Epistatic determinism of durum wheat resistance to the wheat spindle streak mosaic virus

Abstract

Key message The resistance of durum wheat to the Wheat spindle streak mosaic virus (WSSMV) is controlled by two main QTLs on chromosomes 7A and 7B, with a huge epistatic effect. Abstract Wheat spindle streak mosaic virus (WSSMV) is a major disease of durum wheat in Europe and North America. Breeding WSSMV-resistant cultivars is currently the only way to control the virus since no treatment is available. This paper reports studies of the inheritance of WSSMV resistance using two related durum wheat populations obtained by crossing two elite cultivars with a WSSMV-resistant emmer cultivar. In 2012 and 2015, 354 recombinant inbred lines (RIL) were phenotyped using visual notations, ELISA and qPCR and genotyped using locus targeted capture and sequencing. This allowed us to build a consensus genetic map of 8568 markers and identify three chromosomal regions involved in WSSMV resistance. Two major regions (located on chromosomes 7A and 7B) jointly explain, on the basis of epistatic interactions, up to 43% of the phenotypic variation. Flanking sequences of our genetic markers are provided to facilitate future marker-assisted selection of WSSMV-resistant cultivars.Electronic supplementary materialThe online version of this article (doi:10.1007/s00122-017-2904-6) contains supplementary material, which is available to authorized users.

Genome‐wide association analysis of resistance to wheat spindle streak mosaic virus in bread wheat

“…In durum wheat, only the cultivar Soldur has been reported as resistant to WSSMV and is broadly used as a source of resistance by breeders (Holtz et al ., ). Unfortunately, the QTL found in the present study was located on the D genome and therefore cannot be used to improve WSSMV resistance in durum wheat by classical breeding techniques, and more complex methods would be required in order to introgress this bread wheat QTL into the durum wheat genome.…”

“…The linkage disequilibrium in this chromosomal region was found to be surprisingly high in this panel of registered cultivars, thus showing that recombination within this region is expected to be very low. Given all the possible practical difficulties in phenotyping WSSMV resistance in naturally contaminated fields (Holtz et al ., ), an error in the phenotype cannot be excluded.…”

“…As both viruses are carried by the same family of vector and share around 70% homology in RNA sequence, they may share a common resistance mechanism. Recently, Holtz et al (2017) identified two major QTLs located on chromosomes 7A and 7B and one minor QTL on chromosome 2A associated to WSSMV resistance in two populations of recombinant inbred lines obtained by crossing two elite durum wheat cultivars with a WSSMV-resistant emmer cultivar (T. turgidum dicoccoides). They also reported epistatic interactions between the two QTLs on chromosomes 7A and 7B.…”

“…However, no durum wheat cultivars currently registered in France are resistant to WSSMV. The cultivar Soldur was identified as resistant to WSSMV (Holtz et al ., ) but is no longer registered in the official catalogue of species and varieties of cultivated crops in France (https://www.geves.fr/catalogue-france/). To avoid significant losses, farmers must grow resistant bread wheat cultivars instead of durum wheat on contaminated fields.…”