QTL detected in previous studies. Our findings of favorable alleles associated with salinity tolerance in Bangladeshi rice landraces, as well as the development of STS markers for salt tolerance genes, will be helpful in future efforts to breed salinity tolerance in rice.

Evaluation of salinity tolerance index of sunflower in Hetao Irrigation District

Soil salinization is a vital non-biological factor restricting crops yield and quality improvements across the world. The most effective and economic way of exploiting saline soils has been breeding and planting salt-tolerant species. Yet the lack of reliable, inexpensive and convenient screening method has limited progress in salt-tolerant breeding programs. Screening the applicability of different salt-intolerant indexes of cultivar under different salt stresses was critical for providing requisite scientific evidence of breeding salt-tolerant species and molecular marker in selective breeding. In this paper, the applicability of different salinity tolerance indexes of sunflower was screened. This laid the scientific relevance of salinity tolerance breeding and marker-assisted selection. To determine salinity tolerance indexes of sunflower in Hetao Irrigation District, the main local cultivar ‘LD 5009' was cropped and observed in fourteen representative fields over a period of two years. The fields included non-saline, mild-saline, saline and severe-saline zones. Twelve indexes, including yield, biomass, plant height, leaf area index, face plate diameter, SOD activity and contents of leaf chlorophyll, proline, Na+ and K+ were analyzed in response to salinity conditions and indexes which reduced with increased soil ECe selected. Nonlinear least squares numerical approximation method was used to establish an S-shaped salinity tolerance function which reflected the relationship between salinity tolerance indexes and soil ECe in different layers. The results indicated that yield, biomass, plant height, leaf area index, disc diameter, and leaf and stem K+ contents decreased with increasing soil salinity. The coefficient of determination of salinity tolerance function between biomass and ECe in the 0-20 cm soil layer was highest. There was no obvious impact of salinity on chlorophyll content. Under salinity conditions, Na+content gradually increased, while proline content and SOD activity increased followed by a decrease. In conclusion, this study verified the suitability of biomass as a key index of sunflower salinity tolerance analysis in Hetao Irrigation District.

Detection of QTLs associated with salinity tolerance in durum wheat based on association analysis

Salinity is globally a major constraint for crop production. Breeding for salinity tolerance is an effective approach to improve crop production and productivity under saline conditions provided it is based on a good understanding of the genetic control of salinity tolerance. This study deals with mapping QTLs for salinity tolerance in durum wheat (Triticum durum) by association analysis using SSR markers. A total of 119 varieties were treated in 100 mM of NaCl solution and the salinity tolerance indices (STI) for several traits were calculated as parameters to assess salinity tolerance. Among the traits assessed, the increased proportion of dead leaves (%DL) was the most suitable parameter for assessment of salinity tolerance in durum varieties at early vegetative stages because of a broader range of variation among varieties and narrower range of variation within varieties compared to other traits. The QTL associated with salinity tolerance using %DL as a parameter was detected on chromosome 4B. An additional 11 QTLs associated with seven parameters using STI of other traits were detected on chromosomes 3A, 5A, 5B, 6A and 7A.

Breeding for Salinity Tolerance in Mungbean

A experiment was performed at the Experim ntal Farm, Department of Genetics and Plant Breeding, Faculty of Agriculture, Annamalai University, Chidambaram, during the period from 06 January 2010 to 08 January 2011 to observe the response of eight parents viz., LGG 450, VRMGG Local, LGG 460, EC 30072, VRMGG 1, LGG 410, PMB 27 and VBN 1 and five hybrids namely LGG450/LGG410, VRMGG Local/PMB27, LGG460/PMB27, EC30072/PMB27 and VRMGG1/VBN1 under different salt stress (control, 4 ds m-1 (deci-Siemen per meter) and 8 ds m-1). The experiment was laid out following randomized block design where each treatment was replicated three times.All biometric characters such as number of branches plant-1, number of clusters plant-1, Number of pods plant-1, 100 seed weight, seed yield plant-1 and leaf area index; biochemical characters and biophysical characters namely total chlorophyll content, nitrate reductase activity, photosynthetic rate, transpiration rate and stomatal conductance were reduced with the increase of salinity levels as compared to control. All the hybrids recorded higher levels of salinity tolerance for all the characters compared to their respective parents except for transpiration rate and stomatal conductance. Interaction effect between the genotypes and salinity levels appeared significant for most of the studied characters. From the study it can be opined that salt stress reduced all the parameters under different salinity levels. Again among the parents and hybrids, VRMGG1/VBN1 was found as relatively salt tolerant.

Identification of salt-tolerant QTLs with strong genetic background effect using two sets of reciprocal introgression lines in rice

Effect of genetic background on detection of quantitative trait locus (QTL) governing salinity tolerance (ST) was studied using two sets of reciprocal introgression lines (ILs) derived from a cross between a moderately salinity tolerant japonica variety, Xiushui09 from China, and a drought tolerant but salinity susceptible indica breeding line, IR2061-520-6-9 from the Philippines. Salt toxicity symptoms (SST) on leaves, days to seedling survival (DSS), and sodium and potassium uptake by shoots were measured under salinity stress of 140mmol/L of NaCl. A total of 47 QTLs, including 26 main-effect QTLs (M-QTLs) and 21 epistatic QTLs (E-QTLs), were identified from the two sets of reciprocal ILs. Among the 26M-QTLs, only four (15.4%) were shared in the reciprocal backgrounds while no shared E-QTLs were detected, indicating that ST QTLs, especially E-QTLs, were very specific to the genetic background. Further, 78.6% of the M-QTLs for SST and DSS identified in the reciprocal ILs were also detected in the recombinant inbred lines (RILs) from the same cross, which clearly brings out the background effect on ST QTL detection and its utilization in ST breeding. The detection of ILs with various levels of pyramiding of nonallelic M-QTL alleles for ST from Xiushui09 into IR2061-520-6-9 allowed us to further improve the ST in rice.

Large variation in salinity tolerance in chickpea is explained by differences in sensitivity at the reproductive stage

Salinity is an ever-increasing problem in agriculture worldwide, especially in South Asia (India, Pakistan) and Australia. Improved genotypes that are well adapted to saline conditions are needed to enhance and sustain production in these areas. A screening of 263 accessions of chickpea, including 211 accessions from ICRISAT's mini-core collection (10% of the core collection and 1% of the entire collection), showed a 6-fold range of variation for seed yield under salinity (1.9 L of 80 mM NaCl per 7.5 kg Vertisol), with several genotypes yielding 20% more than a previously released salinity tolerant cultivar. The range of variation in yields under salinity was similar in both kabuli and desi chickpeas, indicating that breeding for salinity tolerance can be undertaken in both groups. A strong relationship ( r 2 = 0.50) was found between the seed yield under salinity and the seed yield under a non-saline control treatment, indicating that the seed yield under salinity was explained in part by a yield potential component and in part by salinity tolerance per se. Seed yields under salinity were therefore computed to separate the yield potential component from the residuals that accounted for salinity tolerance per se. Among the genotypes evaluated, desi genotypes had higher salinity tolerance than kabuli genotypes. The residuals were highly correlated to the ratio of seed yield under salinity to that of the control, indicating that both parameters can be used to assess salinity tolerance. A similar ratio was calculated for shoot dry weight at 50 days after sowing. However, no significant correlation was found between the shoot dry weight ratio and the yield ratio, indicating that differences in salinity tolerance among genotypes could not be inferred from measurements in the vegetative stage. The major trait related to salinity tolerance was the ability to maintain a large number of filled pods, whereas seed size was similar in tolerant and sensitive genotypes. Salinity tolerance was not related to the shoot Na + or K + concentrations.