Mapping and pyramiding of qualitative and quantitative resistance to stripe rust in barley

Abstract

The identification and location of sources of genetic resistance to plant diseases are important contributions to the development of resistant varieties. The combination of different sources and types of resistance in the same genotype should assist in the development of durably resistant varieties. Using a doubled haploid (DH), mapping population of barley, we mapped a qualitative resistance gene ( Rpsx) to barley stripe rust in the accession CI10587 (PI 243183) to the long arm of chromosome 1(7H). We combined the Rpsx gene, through a series of crosses, with three mapped and validated barley stripe rust resistance QTL alleles located on chromosomes 4(4H) (QTL4), 5(1H) (QTL5), and 7(5H) (QTL7). Three different barley DH populations were developed from these crosses, two combining Rpsx with QTL4 and QTL7, and the third combining Rpsx with QTL5. Disease severity testing in four environments and QTL mapping analyses confirmed the effects and locations of Rpsx, QTL4, and QTL5, thereby validating the original estimates of QTL location and effect. QTL alleles on chromosomes 4(4H) and 5(1H) were effective in decreasing disease severity in the absence of the resistance allele at Rpsx. Quantitative resistance effects were mainly additive, although magnitude interactions were detected. Our results indicate that combining qualitative and quantitative resistance in the same genotype is feasible. However, the durability of such resistance pyramids will require challenge from virulent isolates, which currently are not reported in North America.

Marker-assisted selection: an approach for precision plant breeding in the twenty-first century

“…The incorporation of quantitative resistance controlled by QTLs offers another promising strategy to develop durable disease resistance. Castro et al (2003) referred to quantitative resistance as an insurance policy in case of the breakdown of qualitative resistance. A notable example of the combination of quantitative resistance was the pyramiding of a single stripe rust gene and two QTLs (Castro et al 2003).…”

Validation of rice blast resistance genes in barley using a QTL mapping population and near-isolines

“…BCD47 is a two-rowed, spring growth habit DH line, developed via marker-assisted selection for alleles conferring resistance to barley stripe rust (incited by Puccinia striiformis f. sp. hordei) at QTL on chromosome 4H and 5H (Castro et al 2003). Baronesse is a two-rowed, spring growth habit cultivar developed by Nordsaat Saatzucht GmbH and released in 1989 in Germany.…”

“…Briefly, the BSR resistance QTL alleles on chromosomes 4H and 5H trace to BCD47 and the QTL allele on chromosome 1H comes from BCD12 (a sister line of BCD47). The MAS derivation of BCD12 and BCD 47 is described in detail by Castro et al (2003). A "0 QTL" BISON (with susceptible alleles at all resistance loci) was developed from the same germplasm base as the other BISON lines using MAS.…”

“…A "0 QTL" BISON (with susceptible alleles at all resistance loci) was developed from the same germplasm base as the other BISON lines using MAS. D3-6/B23 was the source of the qualitative resistance gene on 7H (Castro et al 2003). Low density forward and background MAS in the iBISON and BISON were performed using an array of marker types, principally SSRs.…”

Quelles perspectives pour la lutte génétique vis-à-vis du mildiou du tournesol ?

“…Castro et al [36] ont démontré qu'il était possible d'associer résistance majeure et résistance partielle dans le cas de la rouille de l'orge. L'une des principales difficultés rencontrées dans ce type de combinaison est le fait que la présence d'un ou de plusieurs gènes majeurs masque la résistance partielle.…”