Comparative Analysis of Disease Resistance Between Ryegrass and Cereal Crops

Perennial ryegrass (Lolium perenne L.) is one of the important forage and turf grasses in temperate zones in the world. Gray leaf spot caused by the fungus Pyricularia oryzae has recently become a serious problem on perennial ryegrass for golf course fairways. The causal agent also causes rice blast disease on rice, as well as foliar diseases on wheat and barley. Crown and stem rust caused by Puccinia spp. are also important for forage- and turf-type perennial ryegrass and seed production. In addition, foliar diseases caused by Bipolaris species, are common and widespread on graminaceous plants. Despite a recent advancement of molecular markers for forage and turf grasses, effective utilization of genetic information available in cereal crops will significantly lead to better understanding of the genetic architecture of disease resistance in ryegrass. Quantitative trait loci (QTL) analysis based on a three-generation interspecific ryegrass population detected a total of 16 QTLs for resistance to the four pathogens. Those QTL were compared with 45 resistance loci for the same or related pathogens previously identified in cereal crops, based on comparative genome analysis using a ryegrass genetic map and a rice physical map. Some pathogen-specific QTLs identified in ryegrass were conserved at corresponding genome regions in cereals but coincidence of QTLs for disease resistance in ryegrass and cereals was not statistically significant at the genome-wide comparison. In conclusion, the conserved synteny of disease resistance loci will facilitate transferring genetic resources for disease resistance between ryegrass and cereals to accommodate breeding needs for developing multiple disease resistance cultivars in ryegrass.