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.