Quantitative Trait Loci for Salinity Tolerance Identified under Drained and Waterlogged Conditions and Their Association with Flowering Time in Barley (Hordeum vulgare. L)

Introduction

Salinity is one of the major abiotic stresses affecting crop production via adverse effects of osmotic stress, specific ion toxicity, and stress-related nutritional disorders. Detrimental effects of salinity are also often exacerbated by low oxygen availability when plants are grown under waterlogged conditions. Developing salinity-tolerant varieties is critical to overcome these problems, and molecular marker assisted selection can make breeding programs more effective.

Methods

In this study, a double haploid (DH) population consisting of 175 lines, derived from a cross between a Chinese barley variety Yangsimai 1 (YSM1) and an Australian malting barley variety Gairdner, was used to construct a high density molecular map which contained more than 8,000 Diversity Arrays Technology (DArT) markers and single nucleotide polymorphism (SNP) markers. Salinity tolerance of parental and DH lines was evaluated under drained (SalinityD) and waterlogged (SalinityW) conditions at two different sowing times.

Results

Three quantitative trait loci (QTL) located on chromosome 1H, single QTL located on chromosomes 1H, 2H, 4H, 5H and 7H, were identified to be responsible for salinity tolerance under different environments. Waterlogging stress, daylight length and temperature showed significant effects on barley salinity tolerance. The QTL for salinity tolerance mapped on chromosomes 4H and 7H, QSlwd.YG.4H, QSlwd.YG.7H and QSlww.YG.7H were only identified in winter trials, while the QTL on chromosome 2H QSlsd.YG.2H and QSlsw.YG.2H were only detected in summer trials. Genes associated with flowering time were found to pose significant effects on the salinity QTL mapped on chromosomes 2H and 5H in summer trials. Given the fact that the QTL for salinity tolerance QSlsd.YG.1H and QSlww.YG.1H-1 reported here have never been considered in the literature, this warrants further investigation and evaluation for suitability to be used in breeding programs.     

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The current study attempted to obtain candidate doubled haploid (DH) wheat lines by serially combining two approaches: conventional chemical mutagenesis and anther culture. Additionally, the salt tolerance levels were examined between stress-treated (100 mM NaCl) and non-treated DH groups. For the molecular analysis, IRAP markers were used to characterize retrotransposon insertion polymorphisms induced by haploidization, chromosome doubling, and/or mutagenesis in the DH lines. Various sodium azide (NaN₃) concentrations (from 0 to 5 mM) were applied to seeds of the Pehlivan wheat cultivar to obtain an M₁ generation mutant population. Anther culture was set up from the M₁ mutant population. Green plant regeneration, the frequency of selected candidate mutants within the DH form and the levels of salt tolerance between samples were screened. A total of eight thousand anthers were cultured, and sixteen candidate salt-tolerant DH mutant lines, twenty-seven candidate DH mutant lines with different characteristics and one hundred and two candidate DH lines with morphologically normal appearances were obtained from the NaN₃-mutagenized population. The IRAP patterns were quite similar between the control DH lines, and the genetic differences between the controls and DHs originating from possible mutants showed close relatedness. According to previous studies, chemical mutagenesis and anther culture were combined for the first time to detect candidate salt tolerant genotypes at the DH stage. This approach might also be useful for determining the threshold dose and efficiency of wheat mutagens.     

Elucidation of salt-tolerance metabolic pathways in contrasting rice genotypes and their segregating progenies

Key message

Differentially expressed antioxidant enzymes, amino acids and proteins in contrasting rice genotypes, and co-location of their genes in the QTLs mapped using bi-parental population, indicated their role in salt tolerance.

Abstract

Soil salinity is a major environmental constraint limiting rice productivity. Salt-tolerant ‘CSR27’, salt-sensitive ‘MI48’and their extreme tolerant and sensitive recombinant inbred line (RIL) progenies were used for the elucidation of salt stress tolerance metabolic pathways. Salt stress-mediated biochemical and molecular changes were analyzed in the two parents along with bulked-tolerant (BT) and bulked-sensitive (BS) extreme RILs. The tolerant parent and BT RILs suffered much lower reduction in the chlorophyll as compared to their sensitive counterparts. Activities of antioxidant enzymes superoxide dismutase (SOD) and peroxidase (POD) and non-enzymatic antioxidant ascorbic acid were much higher in salt-stressed CSR27 and BT RILs than MI48 and BS RILs. Further, the tolerant lines showed significant enhancement in the levels of amino acids methionine and proline in response to salt stress in comparison to the sensitive lines. Similarly, the tolerant genotypes showed minimal reduction in cysteine content whereas sensitive genotypes showed a sharp reduction. Real time PCR analysis confirmed the induction of methionine biosynthetic pathway (MBP) enzymes cystathionine-β synthase (CbS), S-adenosyl methionine synthase (SAMS), S-adenosyl methionine decarboxylase (SAMDC) and serine hydroxymethyl transferase (SHMT) genes in tolerant lines, suggesting potential role of the MBP in conferring salt tolerance in rice variety CSR27. Proteome profiling also confirmed higher expression of SOD, POD and plastidic CbS and other proteins in the tolerant lines, whose genes were co-located in the QTL intervals for salt tolerance mapped in the RIL population. The study signifies integrated biochemical-molecular approach for identifying salt tolerance genes for genetic improvement for stress tolerant rice varieties.

     

A single segment substitution line population for identifying traits relevant to drought tolerance and avoidance

A population of chromosome segment substitution lines was developed using KDML105 as the recurrent parent and one of DH212 (IR68586-F2-CA-143) or DH103 (IR68586-F2-CA-31) as the donor parent. The donor parents are part of a doubled haploid population from a cross between CT9993, an upland japonica accession, and IR62266, a lowland indica accession. Multiple QTL that are relevant to drought avoidance, drought tolerance and yield traits under drought stress were mapped in this doubled haploid population and the segments selected for the chromosome segment substitution lines were chosen to capture these QTL. The chromosome segment substitution line population was phenotyped under irrigated and mild drought stress conditions, which identified that many yield traits under drought stress had been introduced into the chromosome segment substitution lines.     

Using QTL mapping to investigate the relationships between abiotic stress tolerance (drought and salinity) and agronomic and physiological traits

Background

Drought and salinity are two major abiotic stresses that severely limit barley production worldwide. Physiological and genetic complexity of these tolerance traits has significantly slowed the progress of developing stress-tolerant cultivars. Marker-assisted selection (MAS) may potentially overcome this problem. In the current research, seventy two double haploid (DH) lines from a cross between TX9425 (a Chinese landrace variety with superior drought and salinity tolerance) and a sensitive variety, Franklin were used to identify quantitative trait loci (QTL) for drought and salinity tolerance, based on a range of developmental and physiological traits.

Results

Two QTL for drought tolerance (leaf wilting under drought stress) and one QTL for salinity tolerance (plant survival under salt stress) were identified from this population. The QTL on 2H for drought tolerance determined 42% of phenotypic variation, based on three independent experiments. This QTL was closely linked with a gene controlling ear emergency. The QTL on 5H for drought tolerance was less affected by agronomic traits and can be effectively used in breeding programs. A candidate gene for this QTL on 5H was identified based on the draft barley genome sequence. The QTL for proline accumulation, under both drought and salinity stresses, were located on different positions to those for drought and salinity tolerance, indicating no relationship with plant tolerance to either of these stresses.

Conclusions

Using QTL mapping, the relationships between QTL for agronomic and physiological traits and plant drought and salinity tolerance were studied. A new QTL for drought tolerance which was not linked to any of the studied traits was identified. This QTL can be effectively used in breeding programs. It was also shown that proline accumulation under stresses was not necessarily linked with drought or salinity tolerance based on methods of phenotyping used in this experiment. The use of proline content in breeding programs can also be limited by the accuracy of phenotyping.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1243-8) contains supplementary material, which is available to authorized users.     

SALT TOLERANCE WITHIN A TYPHA POPULATION

Mc Millan , Calvin . (U. Texas, Austin.) Salt tolerance within a Typha population. Amer. Jour. Bot. 46(7): 521–526. Illus. 1959.—Typha in a disturbed salt flat near Lincoln, Nebraska, provided material for an examination of population dynamics. Within the population, clones of T. angustifolia L. tended to occupy the drier sites and those of T. latifolia L. occupied the sites of greater moisture probability. Clones of intermediate morphological characteristics were distributed with both T. angustifolia and T. latifolia. Rhizomes taken from the clones were grown in various NaCl solutions in the greenhouse. Results indicated greatest salt tolerance by T. angustifolia and least salt tolerance by T. latifolia. The intermediate, probably hybrid, clones were intermediate in salt tolerance. Seeds of the 3 clone-types germinated over the same range of salt concentration. The seeds of all 3 types withstood 4 months submergence in a 2% salt solution and germinated upon being returned to tap water. In the salt flat habitat, the clones of T. latifolia were not vigorous during the years 1956–1957 and many died or were reduced considerably in area of occupancy. The clones of T. angustifolia remained vigorous and flowered over the same period. The intermediate clones were vigorous and increased their coverage, primarily in areas that were occupied prior to 1956 by T. latifolia. The spatial adjustments within the population probably resulted from the selective action of increased salt concentration accompanying the drier conditions of 1956 and 1957.     

水稻亚铁胁迫诱导ADH的基因定位及其遗传分析

籼稻品种ＩＲ６４与粳稻品种Ａｚｕｃｅｎａ及其ＤＨ群体１３５个系用于进行Ｆｅ＾２＋胁迫（２５０ｍｇ／Ｌ,ｐＨ４．５）及对照实验,对处理及对照条件下的ＡＤＨ进行基因定位及遗传分析,结果表明,在Ｆｅ＾２＋胁迫条件下,ＡＤＨ酶的活性大大提高,群体在Ｆｅ＾２＋胁迫条件下,表现低值的超亲现象,分布偏向ＩＲ６４,单标记分析和最大似然区间作图结果表明,Ｆｅ＾２＋胁迫条件下,１１号染色体上紧密连锁的３个标记位点ＲＧ     

Yeast plasma membrane Ena1p ATPase alters alkali-cation homeostasis and confers increased salt tolerance in tobacco cultured cells

In plants, the plasma membrane Na(+)/H(+) antiporter is the only key enzyme that extrudes cytosolic Na(+) and contributes to salt tolerance. But in fungi, the plasma membrane Na(+)/H(+) antiporter and Na(+)-ATPase are known to be key enzymes for salt tolerance. Saccharomyces cerevisiae Ena1p ATPase encoded by the ENA1/PMR2A gene is primarily responsible for Na(+) and Li(+) efflux across the plasma membrane during salt stress and for K(+) efflux at high pH and high K(+). To test if the yeast ATPase would improve salt tolerance in plants, we expressed a triple hemagglutinin (HA)-tagged Ena1p (Ena1p-3HA) in cultured tobacco (Nicotiana tabacum L.) cv Bright Yellow 2 (BY2) cells. The Ena1p-3HA proteins were correctly localized to the plasma membrane of transgenic BY2 cells and conferred increased NaCl and LiCl tolerance to the cells. Under moderate salt stress conditions, the Ena1p-3HA-expressing BY2 clones accumulated lower levels of Na(+) and Li(+) than nonexpressing BY2 clones. Moreover, the Ena1p-3HA expressing BY2 clones accumulated lower levels of K(+) than nonexpressing cells under no-stress conditions. These results suggest that the yeast Ena1p can also function as an alkali-cation (Na(+), Li(+), and K(+)) ATPase and alter alkali-cation homeostasis in plant cells. We conclude that, even with K(+)-ATPase activity, Na(+)-ATPase activity of the yeast Ena1p confers increased salt tolerance to plant cells during salt stress.     

Mapping and confirmation of loci for salt tolerance in a novel soybean germplasm,Fiskeby III

Key message

The confirmation of a major locus associated with salt tolerance and mapping of a new locus, which could be beneficial for improving salt tolerance in soybean.

Abstract

Breeding soybean for tolerance to high salt conditions is important in some regions of the USA and world. Soybean cultivar Fiskeby III (PI 438471) in maturity group 000 has been reported to be highly tolerant to multiple abiotic stress conditions, including salinity. In this study, a mapping population of 132 F₂ families derived from a cross of cultivar Williams 82 (PI 518671, moderately salt sensitive) and Fiskeby III (salt tolerant) was analyzed to map salt tolerance genes. The evaluation for salt tolerance was performed by analyzing leaf scorch score (LSS), chlorophyll content ratio (CCR), leaf sodium content (LSC), and leaf chloride content (LCC) after treatment with 120 mM NaCl under greenhouse conditions. Genotypic data for the F₂ population were obtained using the SoySNP6K Illumina Infinium BeadChip assay. A major allele from Fiskeby III was significantly associated with LSS, CCR, LSC, and LCC on chromosome (Chr.) 03 with LOD scores of 19.1, 11.0, 7.7 and 25.6, respectively. In addition, a second locus associated with salt tolerance for LSC was detected and mapped on Chr. 13 with an LOD score of 4.6 and an R ² of 0.115. Three gene-based polymorphic molecular markers (Salt-20, Salt14056 and Salt11655) on Chr.03 showed a strong predictive association with phenotypic salt tolerance in the present mapping population. These molecular markers will be useful for marker-assisted selection to improve salt tolerance in soybean.

     

Genes mapping to boron tolerance QTL in barley identified by suppression subtractive hybridization

Boron tolerance is a quantitative trait controlled by multiple genes. Suppression subtractive hybridization was carried out on root cDNA from bulked boron tolerant and intolerant doubled haploid barley lines grown under moderate boron stress to identify genes associated with boron tolerance. One hundred and eleven clones representing known proteins were found to be up‐regulated in the tolerant bulk upon boron stress. Nine clones were genetically mapped to previously reported boron tolerance QTL. These include a clone identical to the boron transporter gene Bot1 and a clone coding for a bromo‐adjacent homology domain‐containing protein, mapping to the 6H boron tolerance locus and co‐segregating with reduced boron intake in a Clipper × Sahara‐3771 mapping population. A third clone mapping to the 2H QTL region encoding an S‐adenosylmethionine decarboxylase precursor was found to provide tolerance to high boron by heterologous expression. Yeast cells expressing Sahara SAMDC were able to grow on 15 mm boron solid media and maintained cellular boron concentrations at 13% lower than control cells expressing empty vector. The data suggest that an antioxidative response mechanism involving polyamines and the ascorbate–glutathione pathway in Sahara barley may provide an advantage in tolerating high soil concentrations of boron.