Genome-wide association analysis of cotton salt stress response-related sites

Soil salinization is the main abiotic stress factor affecting agricultural production worldwide, and salt stress has a significant impact on plant growth and development. Cotton is one of the most salt-tolerant crops. Its salt tolerance varies greatly depending on the variety, growth stage, organs, and soil salt types. Therefore, the selection and utilization of excellent salt-tolerant germplasm resources and the excavation of excellent salt-tolerant salt and salt resistance genes play important roles in improving cotton production in saline-alkali soils. In this study, we analysed the population structure and genetic diversity of 144 elite Gossypium hirsutum cultivar accessions collected from around the world, and especially from China. Illumina Cotton SNP 70K was used to obtain genome-wide single-nucleotide polymorphism (SNP) data for 149 experimental materials, and 18,432 highly consistent SNP loci were obtained by filtering. PCA (principal component analysis)indicated that 149 upland cotton materials could be divided into 2 subgroups, including subgroup 1 with 78 materials and subgroup 2 with 71 materials. Using the obtained SNP and other marker genotype test results, under salt stress, the salt tolerance traits 3d_Germination_potential, 3d_Bud_length_drop_rate, 7d_Germination_rate, 7d_Bud_length_drop_rate, 7d_Germination_weight, 3d_Bud_length, 7d_Bud_length, relative_germination_potential, Relative_germination_rate, 7d_Bud_weight_drop_rate, Salt tolerance index 3d_Germination_potential_index, 3d_Bud_length_index, 7d_Bud_length_index, 7d_Bud_weight_index, and 7d_Germination_rate_index were evaluated by genome association analysis. A total of 27 SNP markers closely related to salt tolerance traits and 15 SNP markers closely related to salt tolerance index were detected. At the SNP locus associated with the traits of the bud length decline rate at 7 days, alleles Gh_A01G0034 and Gh_D01G0028 related to plant salt tolerance were detected, and they are related to intracellular transport, membrane microtubule formation and actin network. This study provides a theoretical basis for the selection and breeding of salt-tolerant upland cotton varieties.

The Effect of Salicylic Acid on the Performances of Salt Stressed Strawberry Plants, Enzymes Activity, and Salt Tolerance Index

The influence of salicylic acid (SA) on growth, yield, fruits’ quality and enzymes’ activities was monitored in strawberry plants cv. Camarosa grown under salinity stress via two pot experiments in two successive years of 2018 and 2019. The examined concentrations of SA were 30, 60, and 90 ppm, which foliary applied in addition to control (sprayed with water), while the used levels of salinity were 20, and 40 mM as NaCl as irrigation application in addition to control (without salinity). The results showed a significant effect of salinity at 40 mM where the mean values of shoot fresh and dry weights, chlorophyll, leaves’ NPK, yield plant−1, yield ha−1, and fruits’ ascorbic acid were significantly decreased. However, the 40 mM salinity resulted in a significant increase in leaves’ content of Na and proline as well as catalase (CAT) and peroxidase (POD) enzymes’ activity and the fruits’ TSS and acidity. The application with 90 ppm SA was found to be the most significant positive treatment for all of the studied characters except the Na leaves’ content. Regarding tolerance index percentages (STI%), the high values of CAT, POD, and proline referred to the ability to use them as indicators for strawberry salinity response in other physiological and plant breeding studies. The findings of this study suggest that the 90 ppm SA foliar application can ameliorate the negative effect of salinity on the growth of strawberry cv. Camarosa.

Transcriptional profiling of two contrasting genotypes uncovers molecular mechanisms underlying salt tolerance in alfalfa

Alfalfa is an important forage crop that is moderately tolerant to salinity; however, little is known about its salt-tolerance mechanisms. We studied root and leaf transcriptomes of a salt-tolerant (G03) and a salt-sensitive (G09) genotype, irrigated with waters of low and high salinities. RNA sequencing led to 1.73 billion high-quality reads that were assembled into 418,480 unigenes; 35% of which were assigned to 57 Gene Ontology annotations. The unigenes were assigned to pathway databases for understanding high-level functions. The comparison of two genotypes suggested that the low salt tolerance index for transpiration rate and stomatal conductance of G03 compared to G09 may be due to its reduced salt uptake under salinity. The differences in shoot biomass between the salt-tolerant and salt-sensitive lines were explained by their differential expressions of genes regulating shoot number. Differentially expressed genes involved in hormone-, calcium-, and redox-signaling, showed treatment- and genotype-specific differences and led to the identification of various candidate genes involved in salinity stress, which can be investigated further to improve salinity tolerance in alfalfa. Validation of RNA-seq results using qRT-PCR displayed a high level of consistency between the two experiments. This study provides valuable insight into the molecular mechanisms regulating salt tolerance in alfalfa.

Responses of seed germination, seedling growth under salinity stresses and variability for phenotypic traits in Tossa Jute (Corchorus olitorius L.)

Salinity is a serious abiotic stress to Jute and other crop cultivation at saline regions in the world. No salt tolerant Tossa Jute (Corchorus olitorius L.) variety was developed in Bangladesh. Hence, six Tossa Jute accessions were investigated at germination stage against six concentration levels (0.00 or d.H2O, 8.0, 10.0, 12.0, 14.0 and 16.0 dS m-1) of salt (NaCl) using RCB design at Bangladesh Jute Research Institute (BJRI) during March-July, 2020. Jute seeds collected from Gene Bank of BJRI were allowed to germinate under laboratory condition. Seed germination rate was adversely affected as well as delay in germination was prolonged with increasing the salt concentration. In control, seeds were germinated up to 14.0 dS m-1 salt solution. Among six genotypes, Acc. 1141 and Acc. 3801 showed the highest germination rate (86.67 %); Acc. 3801 gave maximum root length (17.0 mm), dry biomass (6.37 mg); and Acc. 1089 showed higher shoot length (10.0 mm), fresh weight (43.93 mg) and salt tolerance index (60.69 %) under 14.0 dS m-1 level. Higher relative salt harm rate (7.14 %) was observed in both Acc. 1141 and Acc. 3801 under 14.0 dS m-1 salinity indicating highly tolerance to salinity. Acc. 3801 and Acc. 1141 were found good for germination under salt stresses; Acc. 3801, Acc. 1089 for fiber yield and salt tolerance; Acc. 3801 and Acc. 1407 for higher fiber yield. Acc. 3801 was found good for salt tolerance and fiber yield content. The genotypes with good desirable characters would be used as breeding materials to develop high yielding salt tolerant Tossa Jute variety.

Response of three tossa jute (Corchorus olitorius L.) cultivars produced in Benin to salinity stress at germination and young plant stages

The response of three tossa jute cultivars Ordinaire, 5-Doigts and Acc : Sud 2 to salt stress was evaluated at germination and young plant stages. Five NaCl concentrations: 0; 30; 60; 90 and 120 mM NaCl were used. Seeds were submitted to NaCl in petri dishes and germination was checked every day during thirty days in a completely randomized design with four replicates. Four-week old plants were submitted in pots to the same five NaCl concentrations by irrigation every two days for two weeks in screen house. NaCl reduced seed germination rate in all cultivars from day 2 to day 30 and the germination index. At the end of the 30 days, salt stress reduced the final germination percentages with a significant difference among cultivars: cultivar 5-doigts was the least affected than the two other cultivars. Salt effect caused a reduction of young plant growth whatever the growth parameter considered with a significant difference among cultivars. The growth of cultivar Acc:Sud 2 was more affected by salt stress with the lowest salt tolerance index whereas that of cultivar Ordinaire was the least affected with the highest salt tolerance index. Thus, cultivar 5-Doigts appeared as the most resistant to salt stress at germination stage among the three cultivars; whereas cultivar Ordinaire followed by 5-Doigts was the most salt resistant at young plant stage.

Differential Responses on Chlorophyll Content, Osmolyte Accumulation and Membrane Damage Parameters under Salinity Stress on Tolerant and Susceptible Genotypes of Groundnut

Salinity can affect different physiological activity of plant in various ways. A controlled study was conducted to screen 26 genotypes of groundnut under 200mM NaCl salinity stress. The salt tolerance index or STI of the genotypes ranged from 47.57% to 96.40%. Out of all the genotypes KDG-197 (STI= 96.40%) was found to be the most tolerant under a salinity stress of 200 mM NaCl and it was closely followed by R 2001-2 (STI=87.92%), VG 315 (STI=84.05%), TCGS 1157 (STI=77.59%) and TG 51 (STI=73.67%). While the genotypes Girnar 3 (STI= 47.57%), OG 52-1 (STI=49.09%), TVG 0856 (STI= 49.28%) and J 86 (STI= 50.66%) were the most susceptible genotypes based on their relative performance under stress in respect of total dry weight. It has been noted further that out of the nine genotypes, KDG 197 registered the minimum reduction (4.51% over control, 2.70% over control) in total chlorophyll and sugar accumulation respectively under NaCl stress whereas, Girnar 3 recorded the highest reduction in both parameters (60.00%, 70.32% over control) respectively, under saline condition. The genotype KDG 197 and R 2001-2 accounted for the highest increase in soluble protein and proline content in their leaves (144.02%, 780.16% over control) respectively than Girnar 3. KDG 197 recorded the minimum (3.39%) increase in lipid peroxidation under stress followed by R 2001-2 with an increase of 13.04% over control plants. In contrast, Girnar 3 registered the highest increase of TBARS content and electrolyte leakage (44.44%, 31.47% over control respectively) indicating maximum membrane damage but R 2001-2 recorded the minimum (3.00%) increase in electrolyte leakage percentage than Girnar 3 (31.47% over control) followed by OG 52-1 (26.14% over control) under stress. So, better osmotic adjustment through accumulation of proline, less membrane damage the leaves helped the tolerant genotypes to sustain under salinity stress in a better way than the susceptible genotypes.

Morpho-physiological Response of Gliricidia sepium to Seawater-induced Salt Stress

Soil degradation due to the contamination of excessive saline water has been threatening soil health vis a vis plant productivity worldwide. Gliricidia sepium, a fertilizer tree, has come into limelight in recent decades in Bangladesh due to its potency in improving soil fertility. However, study on its suitability in coastal areas alongside identifying the salt-endurance limit is still lacking. Therefore, morpho-physiological attributes of G. sepium under seawater-induced different levels of salt stress were analyzed in a pot experiment from March to May 2018 to gain an insight into its salt-adaptive mechanisms. Results revealed that seawater-induced salinity negatively affected the growth-related attributes, such as plant height, fresh weight of shoots, dry weights of shoots and roots, and leaf area. The reduction of growth was coincided with reductions in photosynthetic pigments and relative water content. Interestingly, salt tolerance index was not decreased in parallel with increasing dosages of seawater, indicating the salt tolerance capacity of G. sepium. Furthermore, enhanced accumulation of proline increased the osmoprotective capacity of G. sepium in order to overcome the salt-induced osmotic stress. The results of the present study concluded that G. sepium might be suitable for growing in the salt prone areas ranging 20 – 40 dSm-1. The Agriculturists 2019; 17(1-2) 66-75

Effects of Salinity on Germination Behaviour of Two Paddy Landraces Grown in Chakrata, Dehradun, Uttarakhand, India

Germination ability of seeds varies significantly amongst different varieties of same crop when exposed to the stress. Paddy (Oryza sativa L.) is known to be highly sensitive to salinity during germination and young seedling stages. Present study was aimed to observe the effects of six salinity concentrations (0%, 0.1%, 0.5%, 1%, 1.5% and 2%) on the germination behaviour of two paddy landraces (Chenaphool and Gyasu), frequently grown in Chakrata area of district Dehradun, Uttarakhand. Salinity (>0.1%) was inversely related to final germination percentage, germination energy, plumule dry weight, plumule length, radical dry weight, radical length and speed of germination. Chenaphool landrace showed higher germination and growth (plumule and radical) at 0% salinity (control), while Gyasu landrace at 0.1% salinity level.Dry weight percentage reduction increased with increasing salinity level, while negative correlation was observed between salinity and salt tolerance index and seed vigour index for both the varieties. The study concluded that the long grained, irrigated landrace Chenaphool was more sensitive to salinity in comparison to short grained, non-irrigated landrace Gyassu. Lower salinity conditions have no adverse effects on the germination behaviour of Gyasu landrace.

Salt Resistance of Tomato (Lycopersicon esculentum Mill.) Cultivars Produced in Benin at Germination Stage

Aims: In this research study, salt resistance level of seven tomato cultivars grown in Benin, namely Akikon, Tounvi; F1 Mongal, Petomech, Padma, TLCV 15 and Thorgal was evaluated at the germination stage. Study Design: The experiment was laid out as a completely randomized design with four replications. Place and Duration of Study: The experiment was carried out in the Laboratory of Plant Physiology and Abiotic Stresses Study of University of Abomey-Calavi, Republic of Benin from May to June, 2017. Methodology: Seeds were submitted to treatment with four NaCl concentrations (0; 30; 60 and 90 mM NaCl) in Petri dishes. Seed germination was checked every day during ten days incubation period. Four replicates of 40 seeds each were used. Results: NaCl reduced seed germination rate in all cultivars from day 2 to day 10 and the germination index proportionately to NaCl concentration. At the end of the 10 days, salt stress reduced the final germination percentages with a significant difference among cultivars: cultivars F1 Mongal followed by Akikon, Thorgal, TLCV15 and Tounvi were less affected in comparison with the two other cultivars. Salt Tolerance Index was significantly variable according to the cultivar with the highest values for cultivars F1 Mongal (1.086), Akikon (1.028), TLCV15 (1.005) and Tounvi (0.989) and the weakest value for cultivar Petomech (0.436). Conclusion: NaCl stress delayed seed germination and reduced the rate of final germination. Salt Tolerance Index was variable among the seven cultivars. Based on this criterion, cultivars F1 Mongal, Akikon, TLCV15 and Tounvi were the most salt-resistant whereas Petomech was the most salt-sensitive at germination stage.