Monday, November 13, 2006 - 8:15 AM

Comparative genetics of disease resistance in turfgrass with cereals.

Geunhwa Jung1, Young-Ki Jo1, Reed Barker2, and Scott Warnke3. (1) Univ. of Wisconsin-Plant Pathology, 1630 Linden Drive; 236 Russell Labs, 1630 Linden Drive; 236 Russell Labs, Madison, WI 53706, United States of America, (2) USDA/ARS, ARS Natl Forage Seed Prod Res Ctr., ARS Natl Forage Seed Prod Res Ctr., Corvallis, OR 97331-7102, United States of America, (3) USDA ARS, 10300 Baltimore Ave., Building 010-A, Beltsville, MD 20705

Perennial ryegrass (Lolium perenne) is one of the most important forage crops in Europe and Australia and also a popular turfgrass in North America.  Improvement of resistance to multiple diseases is desirable for perennial crops like turfgrass that have long rotation cycles.  Quantitative trait loci (QTL) analysis based on a three-generation interspecific ryegrass population was conducted to define partial resistance to four different fungal diseases: leaf spot (Bipolaris sorokiniana), gray leaf spot (Magneporthe grisea), crown rust (Puccinia coronata), and stem rust (Puccinia graminis).  A total of 16 QTLs conferring disease resistance to these four pathogens were mapped on six of seven genetic linkage groups (LG) of ryegrass.  These disease resistance QTLs were compared with disease resistance loci previously identified in cereal crops, using the rice physical map as a reference map.  Most of pathogen-specific QTLs identified in ryegrass also occurred at corresponding positions in cereal crops. One genomic region associated with multiple disease resistances was found on ryegrass LG 4 which has a syntenic relationship with a genomic region of rice chromosome 3 where broad-spectrum resistance loci were found.  Results of this comparative QTL analysis using the integrated map of both ryegrass genetic map and rice physical map indicated the conservation of pathogen-specific partial resistance between ryegrass and cereal crops as well as of broad-spectrum resistance to multiple diseases.  Therefore, genetic information on disease resistance genes identified in rice or other cereal crops can be readily transferred into understudied turfgrass so that breeding for multiple disease resistant cultivars can be greatly facilitated via marker-assisted selection and gene pyramiding approaches.  Turfgrass and forage species may contain ancient disease resistance which can provide a new source of disease resistance genes for cereal crops domesticated for many hundred years.