S. Salamati et Am. Tronsmo, PATHOGENICITY OF RHYNCHOSPORIUM-SECALIS ISOLATES FROM NORWAY ON 30 CULTIVARS OF BARLEY, Plant Pathology, 46(3), 1997, pp. 416-424
The pathogenic variability of the barley scald fungus, Rhynchosporium
secalis, in central Norway was examined in 1994. The climate in this r
egion is usually cold and wet during the growing season of spring barl
ey. Leaf blotch is prevalent and causes significant yield losses. Fort
y-two isolates of the fungus, from naturally infected spring barley in
four counties, were differentiated into 32 pathotypes by the standard
differential set for R. secalis. All pathotypes were complex and had
virulence for nine to 22 differentials. The cultivar Osiris was resist
ant to all isolates tested. The cultivars C.I.8162, Hudson, Atlas 46 a
nd C.I.3515 were resistant to the majority of the isolates. Several di
fferentials with various resistance genes were susceptible to up to 10
0% of the isolates. Isolates were derived from local cultivars with no
known resistance genes, suggesting that R. secalis populations in cen
tral Norway are characterized by it high degree of seemingly unnecessa
ry pathogenicity. Because of the great variability and complexity of t
he pathotypes, traditional breeding methods using single major genes a
re not likely to be effective in central Norway.