Breeding Barley for Multiple Disease Resistance in the Upper MidwestRegion of the USA

Abstract

The Upper Midwest is one of the largest barley production areas in the USA. In this region, diseases can markedly reduce both the yield and quality of the crop. Molecular and classical breeding techniques are being employed to develop cultivars with resistance to five different diseases in the Minnesota barley improvement program. Stem rust and spot blotch have been successfully controlled for many years through the deployment of the major gene Rpg1 and a major effect QTL, respectively. A sequence characterized amplified region (SCAR) marker developed from the sequence of Rpg1 has made marker-assisted selection (MAS) for stem rust resistance highly effective. The major QTL controlling durable adult plant spot blotch resistance was first identified in the Steptoe/Morex population. This QTL was completely suppressed in the Harrington/Morex and Dicktoo/Morex populations, highlighting the importance of genetic background for the expression of resistance. The onset of Fusarium head blight (FHB) in 1993 led to dramatic changes in the focus of the breeding program. Significant resources have been expended to develop populations for mapping resistance QTL and identify closely linked markers for MAS. This is a difficult challenge because FHB resistance is controlled by many QTL with small effects. Sources of resistance to net blotch and Septoria speckled leaf blotch (SSLB) have been identified in a number of barley accessions. These resistances are simply inherited and are being introgressed into elite lines via phenotypic and MAS. Continued progress toward multiple disease resistance will require efficient phenotypic screening, MAS, and utilization of discoveries in barley genomics to manage numerous resistance genes and desirable gene complexes assembled over decades of breeding.