Crown rust caused by the fungus Puccinia coronata f. sp.
lolii is probably the most serious disease of perennial
ryegrass (Lolium perenne L.). Breeding for resistance to
crown rust is a major component of most perennial ryegrass improvement
programs. This paper reviews the genetic basis of resistance to crown rust in
perennial ryegrass, existing breeding strategies and their progress, and
genetic variation in pathogen populations. Resistance to crown rust in
perennial ryegrass appears to be controlled by both major and minor genes.
Breeding for resistance to crown rust has traditionally been approached from a
quantitative perspective (polygenic system), and phenotypic recurrent
selection is by far the most commonly used method of selection. There appears
to be considerable variation in the pathogen population which may impact on
breeding progress. Owing to the present lack of information on the
host–pathogen interaction system of this economically important disease,
a basic model to study the
L. perenne–P. coronata f.
sp. lolii interaction system is presented. Its
application in a breeding program is discussed.