Fine mapping and validation of a major locus for race non ... · RIL (left) and the resistance...
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Near-isogenic lines for the 1AS QTL The genotyping of the Avocet x Naxos RIL population identified one F 6 family (AxN-39) with heterozygous genotype calls for markers in the QTL area. Near-isogenic lines (NILS) were produced from heterozygous segregants for validation of the phenotypes in the field. As shown in Fig. 3, the QTL contributed to more than a 50% reduction in powdery mildew severity in this near-isogenic background. We then decided to develop a fine-mapping population based on this segregating F 6 family in order to mendelize the QTL. Introduction Powdery mildew, caused by Blumeria graminis f. sp. tritici is a major wheat disease in maritime and temperate climates. It can cause yield losses up to 40% if not properly controlled. Resistance breeding is considered a more sustainable and economic alternative to chemical disease control with fungicides. While race-specific resistance often is of short durability, long-lasting resistance can be achieved by combining several genes for partial, and race non-specific resistance. The German spring wheat cv. ‘Naxos’ shows a high level of partial resistance to powdery mildew in the field (Fig. 1), and in a previous study we identified a major QTL on 1AS with resistance from Naxos in the SHA3/CBRD x Naxos recombined inbred line (RIL) population based on QTL mapping with SSR and DArT markers (Lu et al. 2012). Validation with SNP markers Recently, we further refined the linkage maps with inclusion of SNP markers from the Illumina 90K wheat chip and narrowed down the QTL area. For validation, QTL mapping with 90K SNP markers was also done in the SORU#1 x Naxos population. Again, the 1AS QTL from Naxos was identified as a major determinant of powdery mildew resistance, explaining from 10 to 19% of the phenotypic variance in the field. The colinearity of common SNP markers confirmed that the QTL was the same in the two populations (Fig. 2, Windju et al. 2017). A third RIL population, Avocet x Naxos was phenotyped in the field and genotyped with KASP markers developed from the most significant 90K SNP markers on 1AS in SORU#1 x Naxos. The QTL was validated also in this population, and explained up to 10% of the phenotypic variance (data not shown). Acknowledgments This work has been funded through research grants from the Research Council of Norway. We are thankful to field technicians Cecilie Yri and Yalew Tarkegne for help with the field trials and lab engineer Anne Guri Marøy for the marker genotyping. Susanne S. Windju 1,2 , Keshav B. Malla 1,2,3 , Tatiana Belova 1 , Robert C. Wilson 3 , Jon Arne Dieseth 2 , Muath K. Alsheikh 1,2 , Morten Lillemo 1 1 Department of Plant Sciences, Norwegian University of Life Sciences, Post Box 5003, NO-1432 Ås, Norway; e-mail: [email protected] 2 Graminor AS, Hommelstadvegen 60, NO-2322 Ridabu, Norway 3 Faculty of Education and Natural Sciences, Inland Norway University of Applied Sciences, Post Box 400, NO-2418 Elverum, Norway Fine mapping and validation of a major locus for race non- specific partial resistance to powdery mildew on chromosome arm 1AS in the German spring wheat cv. ‘Naxos’ Fig. 2. Alignment of the linkage maps and corresponding LOD curves from the QTL mapping of powdery mildew resistance on 1AS in the two mapping populations SHA3/CBRD x Naxos and SORU#1 x Naxos. Fig. 1. Powdery mildew symptoms of a highly susceptible RIL (left) and the resistance source Naxos (right) in hillplots. 0 10 20 30 40 50 60 70 80 Naxos Avocet-YrA AxN-39_res AxN-39_sus PM severity (%) Evaluation of NILs for 1AS QTL First score 10.07.2016 Second score 20.07.2016 Fig. 3. Powdery mildew severities of near-isogenic lines for the 1AS QTL along with the parental lines Naxos and Avocet-YrA. Data from hillplot trial at Vollebekk in 2016. gwm33 0.0 BS00022701_51 BW_c6558-234 2.9 AX-94493792 4.9 BS00022977_51 5.2 AX-95154988 BW_c1265_607 AX-95089648 BS00100287_51 AX-94910059 wKu_c5756_10191339 6.0 AX-94629244 6.5 Ex_c55677_217 11.2 AX-94615199 11.6 QTL area Fig. 4. Linkage map of the 1AS QTL area based on 35K and 90K markers genotyped with the KASP system on 318 segregating lines from heterozygous plants of RIL AxN-39. Development of a fine-mapping population Heterozygous plants from the segregating F 6 family AxN- 39 were selfed to produce a fine-mapping population of 318 segregating lines for the QTL in a uniform genetic background. These were genotyped with KASP markers for the target QTL area developed from the Illumnia 90K and Affymetrix 35K SNP chips. The resulting linkage map is shown in Fig. 4. Individual plants representing recombination events within the QTL area have been selfed to produce sets of near-isogenic lines for the different breakpoints. These will be tested for powdery mildew resistance in the upcoming 2017 season to further refine the QTL area. References Lu Q, Bjørnstad Å, Ren Y, Asad M, Xia X, Chen X, Ji F, Shi J, Lillemo M (2012) Partial resistance to powdery mildew in German spring wheat ‘Naxos’ is based on multiple genes with stable effects in diverse environments. Theor Appl Genet 125:297-309 Windju SS, Malla K, Belova T, Wilson RC, Dieseth JA, Alsheikh MK, Lillemo M (2017) Mapping and validation of powdery mildew resistance loci from spring wheat cv. Naxos with SNP markers. Mol Breeding (accepted)
Transcript of Fine mapping and validation of a major locus for race non ... · RIL (left) and the resistance...
Near-isogenic lines for the 1AS QTLThe genotyping of the Avocet x Naxos RIL populationidentified one F6 family (AxN-39) with heterozygousgenotype calls for markers in the QTL area. Near-isogeniclines(NILS)were produced fromheterozygous segregantsfor validation of the phenotypes in the field. As shown inFig. 3, the QTL contributed to more than a 50% reductionin powdery mildew severity in this near-isogenicbackground. We then decided to develop a fine-mappingpopulation based on this segregating F6 family in orderto mendelize the QTL.
IntroductionPowdery mildew, caused by Blumeria graminis f. sp. triticiis a major wheat disease in maritime and temperateclimates. It can cause yield losses up to 40% if notproperly controlled. Resistance breeding is considered amore sustainable and economic alternative to chemicaldisease control with fungicides. While race-specificresistance often is of short durability, long-lastingresistance can be achieved by combining several genesfor partial, and race non-specific resistance.The German spring wheat cv. ‘Naxos’ shows a high levelof partial resistance to powdery mildew in the field(Fig. 1), and in a previous study we identified a majorQTL on 1AS with resistance from Naxos in theSHA3/CBRD x Naxos recombined inbred line (RIL)population based on QTL mapping with SSR and DArTmarkers (Lu et al. 2012).Validation with SNP markersRecently, we further refined the linkage maps withinclusion of SNP markers from the Illumina 90K wheatchip and narrowed down the QTL area. For validation,QTL mapping with 90K SNP markers was also done inthe SORU#1 x Naxos population. Again, the 1AS QTL fromNaxos was identified as a major determinant of powderymildew resistance, explaining from 10 to 19% of thephenotypic variance in the field. The colinearity ofcommon SNP markers confirmed that the QTL was thesame in the two populations (Fig. 2, Windju et al. 2017).A third RIL population, Avocet x Naxos was phenotypedin the field and genotyped with KASP markers developedfrom the most significant 90K SNP markers on 1AS inSORU#1 x Naxos. The QTL was validated also in thispopulation, and explained up to 10% of the phenotypicvariance (data not shown).
AcknowledgmentsThis work has been funded through research grants fromthe Research Council of Norway. We are thankful to fieldtechnicians Cecilie Yri and Yalew Tarkegne for help withthe field trials and lab engineer Anne Guri Marøy for themarker genotyping.
Susanne S. Windju1,2, Keshav B. Malla1,2,3, Tatiana Belova1, Robert C. Wilson3, Jon Arne Dieseth2, Muath K. Alsheikh1,2, Morten Lillemo1
1Department of Plant Sciences, Norwegian University of Life Sciences, Post Box 5003, NO-1432 Ås, Norway; e-mail: [email protected] AS, Hommelstadvegen 60, NO-2322 Ridabu, Norway3Faculty of Education and Natural Sciences, Inland Norway University of Applied Sciences, Post Box 400, NO-2418 Elverum, Norway
Fine mapping and validation of a major locus for race non-specific partial resistance to powdery mildew on chromosome
arm 1AS in the German spring wheat cv. ‘Naxos’
Fig. 2. Alignment of the linkage maps and corresponding LOD curves from the QTL mapping of powdery mildew resistance on1AS in the two mapping populations SHA3/CBRD x Naxos and SORU#1 x Naxos.
Fig. 1. Powdery mildew symptoms of a highly susceptible RIL (left) and the resistance source Naxos (right) in hillplots.
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Evaluation of NILs for 1AS QTLFirst score 10.07.2016 Second score 20.07.2016
Fig. 3. Powdery mildew severities of near-isogenic lines for the 1AS QTL along with the parental lines Naxos and Avocet-YrA. Data from hillplot trial at Vollebekk in 2016.
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Fig. 4. Linkage map of the 1AS QTL area based on 35K and 90K markers genotyped with the KASP system on 318 segregating lines from heterozygous plants of RIL AxN-39.
Development of a fine-mapping populationHeterozygous plants from the segregating F6 family AxN-39 were selfed to produce a fine-mapping population of318 segregating lines for the QTL in a uniform geneticbackground. These were genotyped with KASP markersfor the target QTL area developed from the Illumnia 90Kand Affymetrix 35K SNP chips. The resulting linkage mapis shown in Fig. 4. Individual plants representingrecombination events within the QTL area have beenselfed to produce sets of near-isogenic lines for thedifferent breakpoints. These will be tested for powderymildew resistance in the upcoming 2017 season tofurther refine the QTL area.
ReferencesLu Q, Bjørnstad Å, Ren Y, Asad M, Xia X, Chen X, Ji F, Shi J, Lillemo M(2012) Partial resistance to powdery mildew in German springwheat ‘Naxos’ is based on multiple genes with stable effects indiverse environments. Theor Appl Genet 125:297-309Windju SS, Malla K, Belova T, Wilson RC, Dieseth JA, Alsheikh MK,Lillemo M (2017) Mapping and validation of powdery mildewresistance loci from spring wheat cv. Naxos with SNP markers. MolBreeding (accepted)
