Global carrot production is limited by the crop’s high susceptibility to salinity stress. Not much public research has been conducted to screen for genetic salinity stress tolerance in carrot, and few resources exist to aid plant breeders in improving salinity tolerance in carrot. The objectives of this study were to evaluate the response of diverse carrot germplasm to salinity stress, identify salt-tolerant carrot germplasm that may be used by breeders, and define appropriate screening criteria for assessing salt tolerance in germinating carrot seed. Carrot plant introductions (PIs) (n = 273) from the U.S. Department of Agriculture (USDA) National Plant Germplasm System representing 41 different countries, inbred lines from the USDA Agricultural Research Service (n = 16), and widely grown commercial hybrids (n = 5) were screened for salinity tolerance under salinity stress and nonstress conditions (150 and 0 mm NaCl, respectively) by measuring the absolute decrease (AD) in the percent of germination, inhibition index (II), relative salt tolerance (RST), and salt tolerance index (STI) of germinating seeds. All salt tolerance measurements differed significantly between accessions; AD ranged from −4.2% to 93.0%; II ranged from −8.0% to 100.0%; RST ranged from 0.0 to 1.08; and STI ranged from 0.0 to 1.38. Broad sense heritability calculations for these measurements were 0.87 or more, indicating a strong genetic contribution to the variation observed. Six accessions identified as salt-tolerant or salt-susceptible were evaluated in a subsequent experiment conducted at salt concentrations of 0, 50, 100, 150, 200, and 250 mm NaCl. Variations between mean AD, II, RST, and STI of tolerant and susceptible lines were greatest at 150 mm NaCl, validating the use of 150 mm NaCl concentrations during salt tolerance screening of carrot seed. Wild carrot accessions displayed little tolerance, and PI 256066, PI 652253, PI 652402, and PI 652405 from Turkey were most salt-tolerant.
We thank the Global Crop Diversity Trust Project GS14014 for providing financial support. We also thank Kathleen Reitsma and the USDA National Germplasm System for their capable assistance and for providing the plant introduction carrot collection accessions.
BatesD.MaechlerM.BolkerB.WalkerS.ChristensenR.H.B.SingmannH.DaiB.ScheiplF.GrothendieckG.GreenP.2018Linear mixed-effects models using 'Eigen' and S4. R. package version 17 p. 42–44
BaxterI.BrazeltonJ.N.YuD.HuangY.S.LahnerB.YakubovaE.LiY.BergelsonJ.BorevitzJ.O.NordborgM.VitekO.SaltD.E.2010A coastal cline in sodium accumulation in Arabidopsis thaliana is driven by natural variation of the sodium transporter AtHKT1;1PLoS Genet.611e1001193
Baxter,I.Brazelton,J.N.Yu,D.Huang,Y.S.Lahner,B.Yakubova,E.Li,Y.Bergelson,J.Borevitz,J.O.Nordborg,M.Vitek,O.Salt,D.E.2010A coastal cline in sodium accumulation in Arabidopsis thaliana is driven by natural variation of the sodium transporter AtHKT1;1611e1001193)| false
IorizzoM.SenalikD.A.EllisonS.L.GrzebelusD.CavagnaroP.F.AllenderC.BrunetJ.SpoonerD.M.DeynzeA.V.SimonP.W.2013Genetic structure and domestication of carrot (Daucus carota subsp. sativus) (Apiaceae)Amer. J. Bot.1005930938
Iorizzo,M.Senalik,D.A.Ellison,S.L.Grzebelus,D.Cavagnaro,P.F.Allender,C.Brunet,J.Spooner,D.M.Deynze,A.V.Simon,P.W.2013Genetic structure and domestication of carrot (Daucus carota subsp. sativus) (Apiaceae)1005930938)| false
KahouliB.BorgiZ.HannachiC.2014Effect of sodium chloride on the germination of the seeds of a collection of carrot accessions (Daucus carota L.) cultivated in the region of Sidi BouzidJ. Stress Physiol. Biochem.1032836
Kahouli,B.Borgi,Z.Hannachi,C.2014Effect of sodium chloride on the germination of the seeds of a collection of carrot accessions (Daucus carota L.) cultivated in the region of Sidi Bouzid1032836)| false
KhouryC.K.Castañeda-AlvarezN.P.AchicanoyH.A.SosaC.C.BernauV.KassaM.T.NortonS.L.van der MaesenL.J.G.UpadhyayaH.D.Ramírez-VillegasJ.JarvisA.StruikP.C.2015Crop wild relatives of pigeonpea [Cajanus cajan (L.) Millsp.]: Distributions, ex situ conservation status, and potential genetic resources for abiotic stress toleranceBiol. Conserv.184259270
Khoury,C.K.Castañeda-Alvarez,N.P.Achicanoy,H.A.Sosa,C.C.Bernau,V.Kassa,M.T.Norton,S.L.van der Maesen,L.J.G.Upadhyaya,H.D.Ramírez-Villegas,J.Jarvis,A.Struik,P.C.2015Crop wild relatives of pigeonpea [Cajanus cajan (L.) Millsp.]: Distributions, ex situ conservation status, and potential genetic resources for abiotic stress tolerance184259270)| false
R Core Team2018R: A language and environment for statistical computing. R Foundation for Statistical Computing Vienna Austria
RavelombolaW.ShiA.WengY.MouB.MotesD.ClarkJ.ChenP.SrivastavaV.QinJ.DongL.YangW.BhattaraiG.SugiharaY.2018Association analysis of salt tolerance in cowpea (Vigna unguiculata (L.) Walp) at germination and seedling stagesTheor. Appl. Genet.13117991
Ravelombola,W.Shi,A.Weng,Y.Mou,B.Motes,D.Clark,J.Chen,P.Srivastava,V.Qin,J.Dong,L.Yang,W.Bhattarai,G.Sugihara,Y.2018Association analysis of salt tolerance in cowpea (Vigna unguiculata (L.) Walp) at germination and seedling stages13117991)| false