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.     

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.     

Productivity Enhancement in the Salt-Affected Lands of Joint Satiana Pilot Project Area of Pakistan

SUMMARY

Salt-affected lands are common in Pakistan and cover an area of 6.8 million ha; i.e., about one-third of the total cultivated area. Reduction in yield of different crops due to salinity and waterlogging is sometimes more than 60%, and annual losses under rice-wheat rotation have been calculated at Rs. 10 billion (US$ 166 million). Other adverse effects of salinity on the community are very large and about 16 million people are affected directly by the hazards of salinity and waterlogging. Average farmers in Satiana project area (38 villages) have 4–5 ha of land, of which approximately 55% are salt-affected. This area is equipped with a modern tile drainage system but it has not shown the expected impact on the rehabilitation of salt-affected soils. Farmers of Satiana area are poor and depend on off-farm activities for their livelihood. Nevertheless, they are keen to improve their soils. A productivity enhancement program was launched in the affected area, where saline agriculture was successfully demonstrated to restore the productivity of salt-affected lands and about 405 ha were successfully rehabilitated by planting salt-tolerant trees, forage shrubs, crops and applying gypsum to improve the soil conditions. Some relevant research studies used to develop the saline agriculture strategy have also been discussed.     

Sustainable,low‐input,warm‐season,grass–legume grassland mixtures: mission (nearly) impossible?

Grazing lands in warm‐temperate and subtropical North America have become less diverse. Pastures are typically grass monocultures, while rangelands are generally managed for the grass components. Overstocking, selective herbicides, fire exclusion and heavy rates of nitrogen fertilizer have contributed to near exclusion of native, warm‐season legumes. The simplicity of managing grass monocultures, pasture production responses to nitrogen fertilizer and profitability of grass‐only systems have limited interest in legume‐based approaches. Changing economics and ecological concerns with ecosystem accumulation of industrial inputs contribute to an increasing interest in legumes. Unlike the development of temperate pasture legumes and recent research in the tropics, legumes tolerant of both freezing temperatures and hot weather have received less attention. Poor establishment, limited persistence and potential invasiveness limit currently available introduced species. Native, herbaceous, warm‐season legume species occur throughout warm‐temperate North America, but little attention has been directed to these plants as potential forage species. Some success with a few native legume species, primarily in the genus Desmanthus, suggests potential for expanded assessment of forage value of the many species available. Current assessments of native legumes, primarily for conservation purposes, provide an opportunity to expand evaluations of these species for pasture and rangeland potential while economics of livestock production and public interest in ecosystem health are supportive. Experiences with legumes of warm‐temperate origin in North America, along with results with temperate and tropical pasture legumes globally, provide a starting point for future efforts at incorporating greater legume diversity in pastures and rangelands of subtropical and warm‐temperate regions around the world.     

Genetic Resources (Including Wild and Cultivated Solanum Species) and Progress in their Utilisation in Potato Breeding

The genetic resources available for the improvement of the cultivated potato (Solanum tuberosum) are reviewed along with progress in their utilisation. The conclusions are as follows. The wild and cultivated species of potato have been utilised in potato breeding to good effect, but only a very small sample of the available biodiversity has been exploited. New knowledge and technology will open possibilities for much greater use of these genetic resources in breeding. The strategy for utilising the cultivars native to Latin America will either be the introgression of desirable genes or the direct use of parents from improved populations, depending on how far modern S. tuberosum cultivars have genetically diverged from them and the extent to which S. tuberosum cultivars have been improved in the process. Molecular marker-assisted selection will be used for faster introgression of desirable genes from wild species, and the possibility exists of moving genes directly from wild species to cultivated potato with transgenic methods. New cultivars will continue to come from crosses between pairs of parents with complementary features but adapted to local growing conditions. However, increasingly these parents will possess desirable genes which have been introgressed from wild species and may also be from complementary groups of cultivated germplasm to exploit hybrid vigour. Successful cultivars may be genetically modified, if consumers see benefits in the use of the technology, to introduce genes not present in cultivated potatoes and their wild relatives to achieve novel biochemistry and further desirable improvements.     

The Use of Saline Water in Agriculture in the Near East and North Africa Region: Present and Future

SUMMARY

Salinity is a major problem that negatively impacts agricultural activities in many regions in the world, and especially the Near East and North Africa region. Generally, salinity problems increase with increasing salt concentration in irrigation water. Crop growth reduction due to salinity is generally related to the osmotic potential of the root-zone soil solution. This will lead to certain phenological changes and substantial reduction in productivity. Salinity also affects the soil physical properties. Sewage treated wastewater is an alternative water source for irrigation. Using such wastewater will provide a new water resource to expand agricultural activities as well as reduce the environmental pollution. Each country in the region has a unique system of rules and regulations to protect the quality of water resources. Important aspects that should be taken into account when using wastewater for irrigation are discussed, including some information on the different irrigation systems used in the region, and the factors leading to success of using saline water for economic crop production. Information on the use of saline water or marginal saline soils for wheat production and improvement of irrigation systems, including old land irrigation systems, under Egyptian conditions is also presented. The regional experiences and the future prospects of using saline water for crop production that vary greatly among countries in the Near East and North Africa region are summarized. This article also presents information on special cultivation methods, such as protected agriculture and soilless culture that can help in alleviating the salinity effects. Finally, the article includes some examples on the inherited knowledge for saline agriculture that conveys the grower's experience in the Near East and North Africa region where several living examples for unique and sustainable cultivation system are still in operation. One of the most impressive cultivation techniques for bio-saline crop management in Egypt is the Edkawy production system.     

A New Approach to Select Doubled Haploid Rice Lines under Salinity Stress Using Indirect Selection Index

This study determined the indirect selection index of doubled haploid(DH) rice using a multivariate analysis approach to select lines adaptive to salinity stress, comprising three experiments. The first experiment involved the selection of good agronomic characters in a field experiment conducted at an experimental station in Bogor, Indonesia. The second experiment involved salinity tolerance screening through hydroponic cultures using 0 and 120 mmol/L NaCl, conducted at a greenhouse in Bogor. The third experiment involved the validation of the indirect adaptability selection index(IASI) through a field experiment in Sukra(saline area). Field experiments followed a randomized complete block design(RCBD), whereas an RCBD nested factorial design was used for the greenhouse experiment. The first and second experiments used 56 DH lines and four check varieties with three replications. In the second experiment, Pokkali and IR29 varieties were also added as tolerant and sensitive checks of salinity, respectively. The third experiment used 28 selected DH lines, Inpari 29 and one sensitive DH line. The good agronomic index(GAI) was 0.465 yield + 0.433 number of productive tillers + 0.31 number of filled grains. This generated 24 DH rice lines with good agronomic traits. The salinity tolerance index(SaTI) was developed through the average of standardized salinity tolerance score and salinity selection index based on discriminant analysis. This generated 34 DH rice lines with good salinity stress tolerance. The IASI(IASI = GAI – Sa TI) selected 28 DH rice lines adaptive to salinity stress and it was considered effective by Sukra validation.     

Soil Salinity in South India: Problems and Solutions

SUMMARY

Soil salinity is assuming menacing proportions for production of agricultural and horticultural crops in South India. South India comprises of Andhra Pradesh (AP), Tamil Nadu (TN), Karnataka, Kerala, Goa, and Islands in Bay of Bengal (Andaman and Nicobar) and Arabian Sea (Lakshadweep). It comprises central uplands, Deccan plateau (Karnataka plateau and Telangana plateau of AP), Nilgiri hills of TN, South Sahiailri, Eastern hills (Eastern Ghats, TN, upland) and Coastal Plains. The rainfall ranges from 400 to 500 mm in AP, 450 to 1300 mm in Karnataka, 500 to 1215 mm in TN, 100 to 450 mm in Kerala. Climate is mainly semi-arid in nature. Red soils (Alfisols, Inceptisols, and Entisols) make up about 60–65% and are well drained, blacksoils (Vertisols and Inceptisols) comprise about 20–25% and the rest are coastal sands. Soil salinity problems are encountered in almost all the districts in Karnataka and AP. The area extends to about 0.176 million ha in AP, 0.2 million ha in Karnataka, 0.0427 million ha in TN and about 0.03 million ha in Kerala. Introduction of canal irrigation water and use of underground saline waters accelerated the appearance of salt affected soils. Soil salinity observed in South India ranges from hydrometphic saline soils in Kerala to highly saline (EC 20–30 dS m^?1) in Karnataka and AP. Saline soils were classified in to Natrargids or Solarthrids at subgroup level depending on the occurance of nitric or salic horizon within few centimetres of the surface. Soil salinity has reduced crop yields upto 50% and consequently cropping has been abandoned in many areas. Excess soluble salts can be removed through scrapping the surface salt crust or flushing and leaching or through subsurface drainage depending on the problem. Crops also vary in their ability to tolerate salinity at different stages of growth. In most crops subjected to irrigations with saline waters, germination and early seedling stages are generally the most sensitive and their tolerance increases with age. Salt tolerant varieties and nutrient management of crops in saline soils are important solutions for crop production under saline soils.     

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.     

Simulation for response of crop yield to soil moisture and salinity with artificial neural network

In saline fields, irrigation management often requires understanding crop responses to soil moisture and salt content. Developing models for evaluating the effects of soil moisture and salinity on crop yield is important to the application of irrigation practices in saline soil. Artificial neural network (ANN) and multi-linear regression (MLR) models respectively with 10 (ANN-10, MLR-10) and 6 (ANN-6, MLR-6) input variables, including soil moisture and salinity at crop different growth stages, were developed to simulate the response of sunflower yield to soil moisture and salinity. A connection weight method is used to understand crop sensitivity to soil moisture and salt stress of different growth stages. Compared with MLRs, both ANN models have higher precision with RMSEs of 1.1 and 1.6 t ha⁻¹, REs of 12.0% and 17.3%, and R² of 0.84 and 0.80, for ANN-10 and ANN-6, respectively. The sunflower sensitivity to soil salinity varied with the different soil salinity ranges. For low and medium saline soils, sunflower yield was more sensitive at crop squaring stage, but for high saline soil at seedling stage. High soil moisture content could compensate the yield decrease resulting from salt stress regardless of salt levels at the crop sowing stage. The response of sunflower yield to soil moisture at different stages in saline soils can be understood through the simulated results of ANN-6. Overall, the ANN models are useful for investigating and understanding the relationship between crop yield and soil moisture and salinity at different crop growth stages.     

Salt tolerance inSolanum kurzianum andS. tuberosum cvs Alpha and Russet Burbank

Summary The cultivated potatoSolanum tuberosum cvs Alpha and Russet Burbank and the wild speciesS. kurzianum were compared with respect to salt tolerance. Plants of the wild species were found to be more salt tolerant than those of the cultivated species since their growth was less impaired by the salinity, although they accumulated more sodium and less potassium ions in the shoot. Unlike the whole plant, callus derived from the wild plants was not more tolerant than that from the cultivated species. Differences in the responses to salinity between cultivated and wild plants, and between the whole plants and calli derived from them are discussed. Based on these differences and the similarity of the physiological responses to salt stress betweenS. kurzianum and the wild salt-tolerant relatives of tomato, the former is suggested as a potential source of genes for increasing the salt tolerance of potato.     

Impacts of dormancy‐regulating chemicals on innate and salinity‐induced dormancy of four forage grasses native to Arabian deserts

The effects of dormancy‐regulating chemicals (DRCs) on alleviating innate and salinity‐induced dormancy (SID) were assessed in seeds of four perennial forage grasses (Pennisetum divisum, Sporobolus spicatus, Coelachyrum brevifolium and Centropodia forsskalii). These grasses have the potential to be used for restoration or rehabilitation of degraded rangelands of the Arabian Gulf deserts. The four species showed various levels of innate dormancy. Germination of seeds stored for 2 months was not enhanced by any of the five studied DRCs in both C. brevifolium and P. divisum, but significantly improved by thiourea, fusicoccin and gibberellic acid (GA) in C. forsskalii and by thiourea, fusicoccin and nitrate in S. spicatus. Salinity had a significant negative effect on all the studied grasses. Sporobolus spicatus was more tolerant to salinity, compared with the other species. The effect of DRCs on alleviating SID depended on species. Whereas DRCs had little effect on alleviating SID in C. forsskalii and P. divisum, they greatly alleviated it in S. spicatus and C. brevifolium. Partial alleviation was observed by fusicoccin in C. brevifolium and by GA, kinetin and thiourea in C. forsskalii. Nitrate, fusicoccin and GA resulted in a complete alleviation in S. spicatus seeds in 200 mm NaCl.     

Salvadora persica, a potential species for industrial oil production in semiarid saline and alkali soils

Salinity and alkalinity are the two most important factors limiting agricultural productivity in arid and semiarid regions. Reclaiming these lands for commercial crops is too costly for most countries to afford. Faced with a declining base of arable farmland and increasing demand for food, fiber and energy, this warrants the need for utilization of naturally salt tolerant species (halophytes) in irrigated and non-irrigated agriculture. Salvadora persica, a facultative halophyte appears to be a potentially valuable oilseed crop for saline and alkali soils, since the seed contains 40–45% of oil rich in industrially important lauric (C₁₂) and myrestic (C₁₄) acids. Attempts were made to assess the performance of the species on saline and alkali soils. From the results it was evident that the species can be grown on both soil types, however height, spread and seed yield were significantly higher for plants grown on saline soils as compared to plants cultivated on alkali soils. No significant difference was observed in oil content between seed obtained from plants grown on saline and alkali soils. The study indicated that S. persica can be cultivated as a source of industrial oil on both saline and alkali soils for economic and ecological benefits, otherwise not suitable for conventional arable farming.     

Genetic Diversity of Wild Rice Species in Yunnan Province of China

Yunnan Province of China is one of the important centers for origin and evolution of cultivated rice worldwide.Wild rice is the ancestor of the cultivated rice.Many elite traits of wild rice have widened the genetic basis in cultivated rice.However,many populations of wild rice species have disappeared in the past few years.Therefore,the current status of wild rice resources should be updated and the genetic diversity of wild rice species should be examined for further germplasm preservation and utilization.Our investigations showed that the number of natural wild rice populations declined sharply in Yunnan Province during the past few years due to various reasons.Fortunately,one population of Oryza rufipogon,three of O.officinalis and ten of O.granulata have been newly found in different ecological sites,which were confirmed by inter-simple sequence repeat(ISSR) marker analysis in this study.ISSR analysis and investigation of some important traits of nutritional values indicated that the genetic diversity of the currently existing wild rice resources in Yunnan is still rich.The demonstration of genetic diversity of wild rice by a combined use of geographical distribution,morphological traits,nutrition contents and ISSR markers would be helpful for the conservation and exploration of these important wild rice resources.     

Evolutionary aspects of the trade-off between seed size and number in crops

Whereas the concept that availability of resources drives seed production is sound in principle, it is incomplete as there are many solutions to the allocation of resources that derive from the trade-off between number and size. This paper examines evolutionary aspects of this trade-off in annual grain crops. The analysis is centred on the working hypotheses that, for a given species and environment, allocation of resources to reproduction involves (H1) high plasticity in seed number, which allows for variable resource availability, and (H2) a relatively narrow range of seed size that results from evolutionary and agronomic selection. Comparisons between crops and fish are used to highlight common evolutionary elements in taxa where parents provide little or no care to their offspring, with the consequence that both number and early survival of offspring, hence fitness of parents, are partially related to embryo size and reserves.

The plasticity of seed number in relation to availability of resources is analysed against the established relationship between offspring number and parent growth rate during critical stages. The notion that seed size is under stabilising selection is analysed against three conditions: (1) mean seed size is conservative for a given species and environment, (2) seed size affects fitness, and (3) seed size is heritable. Databases from published papers were compiled to analyse the relative variability of seed size and number, and the heritability of seed size. Evidence for and against the link between seed size and parental fitness is revised using the Smith–Fretwell model as framework (Am. Nat., 108, 499–506).

The proposal of high plasticity of seed number and narrow variability of seed size resulting from stabilising natural selection is generally consistent with evolutionary and genetic considerations. Agronomic selection may have reinforced natural selection leading to relatively narrow seed size in species such as wheat and soybean, where cultivated types retained high plasticity for seed number. In contrast, selection for one or few inflorescences in crops like sunflower and maize may have morphologically reduced seed number plasticity and increased variability of seed size and its responsiveness to resource availability in relation to their wild ancestors.     

Management of Soil Salinity and Alkalinity Problems in India

SUMMARY

Like the problem of salt-affected soils afflicting many other countries with arid and semi-arid climates, these lands occupy about 8.6 M ha in India out of which 3.5 M ha are in canal commands, commonly referred to as man made or wet deserts. Starting from the early systematic work of Dr. Leather about a century ago, real impetus to development and application of reclamation technologies has occurred in the post independence period, especially the seventies. Salt-affected soils are grouped into saline and alkali/sodic soils on the considerations of soil management and crop responses. Out of the 3.4 M ha of alkali lands in Indo-Gangetic Plains, about 1.0 M ha has been reclaimed by the hydro-chemical technology. Application of amendments like gypsum, equivalent to 50% gypsum requirement, to the surface 15-cm soil only was enough to start cropping with rice. Light and frequent irrigation are ideal for upland crops. Application of higher doses of nitrogen in splits to compensate for volatilization losses, organic matter additions through green manure to increase reclaiming action, skipping phosphorus application in the initial years and the application of zinc to each crop were some of the emerging recommendations. Application of low-grade pyrites also gave encouraging results in calcareous soils. Feasibility of drainage has been successfully demonstrated in 1980s for the quicker rehabilitation of saline and waterlogged soils. Provision for subsurface drains at 1.5–2.0 m depth and 50–75 m spacing in alluvial soils and 12–24 m interval in vertisol was sufficient for facilitating growing crops within 2–3 years on lands lying barren for considerable period. However, technological, economic, social, and political considerations are the major bottlenecks for large-scale amelioration of saline soils, in addition to the safer disposal of drainage waters. Strategies worked out for successful crop production on saline soils after drainage include initial leaching management (minimizing water requirement for leaching by synchronizing with monsoon rains, etc.), proper selection of crops/cultivars, irrigation (method, controlled frequency for enhancing water-table contribution, canal water use during the initial stages including presowing for conjunctive use with drainage waters) and cultural practices (furrow planting, increasing seed rate and fertility management). Some of the future issues for combating salinity and also preventing further land degradations in India are also highlighted.     

Disease Tolerance in Helianthus petiolaris : A Genetic Resource for Sunflower Breeding

Abstract

Argentina is a major sunflower producer in the world, with crop acreage of 2?2.7 million ha in the last four years. Sunflower crop yield is often influenced by sanitary constraints, mainly fungal pathogens. Helianthus petiolaris is a wild species native to North America established in central Argentina displays a high tolerance to a number of fungal diseases and insects. Controlled crosses of this species with sunflower demonstrated that H. petiolaris constitutes a valuable genetic variability source for sunflower breeding to improve tolerance to rust (Puccinia helianthi), white rust (Albugo tragopogonis), verticillium wilt (Verticillium dahliae), powdery mildew (Erisiphe sp.) and the sunflower moth (Rachiplusia nu). This places H. petiolaris in an outstanding position as a genetic resource since different important traits could be transferred to the crop through interspecific hybridization.     

Effects of temperature and light on salinity tolerance during germination in two desert glycophytic grasses,Lasiurus scindicus and Panicum turgidum

The grasses Lasiurus scindicus and Panicum turgidum are among the most important forage species of the Arabian deserts. Both are ‘glycophytic’ or salt‐intolerant species, where seed germination becomes reduced by salinity effects. Here, we report experimental effects of light/darkness, temperature and NaCl salinity on seed germination and ‘recovery’ germination in these two species, after seeds had been transferred from saline solution to distilled water. Seeds were germinated in a range of salinities and incubated at a range of temperatures, in both light and darkness. Seeds of P. turgidum germinated significantly more in darkness than in light at temperatures 15–25°C, but the reverse was true at higher temperatures. Seeds of L. scindicus germinated well across a wide range of temperatures and in both light and darkness. In both species, germination decreased with the increase in salt concentration, and in P. turgidum germination was almost completely inhibited at a concentration of 200 mm . In saline solution, germination in darkness was significantly greater than in light at all the temperatures. Seeds of both species ‘recovered’ their germination capacity after transfer from saline solutions to distilled water. Germination recovery depended on both light and temperature of incubation in both species.     

Nutrient deficiency and hypoxia as constraints to Panicum coloratum growth in alkaline soils

Alkaline and saline–alkaline soils impose severe restrictions on plant growth. Panicum coloratum var. coloratum is a perennial C4 forage grass widely used in tropical and subtropical environments. Published information on its responses to alkaline soil conditions is scarce. The objectives of this study were (i) to characterize the effects of alkaline substrates on germination and initial growth in this species, (ii) to assess the influence of high pH in combination with reduced availability of either nutrients or oxygen and salinity, on plant growth and (iii) to evaluate some physiological traits potentially responsible for growth restrictions under alkaline soil conditions. Trials were conducted in a greenhouse. Germination and early plant survival were not affected by alkalinity. To isolate the effects of high pH, reduced nutrient and oxygen availability on growth, plants were grown either in neutral or alkaline soil, in hydroponics, in neutralized alkaline soil (with or without supplementary fertilization), or were flooded to induce hypoxia. Alkalinity effects on growth in hydroponics were milder than in soil. Growth in alkaline soil with nutrient supplement was still significantly lower (by 40%) than in neutral soil. Both alkalinity and hypoxia reduced growth non‐synergistically. These results show that studies of plant response to alkaline substrates carried out in aerated nutrient solutions can only partially address the complexity of this stress. Photosynthesis and PSII activity were among the physiological mechanisms negatively affected by alkalinity and may be partially responsible for the growth limitations observed in P. coloratum under alkaline conditions.     

野生大豆ZYD00006回交导入系构建

为挖掘野生大豆优异稀有基因，2006年至今以栽培大豆绥农14（轮回亲本）与野生大豆ZYD00006（供体 亲本）为双亲材料，经杂交、回交，标记辅助选择构建获得一套覆盖野生大豆全基因组的染色体片段导入系（代换 系）。该群体共 192个株系，包含野生大豆目标导入片段 237个，平均每个连锁群的导入片段个数为 11.85个；导入 片段总长度1865.17 cM，覆盖整个基因组的82.43%。其中L连锁群野生大豆基因组覆盖率最高，为100%，N连锁群 覆盖最低为 53.17%。最长导入片段 43.30 cM，最短导入片段 0.22 cM。高度一致的遗传背景对大豆重要基因及野 生大豆特有优异基因挖掘具有重要意义。同时，野生资源的引入极大丰富了栽培大豆的遗传基础，进而使得导入 系后代表型变异丰富，为大豆遗传育种提供重要的材料基础。