A four resistance loci pyramiding MAS scheme in barley

The most serious diseases for the barley crop in Southern Europe environments, where mildew and other leaf fungi have a relatively small or not significant effect on yields, are the soil-borne barley yellow mosaic virus (BaYMV), the aphid-borne barley yellow dwarf virus (BYDV) and the seed-borne fungus Pyrenophora graminea (leaf stripe). Developing barley cultivars resistant to the three diseases, while being an urgent objective of barley breeding, in a context of increasing organic farming for cereals, encounters several problems and cultivars resistant to all the former diseases are not yet available. The problems of barley breeding for resistance to BYDV are the availability of sources of resistance, mainly based on semi-dominant Yd2 gene, and the labour-intensive inoculation test made with infected aphids. Availability of resistant cultivars and inoculation test is easier for BaYMV and, in relative terms, also for leaf stripe. Indeed, in normal breeding schemes is quite difficult and anyway expensive to perform all resistance tests on the segregating progenies. For these reasons, it has been developed few years ago a "gene pyramiding" MAS (molecular-assisted selection) scheme to introduce four loci of resistance - two to leaf stripe, and one each to BYDV and BaYMV - into the elite winter barley cultivar Nure. Nure is in fact a highly yielding cultivar, adapted to Southern European environments, but lacking of most important resistances. STS and SSR markers have been adapted to the aim and applied to segregating progenies together with phenotypic selection for agronomic traits. The four loci have been introgressed successfully in couples at homozygosity into F3 families, for the final consolidation of the four into the Nure winter type background.In this work it is reported the molecular-assisted breeding history of the resistance gene pyramiding into this cultivar.