QTL mapping of physiological traits associated with salt tolerance in Medicago truncatula Recombinant Inbred Lines
Soumaya Arraouadi a ,⁎,Mounawer Badri b ,Chedly Abdelly b ,Thierry Huguet c ,Mohamed Elarbi Aouani d
a
Laboratory of Legumes,Centre of Biotechnology of Borj Cedria,B.P.901,2050Hammam-Lif,Tunisia
twitterb
bishopric
Laboratory of Plant Extremophyl,Centre of Biotechnology of Borj Cedria,B.P.901,2050Hammam-Lif,Tunisia c
Laboratoire de Symbio et Pathologie des Plantes,INP-ENSAT,B.P.107,31326Castanet Tolosan Cedex,France d
NEPAD/North Africa Biosciences Network,National Rearch Centre,El Buhouth St,Cairo,12311,Egypt
a b s t r a c t
a r t i c l e i n f o Article history:
Received 28May 2011
Accepted 30November 2011
Available online 8December uncatula
Recombinant Inbred Lines NaCl stress Na +K +
Quantitative traits loci
In this study,QTL mapping of physiological traits in the model Legume (Medicago truncatula )was performed using a t of RILs derived from LR5.Twelve parameters associated with Na +and K +content in leaves,stems and roots were measured.Broad-n heritability of the traits was ranged from 0.15to 0.83in control and from 0.14to 0.61in salt stress.Variation among RILs was dependent on line,treatment and line by treatment effect.We mapped 6QTLs in control,2in salt stress and 5for nsitivity index.No major QTL was identi fied indicating that tolerance to salt stress is governed by veral genes with low effects.Detected QTL for leaf,stem and root traits did not share the same map locations,suggesting that genes controlling transport of Na +and K +may be different.
The maximum of QTL was obrved on chromosome 1,no QTL was detected on chromosomes 5and 6.
©2011Elvier Inc.All rights rerved.
1.Introduction
Legumes are important economic crops that provide humans with food,livestock with feed,and industry with raw materials [1].The genus Medicago contains 83species,including alfalfa (Medicago sativa ),that are typically either tetraploid perennial or diploid annual species [2,3].Properties shared by the majority of legume species are the mutualistic interactions with nitrogen-fixing rhizobia and symbiotic mycorrhizal fungi [4,5].Conquently they do not need costly and polluting chemical nitrogen fertilizers [6].Salinity is one of major stress limiting crop production worldwide,affecting near 40%of agricultural lands located in arid and mi-arid climates [7].Indeed,salt can impo a multifaceted injury to Medicago genus plants,such as ed germination,vegetative growth,and yield.Medicago truncatula is widely ud as a model plant for legume genetics and genomics [8],by virtue of being an annual,diploid and autogamous legume with a moderate genome size (500–550Mbp).M.truncatula is found in a variety of edaphic and bioclimatic conditions in Tunisia,suggestin
g that genotypes adapted to local biotic and abiotic stress could be identi fied in natural populations and integrated into breeding programs.It is now recognized that tolerance of salinity by higher plants,in common with other environmental stress,is genetically
and physiologically complex,and that salt affects numerous plant process at all levels of organization.
At the very least,ion transport,lectivity,excretion,nutrition,and compartmentation are involved,together with growth,water u and water u ef ficiency.Salt tolerance of the crop is the final manifestation of veral components,such as Na +content,K +content,ion balance and ion compartmentation,etc.To keep the Na +level low inside a plant cell is not an easy task especially when the external Na +levels are high in saline soils.A major toxic ion from saline soil is Na +that gets into plant cells through Na +permeable transporters [9].In spite of a large inter and intraspeci fic variability of legume tolerance to salt,the species adopt generally the exclusive strategy,characteristic of nsitive plants.Legumes tend to restrict Na +transport towards shoots and,thus,maintain relatively low salt levels in their photosynthetic organs [10].Therefore,salt tolerance has often been found to be associated with lower accumulation of sodium (Na +)in the shoot [11,12]but not always [13].The inter-speci fic comparison of some Medicago species showed t
hat in M.arborea (salt nsitive species)the highest Na +concentrations were obrved in the leaf blades,whereas M.citrina (salt tolerant species)distributed the salt in the petioles [14].Numerous studies [15,16]tried to disct a complex physiological trait of salt tolerance using improved methods of identifying and measuring physiological components such as shoot sodium concen-tration,plant survival scores and plant vigor.However,the development of molecular markers has made genetic analysis possible to investigate quantitative inheritance;that it shows continuous variation and a high degree of environmental nsitivity [17].The identi fication of some of
Genomics 99(2012)118–125
Abbreviations:QTL,Quantitative traits loci;RILs,Recombinant Inbred Lines;LR5,A cross between the tolerant line Jemalong A17and susceptible line F83005.5.⁎Corresponding author.Fax:+21679325728.
E-mail address:bio. (S.
Arraouadi).0888-7543/$–e front matter ©2011Elvier Inc.All rights rerved.doi:
10.2011.11.005
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Genomics
j o u r n a l h o m e p a ge :w ww.e l s e v i e r.c o m/l o c a t e /y g e n o
the quantitative trait loci(QTLs)that contribute to natural variation in salt tolerance should be instrumental in eventually manipulating the perception of salinity and the corresponding respons.Therefore, Na+and K+uptake,balance and distribution within the cell and the plant have been considered of great interest for quantitative trait loci (QTL)analysis in other crops such as citrus[18],rice[19]and durum wheat[20].It is quite possible that the QTL for Na+:K+ratio,which was independent of the QTL for sodium or potassium uptake per , reflects lectivity by membrane-bas
ed transport systems.
Actually,bad on the QTL mapping in multiple related populations derived from two parents,a maximum likelihood estimation method was propod,which can incorporate veral populations derived from three or more parents and also can be ud to handle different mating designs[21].In this last years,many studies of QTL analys for agronomical traits of interest have been carried out uncatula such as tolerance to drought stress[22],aerial morphogenesis[23],flowering date[24],resistance to Aphanomyces euteiches[25],ed mineral concentration and content[26],salt tolerance[27],ed germination and pre-emergence growth at extreme temperatures [28]and in water deficit[29].
The study reported in this paper aims to identify and map QTL associated with Na+and K+contents in the leaves,stems and roots controlling salt tolerance uncatula using Jemalong A17×F83005.5RILs population(LR5).We map and discuss veral loci explaining the variability of the physiological traits in0and 50mM NaCl conditions,at a vegetative stage.
2.Results
2.1.Phenotypic variation and correlations among traits
Analysis of variance revealed that variation between the RILs for leaf,stem and root dry weights and their concentrations of Na+and K+was dependent on line,treatment,and line by treatment interac-tion effects(Table1).Salt stress treatment explained most of the trait variation.Thisfinding indicates a difference among the RILs in the respons to environmental conditions.
In control conditions,fewer values were found for F83line for StNa,LeaNa,RoNa,StK,LeaK,RoK,StNaK,LeaNaK,and RoNaK,while the largest values were for JA17for StNa,LeaNa,RoNa,StNaK,LeaNaK and RoNaK traits under salt-stresd conditions.
To estimate the importance of measured traits in the description of the obrved phenotypic variability between analyzed RILs,we measure broad-n heritability(H²)of the traits.Biomass traits showed higher broad-n heritability(H²)in control than in salt treatment,and heritability was higher for StDW and LeaDW.Further-more,heritability values for traits relative to stems,leaf and root Na+ and K+uptake are low to moderate.
Proprieties of the trait distribution were estimated by ANOVA analysis over4replicates.According to Kurtosis and Skewness estimation trait distribution reflects the variability obrved between studied lines.Physiological values in the whole population show a relatively normal distribution around a pop
ulation mean that lies between the parental values.Some RILs had more extreme values than the parental lines showing a transgressive gregation;this is obvious for all traits under control and salt-stresd conditions (Table2).
Correlations between measured traits showed29and39of72 possible correlations were significant in control and50mM NaCl conditions,respectively(Table3).Fourteen(14)of the29,and17 of the39correlations were positive.Our results showed that the sign and level of correlations between measured traits were generally influenced by NaCl stress application.Indeed,some traits showed significant correlations in control which become highly significant in NaCl treatment,and there are ones which explain contrary.A strong positive correlation was obrved between leaf,stem and root dry weights.Negative associations were obrved between dry weights(leaves,stems and roots)with Na+and K+contents.On the other hand,Na+and K+concentrations in leaves and stems were positively correlated.
2.2.QTL mapping
QTL mapping results are summarized in Table4,where the name of QTL contains the trait name suffixed with the type of treatment and an ordering number from thefirst chromosome.A total of13 QT
Ls on8linkage groups were detected for measured traits in control and salt treatments.Six of the QTLs were identified in control treatment,two in salt stress conditions andfive relative to the nsitivity index.The percentage of phenotypic variance explained by a single QTL(R²)ranged from9.5to12.5%of the phenotypic variation.We mapped three QTLs for root Na+/K+ratio concentration under control treatment on chromosomes1and8,and one QTL for leaf Na+/K+under salt conditions on chromosome1.One QTL for stem Na+concentration under control conditions was detected on chromo-some2,one QTL for stem Na+total quantity under control conditions was on chromosome3,and one QTL for leaf Na+total quantity under control conditions was mapped on chromosome1.One QTL has been identified for root K+total quantity under salt condition on chromo-some8.Furthermore,five QTLs relative to nsitivity index were detected,which one for stem K+concentration identified on chromo-some4,three for leaf K+concentration were mapped on chromo-somes1and2and one for root K+concentration detected on chromosome7.Six QTLs were detected on chromosome1,two QTLs were on each chromosome2and8and one QTL on each chromosome 3,4and7.No QTL was found on chromosomes5and6.The chromo-some1emed to be highly involved in the genetic variation of leaf and root Na+/K+ratio concentration between RILs of LR5under control and salt-stresd conditions.Overall,no major QTL was identified for measured traits which may be due to the fact that many genes with small effects gregate in this population.
For an easier overview of overlapping QTL between traits and growth conditions,QTL regions are illustrated in Fig.1.Both parental lines contributed to the expression of the different target traits.No overlapping QTLs was found for measured traits under control and salt-stresd conditions(Table4and Fig.1),except tho relative to leaf Na+/K+ratio concentration,leaf Na+total quantity and leaf K+ concentration nsitivity index traits on chromosome1.Among the six QTLs detected under control conditions,no QTL was mapped under salt-stresd conditions.
3.Discussion
3.1.Phenotypic variation and correlations among traits
The line by treatment effect on stem and leaf dry weights,and root Na+/K+content suggests that the relative performance of genotype (especially RILs)changed depending on environmental conditions. Thisfinding makes asssing the causal relationship between genotype and phenotype difficult.Similarly,this result was also reported for a RIL population of rice(Bala×Azucena mapping population)where a QTL×environment interaction was obrved[30].The effect of environmen-tal conditions has to be tested on a range of genotypes,as genotypes×environment interactions are likely to be detected.Genotype×environment interaction is a common characteristic for quantitative tr
aits,and has been a subject of great concern for breeding programs. The marker assisted lection is generally more efficient than pheno-typic lection in the prence of genotype×environment interac-tion[31].Thus,the challenge is to define phenotypes that are a true reflection of the genotypic differences,and tofind the right genes/ phenotypes that work well in target environments.
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All the trait distributions were continuous and had a normal distribution in the control and NaCl treatments,indicating polygenic gregation or monogenic gregation with a high error effect.All measured traits for RILs showed signi ficant transgressive gregations with values either larger or smaller than tho of the parents.Similarly,of the transgressive gregation obrved at the phenotypic level of studied population,signi ficant transgressive gregations were reported for physiological traits in rice [19],and for morphological traits in Arabidopsis under contrasting nitrate availability in the soil [32],in sun flower under drought stress [33],and in durum wheat under water de ficit [34].
Heritabilities estimation of measured traits relative to dry weight,showed higher values (H 2)in control
mrh
than under salt-stresd condi-tions (Table 1).But traits relative to leaf,stem and root Na +and K +contents emed to be moderately heritable.This finding is due to a higher genetic variance for StDW,LeaDW and RoDW under control conditions and to a higher environmental variance for the remaining traits under salt treatment.Similarly,this result was also mentioned under drought conditions and many studies found moderate heritability of yield [35].
Our results showed that NaCl stress application in fluences most of negative correlations between measured traits under control and salt-stresd conditions.A strong positive correlation was obrved between leaf,stem and root dry weights.The positive correlations found between ion concentration ratio in root and stem,leaves and root dry weights suggest that tolerant lines are tho who are able to maintain low levels of root Na +/K +concentration ratio in their leaves.Similarly,shoot and root dry weight showed low correlation with Na +,K +concentration and Na +/K +ratio in rice (Oryza sativa L)in salt conditions [36].Indeed,this suggestion supports the notion that excess Na +was the primary cau of salt nsitivity in non-halophytes [12].Moreover,shoot Na +accumulation and salt tolerance were not correlated in bread wheat,asssing that salinity tolerance would be identi fied by tissue tolerance [37].
On the other hand,this obrved variability of salt stress respon between studied lines able us to u
nderstand salt stress respon by mapping QTL which can identify chromosomes regions which could be responsible.Many studies focus on salt tolerance of this species,like study which compared the differential root growth of two genotypes uncatula (108-R and Jemalong A17)in respon to salt stress.Jemalong A17was more tolerant to salt stress than 108-R,where it grew well at high salinity levels (120mM NaCl)[38].Transcription factor gene after salt stress uncatula roots was analyzed for this line and it was suggested that spatial differences of transcription factor gene regulation by environmental stress in various root regions may be crucial for the adaptation of their growth to speci fic soil environments [39].
3.2.QTL mapping
不可救药A moderate number of QTL on 6of the 8linkage groups were detected for leaf,stem and root Na +and K +uptake in control and salt-stresd conditions.Nevertheless,this work gives access to an interesting part of the genetic variation of salt-stresd respon in the JA17×F83population.Furthermore,most of detected QTLs were mapped under control treatment.By contrast,more QTLs were detected for morph-physiological traits related to drought tolerance in rice (O.sativa )under stress conditions [40].Similarly,among the 24QTLs detected under well-watered treatment,5(about 21%)were also detected under water-stresd conditions in sun flower [33].In the
prent study,among the 6QTLs detected under control treatment,no QTL was detected under salt-stresd conditions (Table 4).We postulate that the loci that are not stable across treatments re flect adaptation to this constraint.Indeed,the comparison between QTLs obtained in control and stresd treatments could allow the distinc-tion between constitutive and adaptive behaviors [41,33,40].
In
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accordance with [19],our results showed that detected QTLs for traits measured on the leaves and the roots did not share the same map loca-tions,suggesting that the genes controlling the transport of Na +and K +between the leaves and the roots may be different or induced unco-ordinatedly by salt stress.The process of Na +and K +uptake in rice were considered to be independent under salt stress [42].The uptake of Na +and K +maybe be independent [17],due to the major pathways of Na +and K +uptake in rice occur in parallel and not directly in competi-tion.K +is detrimental for Na +plant tolerance due to the fact that K +and Na +are chemically very similar.Other studies,reported that SOS (for salt overly nsitive)genes,SOS1,SOS2and SOS3in Arabidopsis ,were postulated to encode regulatory components controlling plant K +nutrition which in turn was esntial for salt tolerance,and considered that K +nutrition correlated cloly with salt tolerance in salt stress [43].
In this study we identi fied also five QTLs according to the nsitivity index for only K +content in leaves,stems and roots.This result con firms the importance of this ion in plant growth.However,plant
s need a small amount but high concentration of K +for speci fic functions in the cyto-plasm and a major portion (∼90%)of it is localized in vacuoles,where it acts as an osmoticum [44].On the other hand,no major QTL was iden-ti fied for measured traits which may be due to the fact that many genes with small effects gregate in this population.Similarly,complex phys-iological traits have on recent occasions been described by a small num-ber of major QTLs [19,15].The QTLs identi fied in the prent study underlined that veral putative genomic regions are involved in the re-spon of leaves,stem and roots Na +and K +uptake traits under control and salt-stresd treatments (Table 4).Accordingly,numerous studies have reported the polygenic determinism of shoot and stem Na +and K +concentrations in rice [17,19],in tomato [15],in Arabidopsis [45],and in cereals [46].This polygenic feature of plant's respon to salt stress makes it dif ficult to transfer individual genes using traditional plant breeding or marker-assisted lection (MAS).
Most of the identi fied QTLs did not share the same locations on the LR5genetic map suggesting their adaptation to this constraint.The nsitivity to environmental conditions may be due to the respon-siveness of regulation (anscription)of the QTL gene to an
environmental cue.Our results will provide important information for further functional analysis of salt-tolerance genes uncatula .Detailed characterization of the QTLs regions through the devel
op-ment and evaluation of near-isogenic lines will lead to an improved understanding of salt tolerance and might t the stage for the positional cloning of salt tolerance genes.As the QTLs found here are relatively weak and they were identi fied from greenhou study,their ufulness should therefore be evaluated under field condition,and also validated in other genetic backgrounds.
In the light of our previous results on QTLs mapping for morpholog-ical traits of LR5population [27],few common QTLs,with this study,were identi fied for measured traits under salt stress on chromosomes 3and 8,suggesting that genetic bas for tolerance to both traits could be different.The high number of QTLs for physiological and morpholog-ical traits was detected on chromosomes 1and 8.Furthermore,QTLs found for LR5population related to final percentage of germination and for early embryonic axis elongation rate for LR4in chromosome 3[28]at respectively sub-optimal and supra optimal temperatures,are co-located with tho identi fied in this study concerning stem Na +total quantity and length of orthotropic axis in [27].It remains to be investigated whether the co-locations of the QTLs are caud by the prence of cloly linked genes or by pleiotropic effects from the same genes on the traits.4.Material and methods
4.1.Plant material and experimental conditions
ppf
A gregating population LR5of Recombinant Inbred Lines (133RILs)uncatula at F 8generation derived from a cross between Jemalong A17(JA17)and F83005.5(F83)was ud.RILs were devel-oped by single-ed descent until the F 8generation at the INP-ENSAT,France.The two parents were included in all experiments.Seed germination was performed using mechanic scari fication and NaClO 12%as agent for ed surface sterilization.The soaked eds have been sown in Petri dishes on 0.9%agar medium before being
Table 2
Dry weight and stem,leaf and root Na +,K +content in the LR5population (JemalongA17×F83005.5)uncatula under control and salt-stresd conditions.Traits
Treatment
when you goneParental lines Recombinant Inbred Lines JemalongA17
F83005.5Means Std dev Range
Skewness Kurtosis StDw Control
0.520.390.340.130.11–0.87 1.18 1.79LeaDw 0.640.610.430.140.18–1.000.930.91RoDw 0.37
0.38
0.28
0.120.09–0.86
4.5334.17StNa 12,990.3711,776.1512,16
5.034028.136132.54–44,547.929.85130.26LeaNa 9282.459642.8310,45
6.21290
7.42185
8.68–20,876.95 1.86 6.28RoNa 12,858.3517,300.9211,671.94054.024354.61–30,121.38 1.49 4.65StK 34,386.7238,980.9740,517.0810,513.823432.27–89,78
9.8514.17234.11LeaK 27,884.1328,315.0734,151.937192.1912,414.37–64,354.81 1.82 4.67RoK 17,646.0717,848.1422,229.487339.889060.25–54,782.95
0.85 1.79StNaK 0.390.310.320.130.09–1.2814.17234.11LeaNaK 0.340.340.320.090.07–0.63 1.82
4.67RoNaK 0.740.970.560.310.30-3.63
11.44189.24StDw NaCl
0.150.140.170.050.06–0.390.480.65LeaDw 0.290.30.320.070.15–0.630.12−0.16RoDw 0.2
disillusion0.19
0.2
0.090.05–0.76
5.857StNa 27,20
6.2136,965.0334,755.888963.9617,120.43–91,809.9710.45169.99LeaNa 17,505.7319,31
7.0930,2394817.4418,697.85–43,762.520.760.96RoNa 28,847.6229,196.9917,669.475000.364697.36–36,652.87 3.7231.02StK 31,926.3144,183.5629,922.3210,192.9116,884.80–126,200.449.76139.16LeaK 25,460.7937,471.4121,620.343355.2112,613.90–35,851.27 1.87.03RoK 17,412.3418,496.9626,237.028885.47665.11–81,465.87
12.86221.15StNaK 0.850.830.940.410.41–4.369.76139.16LeaNaK 0.690.520.750.160.42–1.24 1.87.03RoNaK
1.74
1.63
1.64
0.57
0.78–6.28
4.82
42.87
Std dev:standard deviation.Stem dry weight (StDW,g),leaf dry weight (LeaDW,g),root dry weight (RoDW,g),stem K +concentration (StK,μmol mg −1of stem dry weight),leaf K +concentration (LeaK,μmol mg −1of leaf dry weight),and root K +concentration (RoK,μmol mg −1of root dry weight),
stem Na +concentration (StNa,μmol mg −1of stem dry weight),leaf Na +concentration (LeaNa,μmol mg −1of leaf dry weight),root Na +concentration (RoNa,μmol mg −1of root dry weight),stem Na +/K +concentration ratio (StNaK),leaf Na +/K +concentration ratio (LeaNaK),and root Na +/K +concentration ratio (RoNaK).
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vernalized at4°C for72h.Once the emerging root attained a length of4mm,edlings were individually transferred to33centiliters pots(8cm diameter and10.5cm deep)filled with sterilized sand using chlorhydric acid0.05%.Each plant was grown in an individual pot in greenhou in controlled conditions with a temperature of 25°C,a relative humidity of80%and a photoperiod of16/8h.Four replicates per line and per treatment were ud.The experimental design was completely randomized.During60days,the plants were irrigated2times per week.For control treatment,we ud a nutritive solution as described by[47]whereas the iron source was modified by adding Fe-EDTA.In salt stress treatment,we added50mM of NaCl to the nutritive solution.Salt stress was applied at edling stage directly after germination.For both treatments,the whole retention capacity was maint
ained by weighting pots and adding the nutritive solution to compensate the decrea in volume.To overcome NaCl accumulation problem in the substrate,sand in the pots was washed by distilled water2times per week.
4.2.Trait measurement
The harvest of plants was performed60days after the beginning of the experiment.At harvest,we measured venteen quantitative and physiological traits of the stem dry weight(StDW),leaf dry weight (LeaDW),root dry weight(RoDW),stem Na+concentration(StNaC), stem Na+total quantity(StNaTQ),leaf Na+concentration(LeaNaC), leaf Na+total quantity(LeaNaTQ),root Na+concentration(RoNaC), root Na+total quantity(RoNaTQ),stem K+concentration(StKC),stem K+total quantity(StKTQ),leaf K+concentration(LeaKC),leaf K+total quantity(LeaKTQ),root K+concentration(RoKC),root K+total quantity (RoKTQ),Na+/K+concentration ratio(Na+/K+C),and Na+/K+total
Table3
Estimated correlations between measured traits for RILs of uncatula under control and salt-stresd conditions.
StDW LeaDW RoDW StNa LeaNa RoNa StK LeaK RoK StNaK LeaNaK RoNaK
Control treatment
StDW 1.000
LeaDW0.741⁎⁎⁎ 1.000
RoDW0.415⁎⁎⁎0.319⁎⁎⁎ 1.000
StNa 1.000
LeaNa−0.159⁎⁎0.195⁎⁎⁎ 1.000
RoNa−0.115⁎−0.371⁎⁎⁎ 1.000
StK−0.237⁎⁎⁎−0.133⁎⁎0.225⁎⁎⁎ 1.000
LeaK−0.127⁎0.246⁎⁎⁎−0.182⁎⁎⁎0.224⁎⁎⁎ 1.000
RoK−0.352⁎⁎⁎−0.297⁎⁎⁎−0.500⁎⁎⁎0.660⁎⁎⁎ 1.000
StNaK0.340⁎⁎⁎−0.196⁎⁎⁎ 1.000
LeaNaK−0.133⁎⁎0.700⁎⁎⁎−0.146⁎⁎−0.392⁎⁎⁎0.105⁎ 1.000
RoNaK0.147⁎⁎0.178⁎⁎⁎0.436⁎⁎⁎−0.188⁎⁎⁎ 1.000
NaCl treatment
StDW 1.000
LeaDW0.753⁎⁎⁎ 1.000
RoDW0.282⁎⁎⁎0.313⁎⁎⁎ 1.000
StNa−0.161⁎⁎−0.223⁎⁎⁎ 1.000
LeaNa−0.349⁎⁎⁎−0.374⁎⁎⁎−0.212⁎⁎⁎0.232⁎⁎⁎ 1.000
RoNa−0.269⁎⁎⁎−0.125⁎ 1.000
StK−0.244⁎⁎⁎−0.326⁎⁎⁎0.277⁎⁎⁎0.196⁎⁎⁎−0.126⁎ 1.000
LeaK−0.127⁎−0.132⁎⁎0.357⁎⁎⁎0.149⁎⁎ 1.000
RoK−0.148⁎⁎−0.146⁎⁎−0.370⁎⁎⁎0.561⁎⁎⁎ 1.000
StNaK0.741⁎⁎⁎−0.292⁎⁎⁎ 1.000
LeaNaK−0.212⁎⁎⁎−0.226⁎⁎⁎−0.183⁎⁎⁎0.202⁎⁎⁎0.625⁎⁎⁎−0.428⁎⁎⁎0.151⁎⁎ 1.000
RoNaK0.189⁎⁎⁎0.175⁎⁎⁎0.103⁎0.364⁎⁎⁎−0.313⁎⁎⁎−0.147⁎⁎ 1.000
linakSignificance levels;*P b=0.05,**P b=0.01,***P b=0.001.Stem dry weight(StDW),leaf dry weight(LeaDW),root dry weight(RoDW),stem Na+concentration(StNa),leaf Na+ concentration(LeaNa),root Na+concentration(RoNa),stem K+concentration(StK),leaf K+concentration(LeaK),root K+concentration(RoK),stem Na+/K+concentration ratio (StNaK),leaf Na+/K+concentration ratio(LeaNaK),and root Na+/K+concentration ratio(RoNaK).
Table4
Map positions and genetic effect of putative QTLs detected for measured traits in Recombinant Inbred Lines uncatula in control and50mM of NaCl treatment.
Traits Treatment QTLs a Linkage group Left marker QTL position and
confidence interval(cM)
LOD Effect b R2(%)
Stem Na+concentration Control StNaCct.2II MTE1442(40–46) 3.632090.55911.9 Root Na+/K+concentration ratio Control RoNaKCct.1I MTE7754(48–56) 3.020.15610.0archers
RoNaKCct.1I MTE666(64–70) 2.85−0.1549.5
vramRoNaKCct.1VIII MTE9434(26–46) 2.88−0.1059.6 Stem Na+total quantity Control StNaTQct.3III MTE1926(22–32) 2.9360.8389.7 Leaf Na+total quantity Control LeaNaTQct.1I MTE7510(4–14) 3.2244.79810.8 Leaf Na+/K+concentration ratio NaCl LeaNaKCsl.1I MTE412(4–24) 2.980.0559.8 Root K+total quantity NaCl RoKTQsl.8VIII MTE9426(20–34) 3.01−58.0349.9 Stem K+concentration Sensitivity Index StKCsi.4IV MTE2950(42–68) 3.82−11.27412.5 Leaf K+concentration Sensitivity Index LeaKCsi.1I MTE7510(6–20) 3.49−10.19011.7
LeaKCsi.1I MTE8878(74–78) 2.9013.2149.6
LeaKCsi.2II MTE7250(48–56) 3.5415.21511.7 Root K+concentration Sensitivity Index RoKCsi.7VII MTE6946(36–54) 3.0812.80710.2
a The name of QTL contains the trait name suffixed with the type of treatment and an ordering number from thefirst linkage group,Control(ct),NaCl treatment(sl),Sensitivity index(si).
b Effect of Jemalong A17allele for Jemalong A17x F83005.5population.
122S.Arraouadi et al./Genomics99(2012)118–125
