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Euphytica 115: 221–224, 2000. © 2000 Kluwer Academic Publishers. Printed in the Netherlands. 221 Chromosomal location of resistance to Septoria tritici in Hordeum chilense determined by the study of chromosomal addition and substitution lines in ‘Chinese Spring’ wheat D. Rubiales 1 , S.M. Reader 2 & A. Mart´ın 1 1 Institute of Sustainable Agriculture, CSIC, Apdo. 4084, E-14080 C´ ordoba, Spain; 2 John Innes Centre, Norwich Research Park, Colney, Norwich, NR4 UH, U.K. Received 16 Septem
   Euphytica  115:  221–224, 2000.© 2000  Kluwer Academic Publishers. Printed in the Netherlands.  221 Chromosomal location of resistance to  Septoria tritici  in  Hordeum chilense determined by the study of chromosomal addition and substitution lines in‘Chinese Spring’ wheat D. Rubiales 1 , S.M. Reader 2 & A. Mart´ın 1 1  Institute of Sustainable Agriculture, CSIC, Apdo. 4084, E-14080 C´ ordoba, Spain;  2  John Innes Centre, Norwich Research Park, Colney, Norwich, NR4 UH, U.K. Received 16 September 1999; accepted 13 February 2000 Key words: Septoria tritici , disease resistance,  Hordeum chilense , Tritordeum Summary  Hordeumchilense exhibitsresistanceto Septoriatritici . Additionandsubstitutionlinesof   H.chilense inwheatwereutilized in growth chamber and field experiments to determine which  H. chilense  chromosomes carry resistancegenes. Resistance is conferred by gene(s) on chromosome 4 and, to a minor extent, by genes on chromosomes 5, 6and 7. Introduction Septoria tritici  blotch of wheat incited by  My-cosphaerella graminicola  (Fuckel) J. Schröt in Cohn(anamorph  Septoria tritici  Roberge in Desmaz.) is amajor wheat disease in many parts of the world caus-ing severe losses in yield. Breeding for host resistanceis consideredthe maindefenceagainstthis disease andseveral sources of resistance have yielded adequateprotection. A gradual but steady increase in sept-oria leaf blotch resistance has been reported in springwheat since the 1970s (Dubin & Rajaram, 1996).Sexualreproductionin  M.graminicola allowsnewvir-ulence combinations and as a consequence the patho-gen may respond over time to selection exerted by theintroduction of host resistance genes. Resistant ger-mplasm is not abundant (Eyal et al., 1987)and declinein the effectiveness of resistance has been reported(Ahmed et al., 1996; Kema et al., 1996; Mundt et al.,1999), although at slower rates than experienced withrusts and mildews due to the lower efficiency in dis-seminationof new individuals.Broadeningthe geneticbase of cultivated wheat by the introgression of resist-ancegenes fromrelated species orgeneramay provideadditional possibilities to achieve adequate resistanceagainst septoria. Resistance has been identified in  Ae-gilops tauschii  and  Thynopyrum elongatum  (Dubin &Rajaram, 1996)and  Hordeumchilense (Rubialesetal.,1992).  H. chilense  is a wild barley that has been suc-cessfully hybridizedwith both durumand bread wheat(Martinet al., 1996).Amongseveralapproachesforitsuse in cereal breeding are the development of hybridsand amphiploids with wheat to be used as a possiblenew crop, named tritordeum, or as bridges to transferuseful genes to cultivated cereals (Martín & Cubero,1981; Miller et al., 1982; Fernández & Jouve, 1988).The purposeof the presentstudy was to identify the  H.chilense  chromosome(s) responsible for the resistanceto septoria tritici blotch, and to assess the feasibility of transferring the resistance to wheat. Materials and methods The  H. chilense  addition and substitution lines usedin this study are maintained at the John Innes Centre,Norwich, UK. The chromosome nomenclature in thispaper is based on homoeology. The plant materialused was as follows: bread wheat ‘Chinese Spring’(CS) (2n=6x=42, AABBDD),  H. chilense  accessionH1 (4010001) (2n=2x=14; H ch H ch ), the ‘CS’/   H.chilense  ditelosomic addition lines 1H ch S, 2H ch α ,5H ch α , 6H ch S, 7H ch α  and 7H ch β  (2n=42+2 t  ), themonosomic 1H ch monotelosomic 1H ch S addition line  222(2n=43+ t  ); and the disomic addition lines for chro-mosomes 4H ch , 5H ch , 6H ch and 7H ch (2n=42+2),The substitution fines studied were those describedin Table 2. The selfed progenies of cytologicallymonitored plants were used in the evaluations. Seedling test  Seedlings of the addition and substitution lines werestudied for their response to septoria tritici blotchin seven consecutive replicates. Each replicate con-sisted of 5–6 seedlings/accession. Standard suscept-ible wheats as well as the parental wheat ChineseSpring and  H. chilense  accession H1 were included.Plants were inoculated in the two leaf stage bysprayingwith a suspensionof 10 6 conidia/ml of a bulk collection of   S. tritici  collected on bread wheat at Cór-doba. After inoculation, the pots were randomized intrays and kept at room temperature until the leaveswere dry. Plants were incubated in the dark at 20  ◦ Cand 100% RH for 48 hours and then transferred to agrowth chamber under the same temperature with alight regime of 14 hours at 10.000 lux.The first and second leaves of individual plantswere assessed for percentage of pycnidia coverage 21days after inoculation. Field test  The fines were grown in nursery rows, 5 plants/row,in Córdoba in 1998–99 field trials with 3 replications.The trials were inoculated several times with the samepopulationasaboveduringtilleringusingasuspensionof 10 7 conidia/ml. In order to ensure the developmentof disease the plants were irrigated with sprinklers.The field tests were scored for Disease Severity (DS)at the grain filling stage. The scores were angulartransformedpriorto an analysisof varianceusing SASversion 6.03 (SAS Institute Inc. Cary, NC, USA). Results and discussion The accession of   H. chilense  used in the productionof the chromosome addition lines is highly resistantto all the isolates of   S. tritici  studied (Rubiales et al.,1992).The CS/   H. chilense  chromosome4H ch disomicaddition line showed the highest level of resistance toinfection by  S. tritici , both in seedlings and in adultplant stages (Table 1). That was also the case forthe two substitution lines carrying chromosome 4H ch (Table 2). The level of resistance conferred by this Table 1.  Percentages of pycnidia coverage in seedlingsand adult plants of wheat ‘Chinese Spring’ (CS),  Hordeumchilense  and CS/   Hordeum chilense  single chromosomeaddition lines inoculated with  Septoria tritici Line % pynidia coverageSeedlings FieldChinese Spring 40 a 40 a  H. chilense  H1 0 d 0 cCS/4H ch disomic 1 d 0.3 cCS/5H ch disomic 14 bcd 25 abCS/6H ch disomic 15 bcd 17bCS/7H ch disomic 9 cd 20 bCS/1H ch S monosomic 1H ch +monotelosomic 1H ch S 32 ab 23 abCS/1H ch S ditelosomic 26 abc 30 abCS/2H ch α  ditelosomic 24 abc – 1 CS/5H ch L ditelosomic 14 bcd 23 abCS/6H ch S ditelosomic 4 d 17 bCSS/7H ch α  ditelosomic 14 bcd 20 abCS/7H ch β  ditelosomic 17 abcd 27 ab 1 Not tested. 2 Letters in common within a column indicate that differ-ences are not statistically significant at  p  = 0 . 05. Table 2.  Percentages of pycnidia coverage inseedlings of wheat ‘Chinese Spring’ (CS),  Hordeum chilense  and CS/   Hordeum chilense single chromosome substitution and translocationlines inoculated with  Septoria tritici Line % pycnidia coverageChinese Spring (CS) 34 bc  H. chilense  H1 0 f CS (1A)/1H ch 40 bCS 1BL/1H ch S 34 bcCS (4B)/4H ch 7 ef CS (4D)/4H ch 0.3 f CS (5A)/5H ch 23 cdCS (5B)/5H ch 17 deCS (5D)/5H ch 32 bcdCS (6A)/6H ch S 60 aCS (7A)/7H ch 68 aCS (7A)/7H ch α ditelo 68 aCS (7B)/7H ch 58 aCS (7B)/7H ch β ditelo 62 aCS (7D)/7H ch 67 aCS (7D)/7H ch α ditelo 62 aLetters in common within a column indicate thatdifferences are not statistically significant att  p  = 0 . 05.  223chromosome was sufficiently high to be obvious inevery single plant.SCARs specific for selection of   H. chilense  chro-mosomes in a wheat background have been produced(Hernández et al., 1999) making marker selectedbreeding with the complete chromosome 4H ch a pos-sibility in bread and durum wheat. We have thusinitiated the process of introgressing an intact 4H ch chromosome, and SCARs will also be similarly em-ployed to facilitate the production of resistant recom-binants between the group 4 chromosomes of wheatand 4H ch .Addition lines with the long arm of chromosome5H ch , the short arm of 6H ch and both arms of 7H ch were also more resistant at the seedling stage althoughresistance was slightly reducedat the adult plant stage.However, substitution lines carrying these chromo-somes were susceptible. An explanation could be thatthe chromosomes 6A, 7A, 7B and 7D of wheat mayconfer a degree of resistance to septoria tritici blotchand their absence results in increased susceptibility.This could be elucidated using aneuploid stocks of wheat. Similar results demonstrating the presumedcontribution of chromosomes from both the donor  Ae-gilops tauschii  and the recipient wheat line to theresistance to septoria nodorum blotch was obtainedby Nicholson et al. (1993). Furthermore, if any suchresistance gene(s)in wheat were foundto reside at dif-ferent loci to those of   H. chilense , then combining thetwo in suitable recombinantchromosomes may conferan enhanced level of resistance upon Tritordeum orwheat.We have observed some dosage effect of the res-istance of   H. chilense  in tritordeum (Rubiales etal., 1992). All hexaploid tritordeums (AABBH ch H ch )wereimmune,whereasresistance was partiallydilutedin some octoploid tritordeums (AABBDDH ch H ch ),perhapsbecauseofinteractionsbetweentheDandH ch genomes. Similarly, Rillo et al. (1970) observed anapparentdosage effect in the septoria tritici blotch res-istance of an  Agropyron -wheat derivative. The resist-ance was located on a single  Agropyron  chromosomeand the disomic addition plants were resistant at boththe seedling and adult plant stages, whereas the mono-somic and di-isosomic addition plants were resistantonly as seedlings. Apparently the intact  Agropyron chromosome must be in the disomic form to condi-tion high resistance at all stages of plant growth. Weonly studied the disomic addition line of chromosome4H ch , so can not postulate upon a possible dilution of the resistance in the monosomic form.The resistance conferred by chromosome 4H ch tobread wheat almost matched that of the donor  H.chilense  in both the disomic addition and the substitu-tionlines, andinbothseedlingsandmatureplants.Thehomoeologous group 4 chromosomes of bread wheatappear to have contributed little to the level of resist-ance (Table 2), thus it is possible that the resistance of 4H ch would also be expressed if a suitable recombin-ant chromosomewas introgressedinto a durumwheat.Thus, the  H. chilense  resistance could also be veryhelpful in durum wheat breeding.Resistance to septoria tritici blotch is commonlyassociated with lateness and tall plant stature (Eyalet al., 1987). However, the reduction in the levels of infections reported here must be due to true geneticalresistance(s) as is evident both in seedlings and adultplants, and there was no apparent correlation betweendisease severity in the field and plant stature.Although 4H ch appears to be responsible for mostof the resistance capability of the wheat lines in thesetests, it should be remembered that chromosomes 5,6 and 7 of   H. chilense  also confer varying degreesof resistance. An addition line of chromosome 3 of   H. chilense  has not been obtained, and thus couldnot be assessed in this study. The possibility of theoccurrence of additional resistance factors on thatchromosome cannot be excluded. Acknowledgements The authors acknowledge Ana Moral for her technicalassistance and the Spanish C.I.C.Y.T. Proj. AGF98-0945 and AGF99-1036 for the financial support. References Ahmed, H.U., C.C. Mundt, M.E. Hoffer & S.M. Coakley, 1996.Selective influence of wheat cultivars on pathogenicity of   My-cosphaerella graminicola  (anamorph  Septoria tritici ). Phyto-pathology 86: 454–458.Dubin, H.J. & S. Rajaram, 1996. Breeding disease-resistant wheatsfor tropical highlands and lowlands. Annu Rev Phytopathol 34:530–526.Fernández, J.A. & N. Jouve, 1988. The addition of   Hordeumchilense  chromosomes to  Triticum turgidum  conv.  durum : Bio-chemical, karyological and morphological characterization. Eu-phytica 37: 247–259.Eyal, Z., A.L. Scharen, J.M. Prescott & M. van Ginkel, 1987. The Septoria  Diseases of Wheat: Concepts and Methods of DiseaseManagement. CIMMYT, México.Hernández, P., A. Martín & G. Dorado, 1999. Development of SCARs by direct sequencing of RAPD products: a practical  224 tool for the introgression and marker-assisted selection of wheat.Molecular Breeding 5: 233–244.Kema, G.H.K, R. Sayoud, J.G. Annone & C.H. Van Silfhout,1996. Genetic variation for virulence and resistance in wheat-  Mycosphaerella graminicola  pathosystem II. Analysis of inter-actions between pathogen isolates and host cultivars. Phytopath-ology 86: 213–220.Martín, A. & J.I. Cubero, 1981. The use of   Hordeum chilense  incereal breeding. Cereal Res Comm 9: 317–323.Martín, A., C. Martínez-Araque, D. Rubiales & J. Ballesteros, 1996.Tritordeum: triticale’s new brother cereal. In: H. Guedes-Pintoet al. (Eds.), Triticale. Present and Future. Kluwer AcademicPublishers, Dordrecht.Miller, T.E., S.M. Reader & V. Chapman, 1982. The addition of   Hordeum chilense  chromosomes to wheat. In: Induced Variab-ility in Plant Breeding, pp, 79–81. Eucarpia, Int Symp 1981,Pudoc, Wageningen.Mundt C.C., M.E. Hoffer, H.U. Ahmed, S.M. Coakley, J.A. DiLe-one & C. Cowger, 1999. Population genetics and host resistance.In: J.A. Lucas, P. Bowyer & H.M. Anderson (Eds.),  Sept-oria  on Cereals: A Study of Pathosystems, pp. 115–130. CABIPublishing, Oxon, UK.Nicholson, P., H.N. Rezanoor & A.J. Worland, 1993. Chromo-somal location of resistance to  Septoria nodorum  in a synthetichexaploid wheat determined by the study of chromosomal sub-stitution lines in ‘Chinese Spring’ wheat. Plant Breeding 110:177–184.Rillo, A.O., R.M. CaldweH & D.V. Glover, 1970. Cytogeneticsof resistance to wheat leaf blotch ( Septorta tritici ) in backcrossderivatives of an Agroticum line. Crop Sci 10: 223–227.Rubiales, D., J. Ballesteros & A. Martín, 1992. Resistance to  Sept-oria tritici  in  Hordeum chilense  ×  Triumm  spp. amphiploids.Plant Breeding 109: 281–286.
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