Assessment of salinity tolerance based upon seedling root growth response functions in maize (Zea mays L.)

Root growth response of 10-days-oldseedlings of 100 maize accessions at, 0 mM, 60 mM, 80 mM and 150 mM NaCl concentration was assessed in solution culture. The non-linear least square method was used to quantify the salt tolerance of maize accessions. The estimated salinity threshold, Ct, the NaCl concentration at which root growth starts to decrease, C0, and C50, the concentrations at which roots stop growing and 50% of its control value revealed considerable differences between the accessions. No general consistency for tolerance was, however, found between the estimates of Ct and C50. Different genetic systems appeared to be involved in controlling the inheritance of Ct and C50.Both Ct and C50 appeared to quantify accession tolerance, and the expression of root growth as a function of NaCl concentrations provides a useful guideline for salt tolerance. Estimates of broad sense heritability for relative root length were moderate in size (0.62 to 0.82), suggesting the scope for enhancing salt tolerance in maize through selection and breeding. This revised version was published online in August 2006 with corrections to the Cover Date.     

Maize genotypes with deep root systems tolerate salt stress better than those with shallow root systems during early growth

Maize (Zea mays L.) is susceptible to salinity but shows genotypic variation for salt tolerance. How maize genotypes with contrasting root morphological traits respond to salt stress remains unclear. This study assessed genotypic variation in salinity tolerance of 20 maize genotypes with contrasting root systems exposed to NaCl for 10 days (0, 50 mM or 100 mM NaCl, added in four increments every other day from 14 days after transplanting, DAT) in a semi-hydroponic phenotyping system in a temperature-controlled greenhouse. Considerable variation was observed for each of the 12 measured shoot and root traits among the 20 genotypes under NaCl treatments. Salt stress significantly decreased biomass production by up to 54% in shoots and 37% in roots compared with the non-saline control. The 20 genotypes were classified as salt-tolerant (8 genotypes), moderately tolerant (5) and salt-sensitive (7) genotypes based on the mean shoot dry weight ratio (the ratio of shoot dry weight at 100 mM NaCl and non-saline control) ± one standard error. The more salt-tolerant genotypes (such as Jindan52) had less reductions in growth, and lower shoot Na⁺ contents and higher shoot K⁺/Na⁺ ratios under salt stress. The declared salt tolerance was positively correlated with shoot height, shoot dry weight and primary root depth, and negatively correlated with shoot Na⁺ content at 100 mM NaCl. Primary root depth is critical for identifying salt responsiveness in maize plants and could be suggested as a selection criterion for screening salt tolerance of maize during early growth. The selected salt-tolerant genotypes have potentials for cultivation in saline soils and for developing high-yielding salt-tolerant maize hybrids in future breeding programmes.     

Detection of QTLs for salt tolerance in Asian barley (Hordeum vulgare L.) by association analysis with SNP markers

Two hundred ninety-six Asian barley (Hordeum vulgare L.) accessions were assessed to detect QTLs underlying salt tolerance by association analysis using a 384 single nucleotide polymorphism (SNP) marker system. The experiment was laid out at the seedling stage in a hydroponic solution under control and 250 mM NaCl solution with three replications of four plants each. Salt tolerance was assessed by leaf injury score (LIS) and salt tolerance indices (STIs) of the number of leaves (NL), shoot length (SL), root length (RL), shoot dry weight (SDW) and root dry weight (RDW). LIS was scored from 1 to 5 according to the severity of necrosis and chlorosis observed on leaves. There was a wide variation in salt tolerance among Asian barley accessions. LIS and STI (SDW) were the most suitable traits for screening salt tolerance. Association was estimated between markers and traits to detect QTLs for LIS and STI (SDW). Seven significant QTLs were located on chromosomes 1H (2 QTLs), 2H (2 QTLs), 3H (1 QTL), 4H (1 QTL) and 5H (1 QTL). Five QTLs were associated with LIS and 2 QTLs with STI (SDW). Two QTLs associated with LIS were newly identified on chromosomes 3H and 4H.     

The Genetic Basis of Variation for Salt Tolerance in Sorghum bicolor (L.) Moench Seedlings

The genetic basis of salt (NaCll tolerance at the seedling stage was examined in eight accessions of Sorghum bicolor (L.) Moench which differed in relative NaCl tolerance. The eight accessions were crossed in all possible combinations. The Nad tolerances of the resulting 56 F: hybrids and their eight parents were assessed after two weeks growth in solution cultures containing 0, 103, and 150mM NaCl. Indices of salt tolerance (relative tolerance) were used for analysis using the diallel method. Both additive and dominance effects appeared to be important for the expression of variation under low and high salinity levels, but the effect of genes with dominance properties was more pronounced. Estimates of narrow sense hentabilities for sail tolerance were appreciable, suggesting that rapid improvement in salinity tolerance is possible in this species using high selection pressures in the F₂ population.     

Vigour/tolerance trade‐off in cultivated sunflower (Helianthus annuus) response to salinity stress is linked to leaf elemental composition

Developing more stress‐tolerant crops will require greater knowledge of the physiological basis of stress tolerance. Here, we explore how biomass declines in response to salinity relate to leaf traits across 20 genotypes of cultivated sunflower (Helianthus annuus). Plant growth, leaf physiological traits and leaf elemental composition were assessed after 21 days of salinity treatments (0, 50, 100, 150 or 200 mM NaCl) in a greenhouse study. There was a trade‐off in performance such that vigorous genotypes, those with higher biomass at 0 mM NaCl, had both a larger absolute decrease and proportional decrease in biomass due to increased salinity. More vigorous genotypes at control were less tolerant to salinity. Contrary to expectation, genotypes with a low increase in leaf Na and decrease in K:Na were not better at maintaining biomass with increasing salinity. Rather, genotypes with a greater reduction in leaf S and K content were better at maintaining biomass at increased salinity. While we found an overall trade‐off between sunflower vigour and salt tolerance, some genotypes were more tolerant than expected. Further analysis of the traits and mechanisms underlying this trade‐off may allow us to breed these into high‐vigour genotypes in order to increase their salt tolerance.     

Salinity Effects on Growth and Ionic Relations of two Triticale Varieties Differing in Salt Tolerance

Two varieties of triticale possessing differential tolerance to salinity were grown in a glass-house in nutrient solution with or without the addition of 50, 100 and 150 mM NaCl. Plants were harvested after 20, 30, 37 and 44 days of vegetative growth. Relatively salt sensitive variety had slightly better growth in nutrient solution without salt throughout the study period but it could not survive at 150 mM NaCl treatment upto the final harvest. Better relative growth rates of the salt tolerant variety were observed at all salt levels during the four harvests. A significant negative correlation between Cl in shoot tissue water and the growth depression was observed for the salt sensitive variety. Better salt tolerance of the relatively salt tolerant variety seemed to be due to its ability to avoid salt build-up in plant body which was confirmed by short term Na and Cl uptake from labelled solution of 100 mM NaCl.     

Evidence for common genetic mechanisms controlling the tolerance of sudden salt stress in the tribe Triticeae

Previous studies in several Triticeae species have suggested that salt tolerance is a polygenic trait, but that genes on some chromosomes confer better tolerance to salt stress than others. This suggests an intriguing possibility that there may be a similar basis for salt tolerance in the species of the tribe Triticeae. In this study, chromosomal control of the tolerance to sudden salt stress, measured as the mean rate of leaf elongation in solution cultures with a single increment of 200 mM NaCl, was investigated in the genomes of cultivated barley (Hordeum vulgare L.), rye (Secale cereale L.), and Dasypyrum villosum (L.) Can-dargy by using disomic addition lines of individual pairs of chromosomes or chromosome arms of each of the three species in the ‘Chinese Spring’ wheat genetic background. It was observed that the chromosomes of homoeologous groups 3, 4, and 5 in barley, 5 and 7 in rye, and 4 and 6 in D. villosum carry loci with significant positive effects on salt tolerance. Increased doses of chromosomes of group 2, however, reduce or do not increase the tolerance to salt stress. These results are in agreement with a previous study of the tolerance of this salt stress regime in wheat and wheatgrass Lophopyrum elongatum. A ranking analysis of the chromosomal effects within each genome of the five Triticeae species investigated in this and previous studies revealed that the chromosomes of homoeologous groups 3 and 5 consistently confer large positive effects on the tolerance of sudden salt stress, while the chromosomes of homoeologous group 2 in increased dose have no or negative effects on the tolerance. This strongly suggests that species of the tribe Triticeae share some common genetic mechanisms of tolerance of sudden salt stress. The findings in this study give credence to the proposal that wild relatives can be exploited in the development of wheat cultivars with greater tolerance to salt stress.     

Genetic resources of salt tolerance in wild Hordeum species

Salt tolerance was evaluated in 340 accessions of Hordeum, consisting of 41 brittle-rachis forms of Hordeum vulgare L. subsp. vulgare (H. agriocrithon) accessions, 154 H. vulgare L. subsp. spontaneum (H. spontaneum) accessions, and 145 accessions of ten other species or subspecies of wild Hordeum. Germination was carried out at concentrations of 171, 257, and 342 mM NaCl. The levels of salt tolerance for seed germination in wild Hordeum species were generally lower than those found by Mano et al. (1996) in cultivated barley; the NaCl tolerance level of the different species were as follows: H. agriocrithon > H. spontaneum > other wild Hordeum species. In addition, leaf injury index was used to assess tolerance at the seedling stage after treatment with 500 mM NaCl solution for four weeks. The levels of salt tolerance at the seedling stage in wild Hordeum species were generally higher than those found by Mano & Takeda (1995) in cultivated barley. Most wild Hordeum species showed high NaCl tolerance at the seedling stage and are considered good sources of germplasm for salt tolerance breeding. This revised version was published online in August 2006 with corrections to the Cover Date.     

The Response of Four Sorghum Accessions/Cultivars to Salinity During Plant Development

Whole-plant-response of four sorghum accessions to increasing mM NaCl concentrations of 0, 100, and 150 was assessed at three growth stages (GS-1, GS-2, and GS-3), in a sand-culture experiment. Accession comparisons were made on the basis of absolute and relative salt tolerance values. Increasing salinity significantly reduced plant height at GS-1, whilst shoot and root dry weight were less affected. The effect of NaCl on these characters was greater at GS-2 and GS-3, and accessions differed significantly in their responses to salinity. On the basis of plant height data, Giza 114 had the highest absolute salt tolerance at all three growth stages. However based on shoot and root dry weight data, Double TX and Giza 114 were both significantly more NaCl-tolerant than INRA 133 and INRA 353 at GS-2. Based on relative salt tolerance values of shoot and root dry weight, and plant height, Double TX and Giza 114 were more affected by salinity at GS-3 than INRA 133 and INRA 353. INRA 133 and INRA 353 exhibited progressively higher tolerance at all growth stages, and produced more grains than Double TX and Giza 114 , and consequently had higher grain yield per plant. NaCl salinity had little effect on grain weight. Plant sensitivity to NaCl at three growth stages differs in the four accessions, and is genotype-specific. This suggests that there is considerable variation in salt tolerance in sorghum at the adult stage which may be exploited through selection and breeding of plants to effect further improvement in salinity tolerance in this species.     

Identification of pearl millet [Pennisetum glaucum (L.) R. Br.] lines tolerant to soil salinity

Crop tolerance to salinity is of high importance due to the extent and the constant increase in salt-affected areas in arid and semi-arid regions. Pearl millet (Pennistum glaucum), generally considered as fairly tolerant to salinity, could be an alternative crop option for salt affected areas. To explore the genotypic variability of vegetative-stage salinity tolerance, 100 pearl millet lines from ICRISAT breeding programs were first screened in a pot culture containing Alfisol with 250 mM NaCl solution as basal application. Subsequently, 31 lines including many parents of commercial hybrids, selected from the first trial were re-tested for confirmation of the initial salinity responses. Substantial variation for salinity tolerance was found on the basis of shoot biomass ratio (shoot biomass under salinity/ non-saline control) and 22 lines with a wide range of tolerance varying from highly tolerant to sensitive entries were identified. The performance of the genotypes was largely consistent across experiments. In a separate seed germination and seedling growth study, the seed germination was found to be adversely affected (more than 70% decrease) in more than half of the genotypes with 250 mM concentration of NaCl. The root growth ratio (root growth under salinity/control) as well as shoot growth ratio was measured at 6 DAS and this did not reflect the whole plant performance at 39 DAS. In general, the whole plant salinity tolerance was associated with reduced shoot N content, increased K⁺ and Na⁺ contents. The K⁺/Na⁺ and Ca⁺⁺/Na⁺ ratios were also positively related to the tolerance but not as closely as the Na⁺ content. Therefore, it is concluded that a large scope exists for improving salt tolerance in pearl millet and that shoot Na⁺ concentration could be considered as a potential non-destructive selection criterion for vegetative-stage screening. The usefulness of this criterion for salinity response with respect to grain and stover yield remains to be investigated.     

Quantitative trait loci controlling rice seed germination under salt stress

Salt tolerance of rice (Oryza sativa L.) at the seed germination stage is one of the major determinants for the stable stand establishment in salinity soil. One population of recombinant inbred lines (RILs, F_2:9), derived from a cross between a japonica rice landrace tolerant to salt stress and a sensitive indica rice variety, was used to determine the germination traits including imbibition rate and germination percentage under control (water) and salt stress (100 mM NaCl) for 10 days at 30 °C. The multiple interval mapping (MIM) were applied to conduct QTL for the traits. The results showed that seed germination was a quantitative trait controlled by several genes, and strongly affected by salt stress. A total of 16 QTLs were detected in this study, and each QTL could explain 4.6–43.7% of the total phenotypic variance. The expression of these QTLs might be developmentally regulated and growth stage-specific. In addition, only one digenic interaction was detected under salt stress, showing small effect on germination percentage with R² 2.7%. Among sixteen QTLs detected in this study, four were major QTLs with R² > 30%, and some novel alleles of salt tolerance genes in rice. The results demonstrated that the japonica rice Jiucaiqing is a good source of gene(s) for salt tolerance and the major or minor QTLs identified could be used to improve the salt tolerance by marker-assisted selection (MAS) in rice.     

Genomewide association analysis of salt tolerance in soybean [Glycine max (L.) Merr.]

Salinity is a common abiotic stress causing soybean [Glycine max (L.) Merr.] yield loss worldwide. The use of tolerant cultivars is an effective and economic approach to coping with this stress. Towards this, research is needed to identify salt‐tolerant germplasm and better understand the genetic and molecular basis of salt tolerance in soybean. The objectives of this study were to identify salt‐tolerant genotypes, to search for single‐nucleotide polymorphisms (SNPs) and QTLs associated with salt tolerance. A total of 192 diverse soybean lines and cultivars were screened for salt tolerance in the glasshouse based on visual leaf scorch scores after 15–18 days of 120 mM NaCl stress. These genotypes were further genotyped using the SoySNP50K iSelect BeadChip. Genomewide association mapping showed that 62 SNP markers representing six genomic regions on chromosomes (Chr.) 2, 3, 5, 6, 8 and 18, respectively, were significantly associated with salt tolerance (p < 0.001). A total of 52 SNP markers on Chr. 3 are mapped at or near the major salt tolerance QTL previously identified in S‐100 (Lee et al., 2014). Three SNPs on Chr. 18 map near the salt tolerance QTL previously identified in Nannong1138‐2 (Chen, Cui, Fu, Gai, & Yu, 2008). The other significant SNPs represent four putative minor QTLs for salt tolerance, newly identified in this study. The results above lay the foundation for fine mapping, cloning and molecular breeding for soybean salt tolerance.     

Mapping QTLs for salt tolerance in an introgression line population between Japonica cultivars in rice

QTL analysis of physiological traits related to salt tolerance was carried out using 117 BC₃F₅ lines derived from a cross between “Ilpumbyeo” as a recurrent parent and “Moroberekan” as a donor parent. The 117 introgression lines with the parents were evaluated for five traits; dry weight, fresh weight, leaf area, seedling height, and survival rate under control and salinity conditions (55 mM) at the seedling stage. To identify QTLs related to salt tolerance, 125 SSR markers showing polymorphisms between the parents were genotyped for the 117 BC₃F₅ lines. A total of eight QTLs were detected on chromosomes 1, 6, and 7. These include two QTLs on chromosomes 6 and 7 for reduction rate of dry weight (R² = 10.2∼13.6%), three QTLs on chromosomes 1, 6, and 7 for reduction rate of fresh weight (R² = 10.9∼13.9 %), two QTLs on chromosomes 1 and 7 for reduction rate of leaf area (R² = 12.1%), and one QTL on chromosome 7 for reduction rate of seedling height (R² = 10.5%). The Moroberekan alleles contributed the positive effect at these eight QTL loci. Although the parents, Ilpumbyeo and Moroberekan, were not salt tolerant as the salt tolerant check variety, Pokkali, some lines displayed a similar level of tolerance as Pokkali. The effect of the QTL on chromosome 7 was further confirmed by evaluating four lines containing the target QTL for fresh and dry weight, turgid weight, and relative water content (RWC). Significant differences between each line and Ilpumbyeo were detected for dry and fresh weight, and RWC values, and these results seem to indicate the beneficial effect of the Moroberekam alleles for salt tolerance. A set of introgression lines are being developed containing only few chromosomal segments from Moroberekan in the Ilpumbyeo background. These would be useful in developing salt tolerant lines in the breeding program.     

Evaluation of salt tolerance in rice genotypes by multiple agronomic parameters

The lack of an effective evaluation method for salt tolerance in the screening process is one of the reasons for limited success in conventional salt tolerance breeding. This study was designed to identify useful agronomic parameters for evaluation of salt tolerance and to evaluate genotypes by multiple agronomic parameters for salt tolerance at different growth stages. Twelve genotypes were grown in a greenhouse in sand and irrigated with nutrient solutions of control and treatments amended with NaCl and CaCl₂ (5:1 molar concentration) at 4.4 and 8.2 dS m^-1 electrical conductivity. Wide genotypic differences in relative salt tolerance based on seedling growth were identified. The duration of reproductive growth between panicle initiation and anthesis was either reduced or increased by salinity, but the response was not strictly correlated with relative salt tolerance in seed yield among genotypes. Wide genotypic differences in relative salt tolerance based on spikelet and tiller numbers were identified. Few genotypic differences were identified for fertility and kernel weight. Spikelet and tiller numbers contributed most of the variation to seed yield among parameters investigated. When genotypes were ranked for salt tolerance based on the means of multiple parameters, dramatic changes of salt tolerance at early and seed maturity stages were observed in two genotypes, GZ5291-7-1-2 and GZ178. IR63731-1-1-4-3-2 was identified with a favourable combination of salt tolerance at early seedling and seed maturity stages. Cluster group ranking of genotypes based on multiple agronomic characters can be applied in salt tolerance breeding to evaluate salt tolerance and may have great advantage over conventional methods. This revised version was published online in August 2006 with corrections to the Cover Date.     

Oxidative stress indicators as selection tools for salt tolerance

Oxidative stress indicators, malondialdehyde (MDA) accumulation and chlorophyll retention, were tested as tools for salt‐tolerance screening in Chloris gayana (Kunth), a forage grass exhibiting inter‐ and intra‐cultivar variability in the response to salt stress. Three types of experimental system were compared, salt shock, gradual salt treatment and leaf segments floated on control and saline solutions. Results followed the same trend in the three systems, but leaf segments or gradually salinized plants are the most convenient. Lower mean MDA and higher mean chlorophyll content were found under salinity in cv. ‘Katambora’, which is considered, from previous field trials, to be more salt tolerant than cv. ‘Boma’. Nevertheless, chlorophyll content did not give consistent results in other tests and it is not recommended for selection purposes. Within cv. ‘Boma’, clones rating higher in a salt tolerance evaluation under greenhouse conditions had lower MDA content under salinity and lower mean MDA ratios between salt‐treated and control samples. The survival of 80‘Boma’ plants under increasing NaCl concentration was assessed and MDA was measured in the leaves of very plant before the final NaCl level was reached, to assess whether it was predictive of survival capability. MDA values were significantly lower in the group surviving longer, thus, a selection based on low MDA values would have enriched the original population with more tolerant individuals.     

Genetic variation in salt tolerance at the seedling stage in an interspecific backcross inbred line population of cultivated tetraploid cotton

Soil salinity reduces cotton growth, yield, and fiber quality and has become a serious problem in the arid southwestern region of the Unites States. Development and planting of salt-tolerant cultivars could ameliorate the deleterious effects. The objective of this study was to assess the genetic variation of salt tolerance and identify salt tolerant genotypes in a backcross inbred line (BIL) population of 142 lines from a cross of Upland (Gossypium hirsutum) × Pima cotton (G. barbadense) at the seedling growth stage. As compared with the non-saline (control) conditions, seedlings under the salinity stress (200 mM NaCl) showed a significant reduction in all the plant growth characteristics measured, as expected. Even though the two parents did not differ in salt response as measured by percent reduction, significant genotype variations in the BIL population were detected for all traits except for leaf number. Based on percent reduction of the traits measured, several BILs were more salt tolerant than both parents. The results indicate that transgressive segregation occurred during the process of backcrossing and selfing even though both parents were not salt tolerant during seedling growth. Coefficients of correlation between all the traits were significantly positive, indicating an association between the traits measured. The estimates of broad-sense heritability were 0.69, 0.46, 0.47, 0.43, and 0.49 for plant height, fresh weight of shoot and root, and dry weight of shoot and root, respectively, indicating that salt tolerance during cotton seedling growth is moderately heritable and environmental variation plays an equally important role. The overall results demonstrate that backcrossing followed by repeated self-pollination is a successful strategy to enhance salt tolerance at the seedling stage by transferring genetic factors from Pima to Upland cotton.     

The potential of selection and breeding for improved salt tolerance in lucerne (Medicago sativa L.)

Summary Four cultivars of Medicago sativa L. were subjected to selection for improved salt tolerance using a salinized solution culture technique at 250 mM NaCl. Selections were made after two weeks growth, based upon seedling shoot length differences. High (shoot lengths 14–31 mm) and low (7–12 mm) selection lines were established. Unselected shoot lengths ranged from 0–11 mm. Selection intensities ranged from 0.17% to 0.22% for the high selection lines, and from 0.30% to 1.05% for the low selection lines.Eleven selected plants from cv. CUF 101, and 10 from Local Syria were grown on and polycrossed. A sample of progeny seed from each was grown at 8 NaCl concentrations in solution cultures. Selected line seedlings produced shoots at 225, 250, 260, and 275 mM NaCl, whereas unselected material failed to grow above 225 mM NaCl. A second cycle of selection at 280 mM NaCl with these two cultivars achieved selection intensities of 0.21% and 0.45% for high and low selection lines, respectively. Selected lines grew and produced shoots at 300 mM NaCl.Seedlings derived from 1st and 2nd selection cycles and unselected control material were grown for 6 weeks at 0, 150, 175, and 200 mM NaCl in a sand culture experiment. The high selection line produced significantly greater shoot fresh weight, dry weight, and % live shoot weight than the unselected control material. Clearly selection as practised here can isolate individual seedlings having enhanced genetically based tolerance to NaCl, which is manifest in mature plants derived from polycrossing those selected individuals.     

NaCl胁迫对海岛棉幼苗光合和荧光特性的影响

本文旨在研究盐胁迫对不同海岛棉品系幼苗生长指标、叶绿素含量、光合及叶绿素荧光参数的影响,为海岛棉耐盐材料的选育、栽培管理提供理论依据。以两份海岛棉—耐盐性强的品系越海9号和耐盐性弱的品系PS-7为材料,采用水培法,从发芽至三叶期,进行150 mM NaCl的持续胁迫,研究盐胁迫下不同海岛棉品系的生长指标、叶绿素含量、光合及荧光参数的变化。结果显示：持续NaCl胁迫降低了越海9号和PS-7的叶面积、根长、茎长、根/茎比值、叶绿素 a、叶绿素 b和叶绿素 a与b总量,提高了叶绿素a/b比值。盐胁迫促进了越海9号的净光合速率(Pn)、气孔导度(Gs)、胞间CO2浓度(Ci)、蒸腾速率(Tr)、水分利用率(WUE)、PSⅡ实际光化学量子产量(Y(Ⅱ))、光化学淬灭系数(qP)、光合电子传递相对速率(rETR)上升,PSII的最大光化学量子产量(Fv/Fm)和非光化学猝灭系数(NPQ)下降。盐胁迫导致PS-7的净光合速率(Pn)、气孔导度(Gs)、蒸腾速率(Tr)、水分利用率(WUE)、PSII的最大光化学量子产量(Fv/Fm)、PSⅡ实际光化学量子产量(Y(Ⅱ))、光化学淬灭系数(qP)和光合电子传递相对速率(rETR)降低,胞间CO2浓度(Ci)和非光化学猝灭系数(NPQ)提高。PS-7的根/茎比值大于越海9号,其余指标均小于越海9号。上述结果提示,持续盐胁迫抑制了海岛棉生长指标及叶绿素等生物量积累,对耐盐性弱的品系抑制程度大于耐盐性强的品系。非气孔限制因素是导致盐胁迫下PS-7净光合速率下降的主要原因。PSⅡ实际原初光能转化效率提高是引起盐胁迫下越海9号净光合速率上升的主要原因。生长指标、叶绿素含量、光合参数、叶绿素荧光参数可作为鉴定棉花耐盐材料的生理学指标。     

Does Salt Tolerance Vary in a Potential Oil-Seed Crop Brassica carinata at Different Growth Stages?

The salt tolerance of two salt-tolerant (C90-1191 and P5/80) and two salt-sensitive (C90-1115 and 77–321) lines of Ethiopian mustard ( Brassica carinata ) (selected on the basis of their performance in germinating ability and seedling growth in a screening experiment) was assessed at the adult stage under glasshouse conditions to evaluate the consistency of salt tolerance at different growth stages of plant life cycle. No difference in response of all four lines differing in salt tolerance was found to varying concentrations of NaCl in the growth medium, although the latter two lines were slightly better than the former two in shoot dry mass, seed yield or yield components. The relatively good growth of the lines C90-1115 and 77-321 at the adult stage can be related to their lower accumulation of Na, Cl and Ca in their leaves. K/Na ratios, Ca/Na ratios, K versus Na selectivity, and Ca versus Na selectivity did not prove to be successful criteria in discriminating the lines differing in degree of salt tolerance. In conclusion, salt tolerance in B. carinata varies with the change in stage of its life cycle. Thus selection based at one particular stage may not produce individuals tolerant at all growth stages.     

Identification of new QTL for salt tolerance from rice variety Pokkali

Salt stress is an ever-present threat to rice production worldwide. Rice salinity tolerance is complex, both genetically and physiologically. The success and effectiveness in selecting salt-tolerant rice variety require the identification of QTL for the tolerance and closely linked molecular markers. In the present study, a RIL population consisting of 148 lines, derived from a cross between IR29 (salt-sensitive) and Pokkali (salt-tolerant), was used to identify new QTL for salt tolerance and investigate the relationships between salt stress caused injury and the changes in different physiological and morphological traits at the seedling stage. 14,470 high-quality SNP markers generated by the Rice 56K SNP array were converted to 1,467 bin markers for linkage mapping. A high-density genetic linkage map covering 1,680.9 cM was constructed, with the physical to genetic distance ratio being 222 Kb/cM. In total, 23 QTL for different salt tolerance indices were identified, including the previously reported Saltol which is currently used in breeding programmes. Three QTL for salt injury score (SIS) were located on chromosomes 1, 4 and 12, all being closely related to the long-distant Na⁺ transport from roots to shoots. These QTL showed additive effects, thus can be effectively used in breeding programme to pyramid various tolerance genes.