植物耐盐研究概况

盐害是影响农业生产的一个主要环境因素。随着全球环境的恶化,世界很多地区都发生了土地的盐渍化。近年来植物的耐盐研究已经成为研究的热点。本文从植物耐盐的机理、耐盐相关的基因及转基因植物几个方面进行综述,为从事耐盐研究的工作者提供一定的参考。     

植物耐盐性及其生理生化指标的研究进展

本文综述了盐渍化的现状、植物耐盐途径、作用机理和如何提高植物耐盐性与选育耐盐植物方法等方面的内容，并论述了植物耐盐的生理指标的鉴定。     

植物耐盐性：演化和盐基因组学

由于社会的发展需要使用盐地产出植物,因此植物耐盐性的研究变得日益重要。植物在长期演化中主要形成嗜盐植物和非嗜盐植物两类,在细胞乃至群体处理盐的机制方面发生了广泛和深度的遗传变异。鉴于发掘植物耐盐、使植物耐盐和改变植物盐环境的各领域都取得了重大进展,结合植物的演化扩展对植物耐盐的认识,从细胞机制、个体机制扩展到群体机制乃至多基因组参与的生态互作,进行以盐基因组学为视角的研究就显得非常重要。本文根据该领域的新近进展,对植物耐盐性进行演化和组学视角的回顾和分析,以期对今后的植物耐盐研究提供参考。     

植物耐盐性研究进展

盐胁迫损害植物质膜的正常功能,造成植物气孔关闭,光合降低,耗能增加,养分离子吸收不平衡.目前已从许多植物中分离了一些盐胁迫诱导的基因及基因上游序列,但对植物耐盐分子机理尚未完全阐明,主要有渗透调节、拒盐机理、盐的区隔化、钾离子运输调控系统、水通道蛋白和光合途径改变等几种假说,有些耐盐基因已被成功转入植物中.研究表明,添加一些外源物质能提高植物的耐盐性。     

耐盐和盐敏感棉品种对NaCl胁迫的抗氧化剂反应

尽管棉花被认为是耐盐植物．且不同的品种间已观察到耐盐性的变异，但是，棉花耐盐性的传递机制仍然没有解决．本研究的目的是探讨耐盐品种是否比盐敏感品种含有基本（或诱发产生）较高水平的抗氧化剂．在温室内，用０和１５０ｍＭＮａＣｌ处理耐盐棉花品种（Ａｃａｌａ１５１７—８８和Ａｃａｌａ１５１７—ＳＲ２）和盐敏感品种（Ｓｔｏｎｅｖｉｌｌｅ８２５和Ｄｅｌｔａｐｉｎｅ５０）的植株，测定它们生长状况和抗氧化剂容量的差异，结果表明，１５０ｍＭＮａＣｌ处理，使Ｄｅｌａｔｐｉｎｅ５０和Ｓｔｏｎｅｖｉｌｌｅ８２５品种植株的生长对比照下降４０％以上，而Ａｃａｌａ品种植株的生长仅下降不到３０％．耐盐品种Ａｃａｌａ的过氧化氨酶（１２１～２１５％）和α－维生素Ｅ（３１２～３４０％）的基本水平较高．盐处理后，耐盐品种过氧化物酶活性提高了３８～７２％，谷胱甘肽还原酶活性提高了５５～１０１％；而盐敏感品种这些酶活性则保持稳定或下降．生长在１５０ｍＭＮａＣｌ条件下，耐盐品种比盐敏感品种显示出氧化抗坏血酸和还原抗坏血的比率低，还原谷胱甘肽和氧化谷胱甘肽的比率高．在一次盐胁迫处理后，Ｄｅｌｔａｐｉｎｅ５０的脂质过氧化水平比Ａｃａｌａ１５１７—８８高５１％     

耐盐小麦主要农艺性状的表现及其与产量的关系

对８个耐盐小麦品种的重要农艺性状进行了研究，结果表明：盐胁迫下小麦产量构成因素中，单位面积穗数起着决定性的作用，其次是穗粒数，千粒重对产量的影响最小。盐胁迫下小麦能够顺利通过苗期，是小麦最基本的耐盐表现；个体分蘖力强，是提高耐盐小麦产量的基础。选育苗期耐盐力好、分蘖力强、成穗率高的多穗品种，同时兼顾大穗、多粒，可做为小麦耐盐育种的方向。     

小麦耐盐种质筛选及栽培调控技术研究进展

小麦耐盐种质筛选及配套栽培调控技术研究是小麦耐盐品种选育、盐碱地小麦减损稳产的前提。本文简介了小麦耐盐种质筛选流程、耐盐性评价指标与方法,重点总结了山东、河北、新疆和江苏4省的耐盐小麦品种(系)概况以及抗盐相关栽培调控技术研究进展,提出了研究存在筛选方法不统一、盐碱地实地筛选研究缺乏和栽培调控技术不系统等问题,建议统一室内筛选方法、利用室外盐池和盐碱地开展耐盐种质筛选及配套抗盐栽培调控技术研发,并基于多组学技术从遗传学和生理学角度系统探究小麦耐盐种质的耐盐机理以及栽培调控原理。     

玉米耐盐性研究进展

综述了玉米耐盐生理机制和耐盐育种的研究进展。     

大豆耐盐基因研究进展

大豆是世界上重要的粮食作物和经济作物,土地盐碱化造成大豆产量大幅度降低。了解大豆耐盐的遗传和分子机制有助于挖掘盐碱地大豆产量潜力。迄今为止从耐盐大豆种质中已分离筛选出一批耐盐相关基因,其它植物中分离的耐盐基因有些也已被用于大豆耐盐研究,研究这些基因一方面可以揭示大豆耐盐机理,另一方面可以提高大豆耐盐性。为此,从近几年有关大豆耐盐基因的遗传、挖掘与筛选、分子标记、基因定位与克隆、转化及表达等方面的相关研究结果对大豆盐胁迫耐受相关基因进行了综述,以期为大豆耐盐相关基因的快速准确定位及耐盐高产新种质的发掘利用提供理论依据。     

利用BSA-Seq方法鉴定向日葵耐盐候选基因

挖掘向日葵耐盐基因对作物耐盐品种选育具有重要的意义。本研究利用高耐盐自交系Y07-136R（父本）和不耐盐自交系Y05-222A（母本）及其构建的包含600个单株的F2分离群体为试验材料，挑选分离群体中耐盐和不耐盐的极端分离株系各50株单株，分别构建两个DNA池用于高通量测序以分析筛选向日葵耐盐候选基因。通过本研究共发掘到6个耐盐关键候选基因（Ha0_73Ns.730/Ha10.228/Ha12.2377/Ha2.3822/Ha8.182/Ha9.5434），功能注释分别为依赖ATP的RNA解旋酶、热休克蛋白、生长素结合蛋白、溶质运载蛋白家族成员、核糖体蛋白S21家族成员及未知功能蛋白。通过候选基因同源分析、代谢通路分析及共表达基因分析发现，这些基因参与植物逆境胁迫调控，可能具有耐盐的生物学功能。本研究结果为耐盐基因的克隆及功能解析提供了重要候选基因，同时为向日葵耐盐新品种的选育提供了重要的分子标记。     

Genotypic variation in salinity tolerance and its association with nodulation and nitrogen uptake in soybean

Saline soils hamper various physiological functions in soybean [Glycine max (L.) Merr.]. One example is the reduction in nitrogen (N) uptake capacity, a major dysfunction that limits soybean growth and yield under saline conditions. Previous studies have revealed that tolerance to salinity varies with cultivar; however, the cultivars used in these studies were selected solely based on agro-morphological traits. In this study, we examined genotypic variation in salinity tolerance among 85 soybean genotypes which were selected based on an assessment of both single nucleotide polymorphisms (SNP) markers and agro-morphological traits. Additionally, we examined whether salt tolerance is associated with nodulation and N uptake. We used a subset of the world soybean mini-core collection (80 cultivars) and an additional five cultivars/genetic lines (NILs72-T, NILs72-S, Enrei, En-b0-1, and En1282). All plants were grown in pots and treated with saline (final concentration of 150 mM NaCl) during the vegetative growth stage. To evaluate salinity tolerance, we used the ratio of saline-treated (S) to control (C) plant total dry weight [DW (S/C)]. The ratio differed markedly according to genotype. Furthermore, salinity-tolerant genotypes exhibited superior nodulation, leaf greenness, and N uptake under saline conditions. These results indicate that there is a marked genotypic variation in salinity tolerance, and that the tolerant genotypes exhibit greater nodulation and N uptake, although further studies are needed to clarify whether the superior nodulation and N uptake of salinity-tolerant genotypes are responsible for the observed tolerance.     

Variability in salt tolerance of native populations of Elymus scabrifolius (Döll) J. H. Hunz from Argentina

Elymus scabrifolius is a native C3 South American grass species. It is valued as forage species adapted to various environments in Argentina and is also a potential source of traits for wheat‐breeding programmes. Efficient utilization of native genetic resources requires extensive collection and characterization of available material. The purpose of this study was to identify and characterize variability in salt tolerance within E. scabrifolius populations in Argentina. Specimens of E. scabrifolius were collected from a wide range of soils in Argentina, and most populations were found in saline environments with high sodium levels. Intraspecific variability in salt tolerance was estimated, and its relation to the salinity level of the populations’ natural environment was assessed. A principal component analysis based on growth data distinguished lines from saline and non‐saline habitats only under salt conditions. Results suggest that selecting under stressed environments is a reasonable strategy for breeding E. scabrifolius. Lines of saline origin had higher biomass under both control and saline conditions, suggesting that higher gains from selection would be obtained if germplasm from this origin was used, and tillering may be the most useful indirect selection criterion for improving salt tolerance. The association between salt tolerance, ion content and osmotic adjustment was also assessed. Salt‐sensitive lines accumulated high sodium levels in leaves. However, osmotic adjustment did not correlate with the maintenance of leaf elongation rates under salinity in the genotypes included in this study.     

Stress-Activated Protein Kinase OsSAPK7 Regulates Salt-Stress Tolerance by Modulating Diverse Stress-Defensive Responses in Rice

Soil salinity is an environmental threat limiting rice productivity. Identification of salinity tolerance genes and exploitation of their mechanisms in plants are vital for crop breeding. In this study, the function of stress-activated protein kinase 7(OsSAPK7), a SnRK2 family member, was characterized in response to salt stress in rice. Compared with variety 9804, OsSAPK7-overexpression plants had a greater survival rate, increased chlorophyll and proline contents, and superoxide dismutase and catalase activities at the seedling stage under salt-stress conditions, as well as decreased sodium potassium ratio(Na~+/K~+) and malondialdehyde contents. After salt stress, the OsS APK7 knockout plants had lower survival rates, increased Na~+/K~+ ratios and malomdiadehyde contents, and decreased physiological parameters compared with 9804. These changes in transgenic lines suggested that OsSAPK7 increased the salt tolerance of rice by modulating ion homeostasis, redox reactions and photosynthesis. The results of RNA-Seq indicated that genes involved in redox-dependent signaling pathway, photosynthesis and zeatin synthesis pathways were significantly down-regulated in the OsSAPK7 knockout line compared with 9804 under salt-stress condition, which confirmed that OsSAPK7 positively regulated salt tolerance by modulating diverse stress-defensive responses in rice. These findings provided novel insights for the genetic improvement of rice and for understanding the regulatory mechanisms of salt-stress tolerance.     

Salt tolerance variability among stress‐selected Panicum coloratum cv. Klein plants

This work assessed intracultivar variability for salt tolerance within Panicum coloratum cv. Klein, explored some physiological parameters potentially associated with it and evaluated the contribution of cell division and expansion to the decreased leaf length observed under salinity. Individual plants that had survived severe stress environments in an established pasture were collected and clonal families were obtained by vegetative propagation. These were evaluated in a greenhouse, in pots with an inert substrate irrigated with nutrient solution containing 0, 200 or 400 mm NaCl. Salt tolerance was assessed from growth variables expressed as a percentage of non‐salinized controls. Changes induced by salinity in carbon fixation, soluble sugars and compatible solutes were also measured. The selected plants showed 33% higher salt tolerance than plants from the same cultivar obtained from seeds, and variability for salt tolerance was detected within the group, suggesting these plants could be valuable germplasm for breeding programmes for saline areas. All selected plants accumulated low leaf blade Na concentrations (< 0·1 mm  g^?1 dry weight on average), and K concentrations tended to remain high under salinity. A kinematic analysis indicated a reduction in the number of cells in the division‐only zone was the main cause of shorter leaves under stress. Although plants showed some differences in all these traits, they were not related to salt‐tolerance variability within this group of stress‐tolerant plants.     

Natural silicates mixed with organic fertilizers enhance corn adaptation to salt stress and improve physical characteristics of sandy soil

Soil salinity is one of the major environmental constraints to crop productivity worldwide. Therefore, the development of cost-effective and environment-friendly techniques allowing increased crop productivity and soil fertility under saline conditions is rather urgent today. The objective of this investigation was to study the effects of mixtures containing natural silicates (analcite, bergmeal, and potassium silicate) and organic fertilizers (sapropel, peat) in corn (Zea mays L.). We specifically evaluated tolerance of corn to salinity stress and certain characteristics of saline soil (viz., redox potential, conductivity, and phytotoxicity) using a factorial pot experiment, modeling NaCl salinity levels of 0, 50, 100, 150, and 200 mM under greenhouse conditions. Growth, water balance, photosynthesis, catalase activity, and accumulation of nonenzymatic antioxidants (flavonoids and anthocyanins) were measured and evaluated. Salinity stress reduced shoot and root biomass by 8–49%, photosynthetic pigment content in leaves by 15–30%, deteriorated water balance, and activated nonspecific adaptive reactions (i.e., accumulation of enzymatic and nonenzymatic antioxidants) in the corn seedlings. All the tested silicon-containing mixtures stimulated corn seedling resistance to salt stress and reduced soil phytotoxicity. This was reflected in the stimulation of growth of the corn seedlings (accumulation of shoot biomass, and formation and growth of lateral roots). The content of photosynthetic pigments, flavonoids, anthocyanins, catalase activity increased 1.3–2 times compared with plants that received NaCl only. The difference between treatments and control was most pronounced at moderate levels of salinity (100–150 mM). The mixture containing silicon minerals and sapropel (9:1 proportion) showed the highest protective effect against salinity stress.     

花生诱变材料及品系芽期耐盐性鉴定

将32个化学诱变处理M。材料共计8708粒花生种子,置于2．0％NaCl溶液中发芽,筛选出81粒露白种子,直接种植于山东省花生研究所莱西试验地,结果只有1粒出苗且长势良好。另对74份品系材料在1．0％NaCl浓度下进行了耐盐筛选,L19露白率最高（75％）,且长势良好。相关分析表明,花生芽期耐盐性与种子粗脂肪、粗蛋白、...     

Molecular Approaches to Improve Salt Resistance in Crops: Facts and Perspectives

SUMMARY

Because of the expansion of agriculture into marginal environments, enhancement of crop resistance to soil salinity is becoming a frequent objective for breeders. The tools offered by molecular biology to transfer a single or a few genes provide a major hope to reduce the negative impact of broad gene transfer that takes place in wide-cross hybridizations. Due to the presence of osmotic and toxic components in the growth response of plants to salt stress, any attempt to improve plant performance in saline environments should ensure the maintenance of an adequate flux of water into plant tissues, and also avoid the build up of ions into the cell compartments where they can exert toxic effects. Besides, reduction of injury effects due to salinity on plant tissues is a highly desirable objective. Transgenic plants overexpressing ion transporters able to exclude Na⁺ into vacuoles, the enzymes required for the biosynthesis of several osmocompatible, organic solutes, or the enzymes participating in detoxification pathways, have been obtained. Some of these transgenic plants display an enhanced growth relative to their wild type parents in saline environments, although the way in which this resistance is achieved remains essentially unknown. A fourth and promising way to engineer salt resistance in plants is the attempt to manipulate gene regulatory pathways. The extent to which these experiences, mainly with model plants, could be extrapolated to crop plants growing in the field is discussed. It is proposed that a combination of different molecular approaches could be helpful to achieve enhanced salt resistance in crop plants.     

Adaptive mechanisms of tall wheatgrass to salinity and alkalinity stress

Tall wheatgrass -Elymus elongatus (Host) Runemark- has long been used for forage production in temperate areas where salinity, alkalinity, waterlogging, or water scarcity hinder growth of other fodder species, and has a broad history of being included in revegetation programs of saline land and in wheat breeding programs. Despite its renown as a suitable species for unfavourable soil environments, the physiological mechanisms underlying its tolerance to abiotic stresses are scattered across the literature and this precludes answering the question that has motivated this review: how does tall wheatgrass endure inhospitable soil environments? The review starts with an outline of saline, alkaline and saline-alkaline soils, and their associated waterlogging or water scarcity events. This is followed by a delineation of the physiological mechanisms responsible for plant tolerance to such soils, with an emphasis on the mechanisms associated with tall wheatgrass. Briefly outlined, tall wheatgrass has shown evidence of possessing mechanisms to allow the continuity of water influx -where salinity or drought leads to reduced water availability-, strategies to avoid ion toxicity and to acquire essential nutrients, and ability to cope with high pH levels, waterlogging and excess reactive oxygen species produced as a consequence of stress. Seeking the answer to this inquiry, this review also contributes to the understanding of forage production and quality in these fragile soil environments.     

Progress in Plant Salinity Resistance Research: Need for an Integrative Paradigm

SUMMARY

Population pressure, shortage of good arable land and good quality waters are forcing crop production into more marginal environments facing abiotic stresses (drought and salinity) and thereby limiting the adaptation and productivity of staple food crops. The situation is assuming serious proportion, as almost half of the existing irrigation system of the world is under the influence of secondary salinity, sodicity or waterlogging. Therefore, to maintain productivity of existing arable land, the sustainability of the agricultural and irrigation systems that has been generated at a huge cost, is more important than immediate increases in yield. Much work done in the last century in several countries has increased our understanding of the genetics and physiology of salt tolerance of plants. Crop responses to salt stress are made up of a number of complex and interrelated, morphological, physiological, and biochemical processes. However, we still do not have a complete understanding of the underlying mechanisms of salt tolerance. The multigenic, quantitative nature of salt tolerance imposes several limitations on the efforts to improve salt tolerance of plants. The biological approach to tackle problems of salinity has its critics as well as advocates. Identification and development of crops and their cultivars with improved salt tolerance has been the key to improve productivity. Efforts in this direction using traditional methods of plant breeding and modern tools of biotechnology have led to the development and release of many cultivars with improved salt tolerance at the global level. Many of these superior cultivars have yet to prove their worth in actual stress situations. Integrative approaches in this direction, including the frontier areas of plant molecular biology have been discussed. In view of the enormity of the situation and immense challenges involved, efforts in this direction have to be more focused and multidisciplinary in approach. This should receive much higher priority and resources from scientists, administrators, and policy makers.