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.     

SHORT COMMUNICATION: Effect of Salt Stress on Peruvian Germplasm of Chenopodium quinoa Willd.: A Promising Crop

Soil salinity is a major problem in today’s agriculture. Quinoa has become an important crop because it exhibits high levels of salinity tolerance. In addition, its seeds contain an excellent balance of carbohydrates, lipids, amino acids and proteins for human nutrition. The quinoa germplasm includes almost 2500 accessions, some of which have been tested under salt stress. Here, we report the effect of NaCl on the germination of 182 previously untested accessions. When seeds were irrigated with saline water at 30 dS m^?1 EC, the stress appeared to be too high: all accessions showed less than 60 % germination. In contrast, irrigation with 25 dS m^?1 EC saline water allowed over 60 % germination in 15 accessions. These latter accessions’ agricultural traits were then evaluated. The overall coefficients of variation indicated that quinoa genotype and salt treatment dramatically influence root dry mass per plant, but do not noticeably affect the length of the plant’s life cycle. Unexpectedly, salt treatment resulted in increased plant height, leaf dry mass and grain yield. Using Euclidean distance for the simultaneous selection of these five agricultural traits, accessions 100, 136, 127 and 105 proved to be the best performing genotypes under salt stress.     

Saponin seed priming improves salt tolerance in quinoa

Quinoa (Chenopodium quinoa Willd.) is a facultative halophyte of great value, and World Health Organization has selected this crop, which may assure future food and nutritional security under changing climate scenarios. However, germination is the main critical stage of quinoa plant phenology affected by salinity. Therefore, two experiments were conducted to improve its performance under salinity by use of saponin seed priming. Seeds of cv. Titicaca were primed in seven different solutions with varying saponin concentrations (i.e. 0%, 0.5%, 2%, 5%, 10%, 15%, 25% and 35%), and then, performances of primed seeds were evaluated based on mean germination time and final germination percentage in germination assays (0 and 400 mM NaCl stress). Saponin solutions of 10%, 15% and 25% concentration were found most effective priming tools for alleviating adverse effects of salt stress during seed germination. Performances of these primed seeds were further evaluated in pot study. At six‐leaf stage, plants were irrigated with saline water having either 0 or 400 mM NaCl. The results indicated that saline irrigation significantly decreased the growth, physiology and yield of quinoa, whereas saponin priming found operative in mitigating the negative effects of salt stress. Improved growth, physiology and yield performance were linked with low ABA concentration, better plant water (osmotic and water potential) and gas relations (leaf photosynthetic rate, stomatal conductance), low Na⁺ and high K⁺ contents in leaves. Our results suggest that saponin priming could be used as an easy‐operated and cost‐effective technology for sustaining quinoa crop growth on salt‐affected soils.     

Paclobutrazol improves salt tolerance in quinoa: Beyond the stomatal and biochemical interventions

Quinoa is gaining importance on global scale due to its excellent nutritious profile and environmental stress‐enduring potential. Its production decreases under high salt stress but can be improved with paclobutrazol application. This study showed involvement of some potential protective mechanisms in root and leaf tissues of quinoa plants treated with paclobutrazol (PBZ) against high salinity. The treatment levels were based on preliminary experiments, and it was found that salt stress (400 mm NaCl) markedly reduced growth and photosynthetic pigments while PBZ (20 mg/L) application significantly improved these attributes. Stomata density and aperture declined on adaxial and abaxial surfaces of leaves due to salinity. Paclobutrazol application significantly improved the stomatal density on both surfaces of leaves. Concentration of proline and soluble sugars increased in root and leaf tissues under salinity, which was more obvious in PBZ‐treated plants. Salinity stress induced the oxidative damage by increasing lipid peroxidation (MDA) level in roots and more specifically in leaf tissues. However, PBZ treatments ameliorated the drastic effects of salinity and markedly reduced oxidative damage in salt‐stressed quinoa plants. Enhanced activity of enzymatic antioxidants such as superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) was triggered by PBZ application, more pronounced in leaf than root tissues. Based on these findings, we conclude that PBZ application improves the salt tolerance in quinoa by activation of the above‐mentioned physiological and biochemical mechanisms specifically in leaves.     

Multi-trait stability index: A tool for simultaneous selection of soya bean genotypes in drought and saline stress

Drought and salinity are the main limiting environmental factors that restrict the establishment of soya bean plants. In order to recommend genotypes for cultivation under adverse drought and saline stress conditions, multi-environment trials (MET) are needed. However, MET analysis is usually performed considering a single trait, which provides lower reliability in recommending genotypes when compared to multi-trait analysis. Thus, this study was carried out to investigate the stability of multi-trait stability index (MTSI) in 46 soya bean cultivars under the effects of drought and saline stress on seed germination and initial seedling growth. Drought and saline stresses were imposed by seed exposure to −0.20 MPa iso-osmotic solutions with polyethylene glycol—PEG 6000 (119.6 g/L) or NaCl (2.36 g/L) for 12 days at 25°C. The germination rate, seedling length and seedling dry matter were measured. We showed here how genotypic stability can be quantified by MTSI when comparing drought and salinity conditions in relation to non-stressful environment (control) and how this index can be employed under different conditions. When considering the index for multiple environments, we can select as the most stable genotypes TMG 716 RR, FPS Antares RR, AS 3610 IPRO, NS 7300 IPRO and FPS Solar IPRO among the 46 tested genotypes. Owing to high stability and gains with selection verified for these genotypes under salinity and drought conditions, they can be used as genitors in breeding programs aimed at obtaining offspring with higher resistance to antibiotic stresses.     

Genotypic Variation in Root Systems of Chickpea (Cicer arietinum L.) across Environments

Root systems of various chickpea genotypes were studied over time and in diverse environments, – varying in soil bulk density, phosphorus (P) levels and moisture regimes. In a pot study comparing a range of chickpea genotypes, ICC 4958 and ICCV 94916‐4 produced higher root length density (RLD) and root dry weight (RDW), which were better expressed under P stress conditions. In two field experiments in soils of intermediate and high soil bulk densities, ICC 4958 also had greater RLD and RDW, particularly under soil moisture stress conditions. The expression of greater rooting ability of ICC 4958 under a wide range of environmental conditions confirms its suitability as a parent for genetically enhancing drought resistance and P acquisition ability. The superiority of ICC 4958 over other genotypes was for root proliferation expressed through RLD. Thus, the variation in RLD can be the most relevant root trait that reflects chickpea's potential for soil moisture or P acquisition.     

Salinity tolerance of wild barley Hordeum vulgare ssp. spontaneum

Salinity tolerance of 47 wild barley genotypes and six barley cultivars was evaluated under control and salinity stress (300 mM NaCl) conditions. Shoot and root dry weight (DW), plant height, membrane stability index (MSI), relative water content, survival rate, leaf malondialdehyde (MDA) and proline contents, root and leaf Na, K, Ca and K/Na ratio, and chlorophyll a fluorescence were measured. Salinity stress caused significant increase in the MDA, proline content, Na and Ca concentrations of the roots and leaves, but resulted in a decrease in the other traits. H. spontaneum genotypes were considerably less affected by the salinity than the genotypes of H. vulgare. Plant survivability was negatively correlated with the Na concentration (r =−.66) but positively correlated with the leaf K/Na ratio (r = .67) and MSI (r = .68). Tolerance mechanisms such as ion exclusion (Na) were likely to be present in the wild barley causing K/Na homeostasis as well as the much lower root and shoot Na, resulting in the higher survival rate.     

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.     

Unequal salt distribution in the root zone increases growth and yield of cotton

Soil salinity is often heterogeneous, yet plant response to unequal salt distribution (USD) in the root zone is seldom studied in cotton (Gossypium hirsutum L.). Our objective was to evaluate the effects of USD on growth and yield, as well as its potential application for increasing cotton production. To achieve this objective, greenhouse and field experiments were conducted. In the first experiment, potted cotton plants were grown in a split-root system in the greenhouse. Each root half was irrigated with either the same or two concentrations of NaCl. Plant biomass, leaf chlorophyll (Chl), photosynthesis (Pn) and transpiration (Tr), Na⁺ and K⁺ accumulation, as well as biological and economic yields were determined. In the second experiment, plants were grown in furrow-beds in saline fields with those grown on flat beds as controls. Root-zone salinity, yield and yield components and earliness (the percentage of the first two harvests to total harvests) were monitored. When the entire root system was exposed to the same concentration of NaCl, shoot dry weight, leaf area, plant biomass, leaf Chl, Pn and Tr were markedly reduced relative to the NaCl-free control at 2 weeks after salinity stress (WAS). Significant reductions in biological (23.6–73.8%) and economic yields (38.1–79.7%) were noticed at harvest. However, when only half of the root system was exposed to low-salinity, the inhibition effect of salinity on growth and yield was significantly reduced. Plant biomass and seed cotton yield were increased by 13 and 23.9% with 50/150 mM/mM NaCl, 40 and 44.5% with 100/300 mM/mM NaCl, and 85.7 and 127.8% with 100/500 mM/mM NaCl relative to their respective equal salt distribution (ESD) controls (100/100, 200/200, and 300/300). Unequal salt distribution also decreased concentrations of Na⁺ and increased leaf K⁺ and Chl content, K⁺/Na⁺ ratio, Pn and Tr, compared with ESD. Furrow-bed seeding induced unequal distribution of salts in the surface soil during the field experiment. Under furrow planting, soil salinity was much higher, but soil osmotic potential was much lower on the ridged part than the furrows. Yield and earliness were increased 20.8 and 5.1% by furrow seeding relative to flat seeding. These enhancements were mainly attributed to unequal distribution of salts in the root zone. Thus, specific cultural practices that induce unequal salt distribution such as furrow-bed seeding can be used to improve cotton production in saline fields.     

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.     

Consistent Variation Across Soil Types in Salinity Resistance of a Diverse Range of Chickpea (Cicer arietinum L.) Genotypes

Chickpea is considered sensitive to salinity, but the salinity resistance of chickpea germplasm has rarely been explored. This study aimed to (i) determine whether there is consistent genetic variation for salinity resistance in the chickpea minicore and reference collections; (ii) determine whether the range of salinity resistance is similar across two of the key soil types on which chickpea is grown; (iii) assess the strength of the relationship between the yield under saline conditions and that under non‐saline conditions; and (iv) test whether salinity resistance is related to differences in seed set under saline conditions across soils and seasons. The seed yield of 265 chickpea genotypes in 2005–2006 and 294 cultivated genotypes of the reference set in 2007–2008 were measured. This included 211 accessions of the minicore collection of chickpea germplasm from the International Crops Research Institute for the Semi‐Arid Tropics (ICRISAT). The experiments were conducted in a partly controlled environment using a Vertisol soil in 2005–2006 and an Alfisol soil in 2007–2008, with or without 80 mm sodium chloride (NaCl) added prior to planting. In a separate experiment in 2006–2007, 108 genotypes (common across 2005–2006 and 2007–2008 evaluations) were grown under saline (80 mm NaCl) and non‐saline conditions in a Vertisol and an Alfisol soil. In 2005–2006 in the Vertisol and 2007–2008 in the Alfisol, salinity delayed flowering and maturity, and reduced both shoot biomass and seed yield at maturity. There was a large variation in seed yield among the genotypes in the saline pots, and a small genotype by environment interaction for grain yield in both soil types. The non‐saline control yields explained only 12–15 % of the variation of the saline yields indicating that evaluation for salinity resistance needs to be conducted under saline conditions. The reduction in yield in the saline soil compared with the non‐saline soil was more severe in the Alfisol than in the Vertisol, but rank order was similar in both soil types with a few exceptions. Yield reductions due to salinity were closely associated with fewer pods and seeds per pot (61–91 %) and to lesser extent from less plant biomass (12–27 %), but not seed size. Groups of consistently salinity resistant genotypes and the ones specifically resistant in Vertisols were identified for use as donor sources for crossing with existing chickpea cultivars.     

Heritability estimates of variation for NaCl tolerance in Sorghum bicolor (L.) Moench seedlings

Summary Data on root lengths of two-week-old seedlings of 51 Sorghum bicolor (L.) Moench accessions germinated in 50, 100, 150, 175, and 200 mM NaCl solutions were used to estimate broad sense heritabilities of variation for salinity tolerance.Estimates of broad sense heritabilities ranged from 0.38 to 0.73, the highest being in 50 mM NaCl, suggesting that there is potential for improving salinity tolerance in the species through selection and breeding.     

Variation in Salt Tolerance Among Some Wheat and Triticale Genotypes

The identification of genotypes having potential salt tolerance is an effective approach to solve the problems of saline soils.
Seed germination and seedling establishment are limiting factors in crop production. Seven wheat ( Triticum aestivum L.) and one Triticale (X Triticosecale Wittmak) genotypes were evaluated for salt tolerance at emergence and early seedling growth in solution culture with NaCl salinities up to 300 mM L⁻¹ (electrical conductivity equals 27.6 dS m⁻¹).
Seedling emergence was delayed by increasing NaCl in nutrient media. At 200 mM L⁻¹ NaCl, the emergence percentages of wheat genotypes ranged between 68.7 % and 91.3 % after 7 days and 79.3 % and 98.7 % after 15 days. While at 300 mM L⁻¹, the emergence percentages of the wheat genotypes were 0.0 % after 7 days. After 15 days the emergence percent ranged between 24 % and 72 %. The emergence percent of the Triticale line was 88.7 after 7 days and 89.3 after 15 days at 200 mM L⁻¹, while it was 25.3 % and 84 % after 7 and 15 days, at 300 mM L⁻¹, respectively. Root and shoot dry weight were greatly reduced by increasing NaCl, however, the Triticale line showed less reduction in growth compared to the wheat genotypes. K⁺, Ca²⁺ and Mg²⁺ were decreased with increasing salinity levels while Na⁺ content was decreased in the shoot tissues of wheat and Triticale genotypes.     

How does water and salt stress affect the germination and initial growth of Brazilian soya bean cultivars?

The effects of water and salt stress on rate of germination and seedling growth were investigated under laboratory conditions in 46 soya bean genotypes from Central-West region of Brazil to verify how these stresses may limit crop establishment during the initial growth stage and also to identify the most tolerant genotypes to drought and salinity. Mild water and salt stresses were imposed by seed exposure to –0.20 MPa iso-osmotic solutions with polyethylene glycol—PEG 6000 (119.57 g/L) or NaCl (2.357 g/L) for 12 days at 25°C. The germination percentage, seedling length and seedling dry matter were measured, and then, salt or drought tolerance indexes were calculated. The “NS 5909 RG,” “NS 7000 IPRO,” “NS 7338IPRO,” “FPS Solimões RR,” “NS 5151 IPRO,” “SYN 13610 IPRO,” “LG 60177 IPRO,” “NS 6909 IPRO” and “BMX Desafio RR” were identified as the most drought-tolerant genotypes, whereas under salinity conditions, the genotypes “5D 615 RR,” “BMX Desafio RR,” “5D 6215 IPRO” and “BMX Ponta IPRO” were identified as tolerant. The “BMX Desafio RR” is the genotype most adapted to both stress conditions and, therefore, should be used under conditions of water shortage and excess salt in the soil at sowing time.     

Antioxidative Response of Quinoa Exposed to Iso‐Osmotic,Ionic and Non‐Ionic Salt Stress

Antioxidants play an important role in adapting plants to abiotic stress by detoxifying reactive oxygen species (ROS). Involvement of antioxidant enzymes in abiotic stress tolerance of highly stress‐tolerant quinoa was studied in a climatic chamber at 6 mOsm (milliosmolar) ionic (300 mm NaCl) and non‐ionic (600 mm mannitol) salts combined with increasing levels of potassium K1 and K2 (6, 12 mm ), respectively. Fifteen days of salt treatment (both ionic and non‐ionic) decreased plant growth (shoot and root fresh weight), stomatal conductance and chlorophyll content index. Furthermore, both forms of salt stress increased the activities of superoxide dismutase, catalase, ascorbate peroxidase and peroxidase up to 2.33‐, 3.98‐, 4.78‐ and 5.55‐folds, respectively, compared to no salt treatment, whereas membrane stability index decreased corresponding to increase in lipid peroxidation (malondialdehyde), with salt treatments compared to non‐stressed plants. However, no significant effect of potassium and salt treatments has been noticed on the maximal photochemical efficiency of PSII. The results suggested that enhanced antioxidant enzymes activity under salt stress could be one of the factors responsible for abiotic stress tolerance in quinoa.     

Root Distribution of Drought-Resistant Peanut Genotypes in Response to Drought

The ability of a plant to modify its root distribution to exploit deeper stored soil water may be an important mechanism to avoid drought. This study aimed at assessing root distributions, variations in root length density (RLD) and percentage of root distribution, and the relevance of root traits for yield of drought‐resistant peanut genotypes under different available soil water levels. The experiment was conducted in the dry season during the years 2003/04 and 2004/05. Eleven peanut genotypes (ICGV 98300, ICGV 98303, ICGV 98305, ICGV 98308, ICGV 98324, ICGV 98330, ICGV 98348, ICGV 98353, Tainan 9, KK 60‐3 and Tifton‐8) and three soil moisture levels [field capacity (FC), 2/3 available soil water (AW) and 1/3 AW] were laid out in a split‐plot design with four replications. Roots were sampled by a core sampler at 37, 67 and 97 days after sowing (DAS). Root length was determined by a scanner and the WINRHIZO Pro 2004a software. RLD was calculated as the ratio of root length (cm) and soil volume (cm³). Graphical illustration of root distribution was constructed by merging RLD in the first and second soil layers (0–40 cm) as upper roots and pooling RLD at the third, fourth and fifth layers (40–100 cm) as lower roots. Pod yield, biomass and harvest index (HI) were recorded at harvest. A drought tolerance index (DTI) was calculated for each parameter as the ratio of the parameter under stress treatment to that under well‐watered conditions. Variations in RLD in 40 to 100 cm layer (RLD_{40 to 100 cm}) were found under well‐watered conditions, and the peanut genotypes could be readily identified as high, intermediate and low for this trait. Changes in RLD in the 40 to 100 cm soil layer were found at 2/3 AW and were more evident at 1/3 AW. ICGV 98300, ICGV 98303, ICGV 98305, ICGV 98308 and KK 60‐3 were classified as drought responsive as they increased RLD in the deeper subsoil level in response to drought. In general, RLD under drought conditions was not related to biomass production. The ability to maintain the percentage of RLD (DTI for %RLD) was related to pod yield, DTI for pod yield and DTI for HI. ICGV 98300, ICGV 98303, ICGV 98305 exhibited high DTI (RLD_{40 to 100 cm}) which may explain their high pod yield, DTI (PY) and DTI (HI). Based on these observations we classified them as drought‐avoiding genotypes.     

Some Agronomic and Physiological Aspects of Salt Tolerance in Cotton (Gossypium hirsutum L.)

Evaluation of commonly grown cotton (Gossypium hir-sutum L.) genotypes under saline environment may help to cope with the venture of the crop failure in salt-affected soils. In a pot experiment, four cotton genotypes (MNH-93, NIAB-78. S-12, and B-557) were grown to compare their relative performance on a sandy clay loam soil (original ECe = 1.9 dS m⁻¹) salinized with a salt mixture (Na₂SO₄, NaCl, CaCl₂, MgSO₄ in the ratio of 9:5:5:1 on equivalent basis) to EQ levels of 10 and 20 dS m⁻¹. The crop was raised to the flower initiation stage. The imposed salinity stress exhibited deleterious effect on the germination and vegetative growth with significant differences among the genotypes. Leaf area, stem thickness, shoot (stem + leaves) and root weights decreased with the increase in substrate salinity. NIAB-78 showed the least decline followed by MNH-93. Leaf thickness showed an opposite trend as an increase in this parameter was observed with the rising salinity, the maximum increase being in the case of NIAB-78. Analysis of the leaf sap showed increased Na⁺ and Cl⁻ concentrations and decreased K⁺ concentration with the increase in substrate salinity. A better osmotic adjustment, a lower Na⁺/K⁺ ratio and a lower Cl concentration were found in the leaves of NIAB-78 followed by MNH-93. This contributed towards their better growth performance under saline conditions.     

基于SNP遗传图谱定位盐、旱胁迫下甘蓝型油菜种子发芽率的QTL

研究盐胁迫、干旱胁迫下甘蓝型油菜的发芽率,寻找与发芽率相关联的分子标记,可为油菜逆境胁迫下种子萌发的分子标记辅助育种提供理论依据。本研究以甘蓝型黄籽油菜GH06和甘蓝型黑籽油菜P174为亲本,通过单粒传法(single seed descent, SSD)连续自交9代构建重组自交系群体。采用16 g L^–1的NaCl溶液进行盐胁迫,20% (W/W)的PEG-6000溶液模拟干旱胁迫,处理重组自交系种子并统计其发芽率。实验室构建的SNP遗传图谱,包含2795个SNP多态性标记位点,总长1832.9 cM,相邻标记间平均距离为0.66 cM,利用该图谱并采用复合区间作图法(CIM)分析两种胁迫条件下第3天、第4天及累计4 d后发芽率的QTL。共检测到19个QTL,分布于A01、A03、A06、A07、A09和C06染色体上。其中,11个盐胁迫相关的QTL可解释的变异为4.9%~10.9%,8个干旱胁迫相关的QTL可解释的变异为3.8%~6.9%;并且在A03和A09染色体上,盐胁迫和干旱胁迫下检测到的QTL有相近区段。研究结果表明油菜种子发芽率属于典型的数量性状,受环境影响较大;且随着胁迫时间的延长,油菜种子启动了不同的基因来响应环境胁迫。     

Identification and Characterization of Salt Tolerance of Wheat Germplasm Using a Multivariable Screening Approach

Salinity is one of the major limitations to wheat production worldwide. This study was designed to evaluate the level of genetic variation among 150 internationally derived wheat genotypes for salinity tolerance at germination, seedling and adult plant stages, with the aim of identifying new genetic resources with desirable adaptation characteristics for breeding programmes and further genetic studies. In all the growth stages, genotype and salt treatment effects were observed. Salt stress caused 33 %, 51 % and 82 % reductions in germination vigor, seedling shoot dry matter and seed grain yield, respectively. The rate of root and shoot water loss due to salt stress exhibited significant negative correlation with shoot K⁺, but not with shoot Na⁺ and shoot K⁺/Na⁺ ratio. The genotypes showed a wide spectrum of response to salt stress across the growth stages; however, four genotypes, Altay2000, 14IWWYTIR‐19 and UZ‐11CWA‐8 (tolerant) and Bobur (sensitive), exhibited consistent responses to salinity across the three growth stages. The tolerant genotypes possessed better ability to maintain stable osmotic potential, low Na⁺ accumulation, higher shoot K⁺ concentrations, higher rates of PSII activity, maximal photochemical efficiency and lower non‐photochemical quenching (NPQ), resulting in the significantly higher dry matter production observed under salt stress. The identified genotypes could be used as parents in breeding for new varieties with improved salt tolerance as well as in further genetic studies to uncover the genetic mechanisms governing salt stress response in wheat.