Salt-tolerant Varieties Research Articles

Impacts of cyclone and flood on crop and fish production in disaster prone coastal Bhola district of Bangladesh

This study assessed the impact of climate change induced disaster on crops and fisheries production at Bhola Sadar and Monpura upazila of Bhola district, Bangladesh during January to June 2018. The study was gathered primary data from primary observation (PO), questionnaire survey (QS), focus group discussion (FGD), and key informant interview (KII). Secondary data were collected from Upazila Agricultural Office and Upazila Fisheries Office of Bhola Sadar and Manpura upazila and moreover, climatic data were collected from Bangladesh Meteorological Department. Results of the study found that trend analysis indicates overall annual maximum temperature increased for Kharif-I, Kharif-II and Rabi season. Average annual minimum temperature also increased for Kharif-I season but decreased for Kharif-II and Rabi season. Study also found that for all cropping season average relative humidity was increased. Annual average rainfall exhibited decreasing trend for Kharif-I and Rabi season but increased for Kharif-II season in (1990-2019) time period. The Aus, T. Aman, Boro and Mung bean was dominant cropping pattern in Kharif-I, Kharif- II and Rabi season in Bhola district. Overall, Aus rice production in Kharif-I season increased but in 2009, 2013 production was decreased because of cyclone Aila (2009) and Cyclone Mahasen (2013). T. Aman production hampered due to Cyclone Sidr (2007) and flood (2014) in Kharif-II season. In Rabi season Boro rice production lessen because of low rainfall and salinity intrusion. Overall, Mung bean production increase but in 2008 and 2009 production become hampered due to late cultivation because of Cyclone Sidr (2007). Fish production rate increase in Bhola specially Hilsha fish because of non-climatic factor like raid in non-fishing time, banned current net but fish production in pond become diminished due to infrequent natural disaster. Practicing of salt and flood tolerant varieties, floating bed vegetable cultivation, and mixed cropping system (mainly for Rabi season), enhanced expedition activities against catching mother Ilish in prohibition period, dredging in the heart of the river which can eventually reduce vulnerabilities and increase crop and fish production in the Bhola region.
 Int. J. Agril. Res. Innov. Tech. 10(1): 40-55, June 2020

Changes in lipid composition in response to salt stress and its possible interaction with intracellular Na+-K+ ratio in sunflower (Helianthus annuus L.)

Present work attempts to correlate soil salinity, pH and electrical conductivity with Na+, K+ and Ca2+ uptake in field-grown salt-sensitive, semi-salt tolerant and salt-tolerant sunflower (Helianthus annuus L.) plants. Accompanying steep rise in soil salinity and electrical conductivity, salt sensitive sunflower plants exhibit root proliferation, reduced lateral root formation and early floral induction, reflecting plant’s ability to restructure root architecture and flowering under salt stress. Loss in storage lipids and downregulation of oleic and linoleic acid levels under salt stress are correlated with the massive accumulation of Na+ in the achenes of salt-sensitive sunflower plants. Long distance stress signaling in sunflower achenes is marked with accumulation/loss of novel fatty acids, such as hexanoic acid (6:0) and cis-vaccenic acid (18:1Δ11) in salt-sensitive plants and eicosanoic acid (20:0) in semi-salt tolerant plants, highlighting their possible roles in regulating plant growth under salt stress. Storage lipids, such as TAGs (triacylglycerols) of salt-tolerant variety show a 40 % decline in U/S ratio (ratio of unsaturated/saturated fatty acids) under salt stress. Semi-salt tolerant and salt-sensitive varieties display a 16 and 26 % decline in U/S ratio, respectively. Present findings, thus, provide new information on lipids as salt markers in oilseed plants.

Comparative Analysis of Proteins Involved in Energy Metabolism and Protein Processing in Pyropia haitanensis at Different Salinity Levels

The worsening of soil salinization has become an important factor limiting crop yield and quality. Pyropia haitanensis grows in the intertidal zone and is highly salt tolerant. The response mechanism of organisms exposed to stress is linked to energy metabolism and protein processing. However, the effect of hypersaline stress on the energy metabolism and protein synthesis of the P. haitanensis thallus has not been reported. Therefore, the objective of this study was to apply data-independent acquisition (DIA) technology to analyze the differences in the changes to the abundance of proteins related to energy metabolism and protein processing in P. haitanensis thalli exposed to salinity stress (100‰) and semilethal salinity (110‰). The examination of energy metabolism in algae under hypersaline stress revealed the decreased abundance of phosphofructokinase inhibits the glycolytic pathway. However, increases in triosephosphate isomerase levels and the enhancement of the pentose phosphate pathway minimize this inhibitory effect, while also providing substrates for the citric acid cycle as well as energy for physiological and biochemical algal reactions under hypersaline stress conditions. Regarding the protein processing related to the endoplasmic reticulum, increases in the abundance of CNX, the transporter COP II, heat shock proteins, protein disulfide isomerase, and other proteins related to endoplasmic reticulum quality control will ensure proteins are synthesized in algae under hypersaline stress. Increases in the levels of endoplasmic reticulum-associated degradation recognition protein BiP and transporter Sec61 as well as the ubiquitination degradation system-related proteins will maintain the dynamic balance between protein folding and clearance in algae. Moreover, algae are tolerant to 100‰ salinity, but 110‰ salinity is semilethal to algae. The abundances of citrate synthase, 6-phosphoglucose dehydrogenase, protein disulfide isomerase, and other related proteins increased under 100‰ salinity stress, but not under 110‰ salinity stress. Accordingly, in response to 100‰ salinity stress, P. haitanensis thalli may induce metabolic activities to satisfy the requirements of physiological and biochemical reactions. Furthermore, protein processing and synthesis may be stabilized to ensure necessary stress reactions are completed. The results of this study provide data potentially useful for investigating plant stress resistance mechanisms and for cultivating new salt-tolerant varieties.

Evaluation of Peanut Germplasm Tolerance to Salinity Stress

Salt-tolerant variety is the main technology for developing peanut in saline soils. However, peanut breeding for salt-tolerant characteristic has not been done in Indonesia. The aim of this study was to evaluate 25 peanut germplasm accessions of Indonesian Legumes and Tuber Crops Research Institute collection for their tolerance to salinity stress to provide gene resource for the peanut breeding. The accessions were grown at three salinity levels i.e: non saline, moderate (5-6 dS/m) and high (8-10 dS/m). Observations consisted of toxicity score, K and Na content in root and shoot, pod and seed yield, and stress tolerance index (STI). The result showed that all accessions were identified as sensitive to high salinity, and salinity 5-6 dS/m seem to be the highest level that can be tolerated by the accessions tested. At moderate salinity, four accessions (MLGA 0211, MLGA 0222, MLGA 0546, MLGA 0570) identified tolerant, two accessions (MLGA 0473 and MLGA 0605) were sensitive, and the other 19 accessions were moderate. The tolerance to salinity related to the ability of the accessions to inhibit Na uptake as well as Na translocation to the shoot, and hence K/Na ratio in shoot keeps at high level. The ratio of Na-root/Na-shoot is as effective indicator as K/Na ratio in the shoot, therefore it can be new selection criteria of peanut tolerance to salinity stress. The salt-tolerant accessions can be employed and integrated in the peanut breeding for salinity tolerance and support the development of food crops in suboptimal lands.

Interaction of variety and urea fertilizer and its impact on salt-tolerant Boro rice in the coastal area of Bangladesh

Salt-tolerant Boro rice response under the interaction of variety and urea fertilizer was assessed in the southern coastal region of Bangladesh for developing coastal agriculture in Bangladesh. A field experiment was carried out at the research field of Agriculture department, Noakhali Science and Technology University (NSTU), Noakhali-3814 in a Randomized Complete Block Design (RCBD) with two varieties viz. BINA dhan-8, BRRI dhan-67 and three doses of urea viz. 250 kg/ ha., 150 kg/ ha. and 120 kg/ ha. were used as treatments where each treatment was replicated three times. Data were collected on plant height (cm), tiller/hill, grain/panicle, 1000 grain weight (g), grain yield (t/ha.), straw yield (t/ha.) and harvest index (%). All the parameters were influenced significantly by the interaction of variety and different doses of urea fertilizer and better performance was obtained from the variety BINA dhan-8 and the doses of 250 kg urea/ ha. Finally, the present study suggests that for obtaining higher yield salt-tolerant BINA dhan-8 variety may be cultivated with 250 kg urea/ ha. in the southern coastal region of Bangladesh.
 Asian Australas. J. Food Saf. Secur. 2020, 4 (1), 1-7

Homology Modeling Identifies Crucial Amino-Acid Residues That Confer Higher Na+ Transport Capacity of OcHKT1;5 from Oryza coarctata Roxb.

HKT1;5 loci/alleles are important determinants of crop salinity tolerance. HKT1;5s encode plasmalemma-localized Na+ transporters, which move xylem Na+ into xylem parenchyma cells, reducing shoot Na+ accumulation. Allelic variation in rice OsHKT1;5 sequence in specific landraces (Nona Bokra OsHKT1;5-NB/Nipponbare OsHKT1;5-Ni) correlates with variation in salt tolerance. Oryza coarctata, a halophytic wild rice, grows in fluctuating salinity at the seawater-estuarine interface in Indian and Bangladeshi coastal regions. The distinct transport characteristics of the shoots and roots expressing the O. coarctata OcHKT1;5 transporter are reported vis-à-vis OsHKT1;5-Ni. Yeast sodium extrusion-deficient cells expressingOcHKT1;5 are sensitive to increasing Na+ (10-100 mM). Electrophysiological measurements in Xenopus oocytes expressing O. coarctata or rice HKT1;5 transporters indicate that OcHKT1;5, like OsHKT1;5-Ni, is a Na+-selective transporter, but displays 16-fold lower affinity for Na+ and 3.5-fold higher maximal conductance than OsHKT1;5-Ni. For Na+ concentrations >10 mM, OcHKT1;5 conductance is higher than that of OsHKT1;5-Ni, indicating the potential of OcHKT1;5 for increasing domesticated rice salt tolerance. Homology modeling/simulation suggests that four key amino-acid changes in OcHKT1;5 (in loops on the extracellular side; E239K, G207R, G214R, L363V) account for its lower affinity and higher Na+ conductance vis-à-vis OsHKT1;5-Ni. Of these, E239K in OcHKT1;5 confers lower affinity for Na+ transport, as evidenced by Na+ transport assays of reciprocal site-directed mutants for both transporters (OcHKT1;5-K239E, OsHKT1;5-Ni-E270K) in Xenopus oocytes. Both transporters have likely analogous roles in xylem sap desalinization, and differences in xylem sap Na+ concentrations in both species are attributed to differences in Na+ transport affinity/conductance between the transporters.

Dissemination of salt Tolerant wheat varieties through frontline demonstrations approach for sustainable wheat production in Pali district of Rajasthan

Front line demonstrations (FLDs) on wheat were laid down at 465 farmers’ fields to demonstrate production potential and economic benefits of improved production technologies comprising salinity tolerance varieties namely KRL 210, KRL 213, KRL 19 and KRL 1-4 in Pali district of arid zone of Rajasthan state during Rabi seasons from 2012-13 to 2017-18 in irrigated farming situation. The findings of the study revealed that the improved production technologies recorded an additional yield ranging from 7.1 to 16.0 q/ha with a mean of 11.1 q/ha. The per cent increase yield under improved production technologies ranged from 22.5 to 52.9 (KRL 210), 25.6 to 45.2 (KRL 213), 26.6 to 47.7 (KRL 19) and 33.8 to 45.5 (KRL 1-4) in respective years. The average extension gap, technology gap and technology index were 11.1q/ha, 11.3q/ha and 24.4 per cent, respectively in different salt tolerance varieties of wheat. The improved production technologies gave higher benefit cost ratio ranging from 2.0 to 3.0 with a mean of 2.4 as compared to local checks (1.8) being grown by farmers under locality. The results revealed that the maximum number of the respondents had medium level of knowledge and extent of adoption regarding recommended wheat production technology. The study reported lack of suitable salt tolerance HYV as major constraints by beneficiaries at rank first followed by low technical knowledge. Thus the productivity of wheat per unit area could be increased by adopting feasible scientific and sustainable management practices with a suitable salt tolerance variety. DOI.10.25174/2582-2675/2020/87064

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

Interactive effect of variety and potassium fertilizer on the yield of salt-tolerant Boro rice

Performance of salt-tolerant Boro rice was investigated under the interaction effect of variety and different doses of potassium fertilizer, which is a part of the research for developing agriculture in coastal areas of Bangladesh. A field experiment was conducted at the research field of Agriculture department, Noakhali Science and Technology University (NSTU), Noakhali-3814. The experiment was carried out in a Randomized Complete Block Design (RCBD) with three replications where two varieties viz. BINA dhan-8, BRRI dhan-28 and three doses of potassium viz. 120 kg/ha, 84 kg/ha and 36kg/ha were used as treatments. Plant height (cm), tillers/hill, grain/panicle, 1000 grain weight (g), grain yield (t/ha), straw yield (t/ha) and harvest index (%) were compared among varieties and treatments. Results revealed that only variety and only potassium fertilizer had non-significant influence but the interaction of variety and potassium fertilizer had a significant effect on the performance of salt-tolerant Boro rice. Therefore, the present study suggests that salt-tolerant BINA dhan-8 variety may be cultivated with 120 kg potassium/ha for obtaining higher yield in the southern coastal area of Bangladesh.
 Asian Australas. J. Biosci. Biotechnol. 2020, 5 (1), 21-26

Transcriptome profile analysis of two Vicia faba cultivars with contrasting salinity tolerance during seed germination

Faba bean (Vicia faba L.) is an important food legume crop. Salinity soils severely constrain the production of faba bean, however, the seed germination of faba bean, which is a vital plant growth stage, is sensitive to salinity. Planting improved varieties of faba bean, which exhibit salt tolerance in seed germination stage, is an optimal strategy for faba bean product. To investigate the genes dynamics during the seed germination stage under salinity, RNA-seq method was used to investigate genome-wide transcription profiles of two faba bean varieties with contrast salt-tolerance during the seed germination. A total of 4,486 differentially expressed genes (DEGs) were identified among the comparison of salt-tolerant variety Y134 and salt-sensitive variety Y078 treated with salinity or not. Of these, 1,410 candidate DEGs were identified as salt-stress response genes. Furthermore, 623 DEGs were identified as variety-specific response gene during seed germination at 16 h or 24 h with salt treatment. Based on the pathway enrichment according to the Kyoto Encyclopedia of Genes and Genomes database (KEGG), these DEGs involving in cell wall loosening (e.g., xyloglucan endotransglucosylase/hydrolase, chitinase, and expansin), hormone metabolism (e.g., LEA genes, genes associated with ABA or ethylene signal pathway), chromatin remodeling (e.g., chromatin structure proteins, LHP1), small interfering RNA pathway, etc., were significantly up-regulated in salt-tolerance variety with salt treatment, indicating that they play critical roles in regulation of seed germination. The results indicated that a clearer mechanism of gene regulation that regulates the seed germination responding to salinity in faba bean. These findings are helpful to increase the understanding of the salt tolerance mechanism of crops during seed germination, and provide valuable genetic resource for the breeding of salt-tolerant faba bean varieties in future.

Regulation of enzymatic and non-enzymatic antioxidants contributes to salt tolerance in hitherto unknown upland farmer rice varieties.

Salt tolerance potential of the three upland farmer varieties, koduvelliyan, mullankayama and marathondi was evaluated by comparing with the released salt-tolerant pokkali variety, vytilla-2. The salt tolerance exhibited by the upland varieties was identical with the salt tolerant variety. The superoxide (O2-) content in the upland varieties was lower; however, the hydrogen peroxide (H2O2) content increased with the salt concentration. The lesser malondialdehyde (MDA) content in the koduvelliyan variety was equivalent to the vytilla-2 and slight increase was observed in mullankayama and marathondi. The ascorbate (AsA) content in the upland varieties was comparable to vytilla-2 and upon exposure to increased concentration of NaCl, the AsA level reduced in all the treatments. Reduced glutathione (GSH) content was uniform in all the varieties up to a concentration of 100mM NaCl, however, in 125-150mM NaCl, mullankayama showed a pronounced increase in GSH content. Under salt stress, due to the formation of O2-, the oxidation of GSH was higher, maintaining a stable GSH/GSSG ratio. Superoxide dismutase (SOD) and catalase (CAT) activity of the upland varieties was higher than vytilla-2 up to 100mM NaCl, however, in 125-150mM NaCl the SOD activity increased slightly and the CAT activity decreased. Ascorbate peroxidase (APX) activity increased in upland varieties up to 125mM NaCl, and in 150mM NaCl, maintained a steady level in all the varieties. Glutathione reductase (GR) activity increased proportionate with NaCl concentration; with highest activity in all the upland varieties. Monodehydroascorbate reductase (MDHAR) activity was uniform in all the varieties up to 100mM NaCl, however, in 125 and 150mM NaCl, vytilla-2 showed higher MDHAR activity. Dehydroascorbate reductase (DHAR) activity was lesser in upland varieties under salt stress compared to vytilla-2. The GSH/GSSG ratio decreased in marathondi and koduvelliyan varieties with the increase in NaCl concentration, however, in mullankayama and vytilla-2, the GSH/GSSG ratio was higher. The membrane stability index of all the varieties was uniform in all the concentrations of NaCl used, except marathondi. The Na+ content in all the varieties increased in relation to NaCl concentration and the K+ efflux was higher suggesting a higher Na+/K+ ratio, with increased NaCl concentration.

Coupled Irrigation–Drainage Management Practice for HYV Rice Cultivation with Saline-Irrigation Water: Evidence from Lysimeter Experiment

Irrigation with saline water adversely affects rice production and degrades land productivity in the coastal zones of many countries in the world. This study aimed at developing a suitable irrigation management practice to reduce the harmful effects of salinity on rice production under saline water irrigation. An experiment in raise-bed lysimeters was set in a split-split-plot design with irrigation–drainage practice as the main factor, irrigation water salinity as the sub-factor and rice variety as sub-sub factor; main factor and sub-factor comprised four treatments and the sub-sub factor comprised three treatments, each with three replications. The treatments of the main factor were – T1: 2-5 cm continuous ponding, T2: continuous saturation, T3: changing irrigation water after 3 days of application by maintaining 2-5 cm ponding depth, and T4: changing irrigation water after 5 days of application by maintaining 2-5 cm ponding depth. The sub-factor comprised – SL1: fresh water as control, SL2: saline water of 6 dS m-1, SL3: saline water of 9 dS m-1, and SL4: saline water of 12 dS m-1. The sub-sub factor comprised three salt-tolerant rice varieties V1: Binadhan-8, V2: Binadhan-10, and V3: BRRI dhan-47. The irrigation–drainage practices T2 and T3 provided significantly (p£0.05) improved growth and yield attributes of the rice varieties under salinity water level SL3 and SL4 compared to T1 and T4 treatments. The treatment T3 maintained least exposure of the crop to high degree of salinity and produced satisfactory plant attributes by inhibiting the detrimental effects of salinity. Therefore, T3 is suggested for adoption in practical fields when provision for removing high saline water from the rice fields can be arranged.

Generation Mean Analysis and Molecular Markers for Salinity Tolerance during Wheat Germination and Seedling Stage

Generation mean analysis for salt tolerance in wheat was studied on P1, P2, F1, F2, BC1 and BC2 populations of three crosses. The cross-1 was between the salt tolerant Sakha-8 and sensitive Sham-8, cross-2 was between two salt tolerant varieties (Sakha-8 x Line-6) while cross-3 was between salt tolerant Line-6 and sensitive Sham-8. The genotypes were evaluated under control (0.0 mM NaCl) and salinity stress (150.0 mM NaCl) at germination and seedling stage for seven traits. The model of additive/dominance is inadequate for explaining the inheritance of all traits in control and salinity treatments in three crosses. The presence of epistasis in addition to the predominance of non-additive gene effects for all traits except SL indicated that the conventional selection procedure may not be effective enough to improve them. Therefore postponement of plant selection in later generations or the crosses between the selected segregants followed by selfing can be suggested to accumulate alleles favorable for the improvement of these traits. The molecular markers analysis revealed that only four SRAP primer combinations, three TRAP primer combinations and three SSR primer pairs generated polymorphic bands form the tested genotypes. The five polymorphic bands SRAP-2570bp, SRAP-3760bp, TRAP-1205bp, TRAP-3450bp and SSR-2215bp appeared only in the tolerant genotypes. These markers may be considered as specific markers for salt tolerance. The identified markers in this study would allow implementation of marker-assisted selection to screen wheat segregating populations for salt tolerance.

Salt-tolerant rice variety adoption in the Mekong River Delta: Farmer adaptationto sea-level rise.

Rice production in the Mekong River Delta of Vietnam (MRD) is endangered by sea-level rise and an associated increase in the incidence of salinity intrusion. This paper examines the diffusion of salt tolerant rice varieties in the MRD that were promoted through Consortium for Unfavorable Rice Environments (CURE) activities. Factors associated with adoption of CURE-related varieties are estimated using a random utilty model and a dataset of 800 farm households with rice fields in salinity prone areas of the MRD. Results suggest that there has been widespread adoption of CURE-related varieties in salinity-prone areas. Further, multivariate analysis reveals that environment and location characteristics, rather than household characteristics, are the most important determinants of adoption. In particular, CURE-related varieties are more likely to be adopted in high-salinity-risk areas that are not protected by salinity barrier gates. Neighbhors’ adoption decisions also strongly influence household decisions to adopt CURE-related varieties. The contracting of mechanization, particularly for land preparation and harvest, requires the coordination of village households in timing of planting, harvest and varietal duration. This coordination appears to extend to choice of CURE-related varieties. Finally, CURE-related varieties and other varieties generate similar net revenues in a year with low salinity exposure, suggesting that CURE-related varieties are a low-cost insurance policy against salinity inundation in high risk areas. Combined, these results highlight the need to address complex factors beyond current economic profits, like environment, community choices, and risk mitigation, when designing technologies and policies that support farmer adaptation to climatic change.

Salt-tolerant and -sensitive seedlings exhibit noteworthy differences in lipolytic events in response to salt stress

ABSTRACTPresent findings hypothesize that salt-tolerant and -sensitive oilseed plants are expected to exhibit deviant patterns of growth through lipolytic events in seedling cotyledons. It reports the growth response and different lipolytic mechanisms operating during oil body (OB) mobilization in the seedling cotyledons of salt-tolerant (DRSH 1) and salt-sensitive (PSH 1962) varieties of sunflower (Helianthus annuus L.). Salt tolerance or sensitivity to 120 mM NaCl correlates with high proteolytic degradation of OB membrane proteins, particularly oleosins, whereas salt-sensitive seedling cotyledons exhibit negligible proteolytic activity, thereby retaining OB membrane integrity for a longer time. High lipoxygenase (LOX) activity and its further upregulation by salt stress are the unique features of salt-sensitive sunflower seedlings. Salt-tolerant seedling cotyledons exhibit noteworthy modulation of phospholipase-D (PLD) activity by salt stress. Salt-sensitive seedling cotyledons exhibit higher lipase activity than salt-sensitive ones and enzyme activity is downregulated by salt stress. Salt-sensitive variety exhibits higher lipid accumulation and faster lipid mobilization with seedling development than salt-tolerant variety. Accumulation of oleic and linoleic acid in the seedling cotyledons of salt-tolerant and sensitive varieties exhibits differential sensitivity to salt stress. Novel detection of hexanoic acid (6:0) is a noteworthy feature as a response to salt stress in salt-sensitive variety. These findings, thus, provide new information on long-distance salt stress sensing mechanisms at seedling stage of plant development.

Comparisons of Chlorophyll Fluorescence and Physiological Characteristics of Wheat Seedlings Influenced by Iso-Osmotic Stresses from Polyethylene Glycol and Sodium Chloride

Wheat (Triticum aestivum) cultivar Taichung SEL.2 (TCS2) is a salt-tolerance variety, but the mechanism involved remains unclear. This study aims to distinguish between the non-ionic osmotic and salt-mediated physiological effects on TCS2. Osmotic agents polyethylene glycol (PEG) and sodium chloride (NaCl) were applied at three iso-osmotic levels, level 1 containing 24% (w/v) PEG and 200 mM NaCl, level 2 containing 26.5% (w/v) PEG and 250 mM NaCl), and level 3 containing 29% (w/v) PEG and 300 mM NaCl, respectively. According to the investigation of chlorophyll fluorescence in the better NaCl-treated seedlings, maximal quantum yield of photosystem II (PSII) (Fv/Fm) and significant higher effective quantum yield of PSII (ΦPSII) at level 3 were observed. Meanwhile, the non-photochemical quenching of PSII (NPQ) and the quantum yield of regulated energy dissipation of PSII [Y(NPQ)] were significantly higher in the NaCl-treated seedlings, and the quantum yield of non-regulated energy dissipation of PSII [Y(NO)] in the NaCl-treated seedlings was lower than the PEG-treated ones at level 2 and level 3. Furthermore, the less extensive degradation of photosynthetic pigments, the better ascorbate peroxidase (APX) activity and the less accumulation of malondialdehyde (MDA) were also observed in NaCl-treated seedlings. In the morphological traits, shoot elongation in NaCl-treated seedlings was also preserved. These results suggest that TCS2 is more resistant to NaCl-induced osmotic stress than to the PEG-induced stress. This study contributes to plant breeder interest in drought- and/or salt-tolerant wheat varieties.

SALT TOLERANCE OF RICE CULTIVARS IN GREENHOUSE

Abstract: The response of 10 rice cultivars, including the salt-tolerant variety (Pokkali) and salt-susceptible variety (IR29) as controls at five salinity levels (i.e., 0, 4, 6, 8, and 10 dS·m–1) under hydroponic conditions was studied at the seedling stage in the greenhouse. The heading stage was evaluated at the salinity level of 8 dS·m–1 in a completely randomized block with 3 replications per each cultivar under non-saline and saline conditions. The results show that the growth of cultivars is retarded severely at the external salinity levels. Almost all leaves dried and died completely (score 7 and 9) at the level of 8 to 10 dS·m–1. Cultivars IR29 and OM7347 died (score 9) at 10 dS·m–1; whereas, Pokkali and IR93350 were evaluated at score 5. Salinity induces the reduction of overall agronomic parameters of cultivars, especially in dry weight relative-to-reduction over control (ROC%), salt tolerance index (STI%), pollen germination, and grain yield. Salinity-sensitive cultivars decreased their pollen viability by more than 50%, leading to a poor grain yield at a salt level of 8 dS·m–1. Tested cultivars as an initial response to salinity stress were ranked as follows: OM7347, IR87832-303-1-B, and IR29 – susceptible; OM8104, IR93340, and IR93343 – moderately tolerant, and IR86385-8D-1-2-B, IR5040, IR93350, and Pokkali – tolerant.Keywords: heading stage, pollen germination, susceptible, seedling stage, salinity-tolerant

Seed priming alleviates crop growth inhibition by salinity

Salinity has become one main obstacle in increasing marginal land crop productivity. Several attempts have been made to deal with salinity. This study aimed to alleviate rice and soybean growth inhibition as caused by salinity, using seed priming during pre-sowing. The factorial Randomized Completely Block Design was used in both experiments. First experiment examined the effects of seed priming using four levels of NaCl concentrations, i.e. 0.2, 150, 300 and 450 mM NaCl on the growth and yield of two rice varieties (Dendang and IR 64) in salinity. Whereas in the second experiment, the effects of seed priming using three levels NaCl concentrations, i.e. 0, 40 and 80 mM were tested on three soybean varieties (Anjasmoro, Dering and Grobogan) under salinity. The results of first experiment showed that the two rice varieties responded differently to seed priming treatments. Seed priming using 150 mM NaCl increased leaf and root surface area as well as yield in IR 64 variety. However, Dendang (the salt tolerant variety) was less responsive to seed priming compared to IR 64. Similar results were also found from the second experiment. Among three soybean cultivars, only Dering (the salt sensitive variety) which showed a positive responses to seed priming up to 80 mM NaCl.

Evaluation and QTL Mapping of Salt Tolerance in Yardlong Bean [Vigna unguiculata (L.) Walp. Subsp. unguiculata Sesquipedalis Group] Seedlings

Salinity is a major abiotic stress that limits productivity in yardlong bean. Identification of the quantitative trait loci (QTL) underlying salt tolerance is a prerequisite for successful marker-assisted selection when breeding for salt-tolerance. The objective of this study was to use a set of insertions and deletions (InDels) found in salt stress-responsive genes to construct a linkage map and identify reliable markers that can guide breeding efforts for novel, high-yield, salt-tolerant varieties of yardlong bean (Vigna unguiculata). A linkage map was constructed from 103 InDel markers in an F2 population consisting of 143 plants produced by crossing yardlong bean varieties Suzi 41 (salt tolerant) and Sujiang 1419 (salt sensitive). The markers were clustered across 9 chromosomes spanning 975.7 cM in total length, with an average distance between adjacent markers of 9.5 cM. Using this linkage map, we identified six major QTLs associated with control of salt tolerance-related traits on chromosomes (Chr.) 08, 09, and 11, which explained 9.9% ~ 72.7% of the phenotypic variation. Four major QTLs showed co-location in the region between VUIn584 and VUIn724 on Chr.09, associated with the traits of salt tolerance rating (STR), leaf chlorophyll content (SPAD), aerial biomass fresh weight (AFW), and root fresh weight (RFW). These QTLs provide a valuable reference for marker-assisted breeding, QTL fine mapping, and the cloning and characterization of salt-tolerance candidate genes.

Growth of Wheat and Na+/ K+ Ratio under Neutral and Alkaline Salts Stress

Saline soils contain multiple types of soluble salts. Role of alkaline salts (AS) may be different than neutral salts (NS) for crop growth. Usually these types of salinity frequently co-exist. Neutral salts generally induce osmotic stress and ion-induced injury to growing crop plants. Behavior of AS may be different due to high pH. This study was conducted to see the response of wheat growth and Na+/ K+ ratio under AS and NS application as nutrient solution study. Germinated disinfected seeds of wheat (Cv. Pak-13) and raised in sand. Ten days seedlings were transferred to pots containing standard nutrients solution, with the application of 30 and 60 mM of NS (NaCl, Na2SO4) and AS (NaHCO3 and Na2CO3) separately in 1:1 ratio using complete randomize design in triplicates. The seedling growth period in salt solution comprised 33 days. Biomass and the selected inorganic ions were affected significantly (p< 0.01) under salt stress. The magnitude of loss of bio mass was 11 percent higher in AS than that of NS application. Phosphorus and sulphur concentration were lower 10 and 7 percent with AS than NS respectively besides high Na+/K+ ratio and pH. Further such studies on salt tolerant crop varieties can be carried out to differentiate response under different types of salts.