Sequence tagged site markers to rsp1, rsp2, and rsp3 genes for resistance to septoria speckled leaf blotch in barley

Determining the order of resistance genes against Stagonospora nodorum blotch, Fusarium head blight and stem rust on wheat chromosome arm 3BS

BACKGROUND

Stagonospora nodorum blotch (SNB), Fusarium head blight (FHB) and stem rust (SR), caused by the fungi Parastagonospora (synonym Stagonospora) nodorum, Fusarium graminearum and Puccinia graminis, respectively, significantly reduce yield and quality of wheat. Three resistance factors, QSng.sfr-3BS, Fhb1 and Sr2, conferring resistance, respectively, to SNB, FHB and SR, each from a unique donor line, were mapped previously to the short arm of wheat chromosome 3B. Based on published reports, our hypothesis was that Sr2 is the most distal, Fhb1 the most proximal and QSng.sfr-3BS is in between Sr2 and Fhb1 on wheat chromosome arm 3BS.

RESULTS

To test this hypothesis, 1600 F2 plants from crosses between parental lines Arina, Alsen and Ocoroni86, conferring resistance genes QSng.sfr-3BS, Fhb1 and Sr2, respectively, were genotyped and phenotyped for SNB along with the parental lines. Five closely linked single-nucleotide polymorphism (SNP) markers were used to make the genetic map and determine the gene order.

CONCLUSIONS

The results indicate that QSng.sfr-3BS is located between the other two resistance genes on chromosome 3BS. Knowing the positional order of these resistance genes will aid in developing a wheat line with all three genes in coupling, which has the potential to provide broad-spectrum resistance preventing grain yield and quality losses.

Novel septoria speckled leaf blotch resistance loci in a barley doubled-haploid population

The genetics of resistance to Septoria speckled leaf blotch (SSLB), caused by Septoria passerinii, was studied in the Leger × CIho9831 barley doubled-haploid population. The 140 lines in the population segregated as 102 resistant and 38 susceptible, approximating a 3:1 ratio. A recombination map was developed using diversity arrays technology and other molecular markers. Quantitative trait locus (QTL) analysis demonstrated that resistance is primarily conferred either by having the CIho9831 allele at a QTL on 6HS or by having the CIho9831 allele at both of two QTLs on 3H and 2HL. In addition, ≈1/16 of the lines were resistant for unidentified reasons. This model predicts a resistant/susceptible ratio of 11:5, which fits the phenotypic observations. Minor QTLs were detected on 2HS and 1H. DNA sequences of linked markers suggest that the 6HS, 3H, and 2HS QTLs are part of resistance gene clusters and that the 6HS and 3H QTLs share homology. The 6HS QTL is identical to or closely linked to the SSLB resistance locus Rsp4 and the 1H QTL to the Rsp2 or Rsp3 locus. The 3H and 2HS QTLs are unique and offer new opportunities for pyramiding resistance genes through marker-assisted breeding for resistance to S. passerinii.

A novel QTL for Septoria speckled leaf blotch resistance in barley (Hordeum vulgare L.) accession PI 643302 by whole-genome QTL mapping

Septoria speckled leaf blotch (SSLB), caused by Septoria passerinii, is one of the most important foliar diseases of barley (Hordeum vulgare L.) in North America. The primary problem caused by this disease is substantial yield loss. The objective of this study was to determine the chromosomal location of SSLB resistance genes in the barley accession PI 643302. A recombinant inbred line population was developed from the cross Zhenongda 7/PI 643302. PI 643302 is resistant while Zhenongda 7 is susceptible to SSLB. The population was phenotyped for SSLB resistance in five experiments in the greenhouse. A linkage map comprising 113 molecular markers was constructed and simplified composite interval mapping was performed. Two QTLs, designated QrSp-1H and QrSP-2H, were found. QrSp-1H was found on the short arm of chromosome 1H (1HS) in all five experiments and showed a large effect against SSLB. Based on the location of QrSp-1H, it is likely the SSLB resistance gene Rsp2. The QTL QrSp-2H mapped to the distal region on the long arm of chromosome 2H (2HL), had a smaller effect than QrSp-1H, and was also detected consistently in all five experiments. A QTL for SSLB resistance in the same region on chromosome 2H has not been reported previously in either cultivated or wild barley; thus, QrSp-2H is a new QTL for SSLB resistance in barley.

Molecular mapping of rsp1, rsp2, and rsp3 genes conferring resistance to septoria speckled leaf blotch in barley

ABSTRACT Septoria speckled leaf blotch (SSLB) caused by Septoria passerinii is a common disease in barley. SSLB resistance genes Rsp1, Rsp2, and Rsp3 have previously been identified in the United States Department of Agriculture National Small Grains collection accessions CIho 14300, CIho 4780, and CIho 10644, respectively. Populations of 100 to 120 F(2) individuals were evaluated for SSLB resistance in the greenhouse. Inheritance was evaluated in F(2:3)-derived families in the field. Partial molecular maps for three Rsp genes were constructed on F(2) and F(2:3) families derived from crosses between Robust and the resistant accessions CIho 14300, CIho 4780, and CIho 10644. The resistant locus Rsp1 was mapped to the short arm of chromosome 3H with two flanking diversity arrays technology (DArT) markers, bPb-6978 (8.9 cM) and bPb-9945 (16.3 cM), and two random amplified polymorphic DNA (RAPD) markers, OPC2(441R) (3.0 cM) and UBC285(158R) (4.3 cM). The genes Rsp2 and Rsp3 were positioned on the short arm of barley chromosome 1H with two restriction fragment length polymorphism (RFLP), six DArT, and three RAPD markers. An RFLP marker, MWG938, and an RAPD marker, OPAH5(545C), were tightly associated with Rsp2 at a distance of 0 cM. Five DArT markers spanning the short arm of 1H surrounded Rsp3 at a distance of 2.3 and 5.8 cM, while two RAPD markers-OPBA12(314C) (2.4 cM) in coupling and OPB17(451R) (3.5 cM) in repulsion-flanked Rsp3. Molecular marker data associated with Rsp2 and Rsp3 indicated that the two genes are closely linked on chromosome 1HS. A total of 17 of 154 simple sequence repeats (SSRs) tested were associated with Rsp genes on chromosome 1H and 3H, and they were also integrated into genetic linkage maps of the three F(2) Robust populations. Knowledge about the map position of Rsp genes on barley chromosomes will be useful for breeding for SSLB resistance in barley and eventual gene cloning.