Factors Affecting Race Prevalence of Mehmpsora lini.

No correlation was found between virulence of races and their prevalence, although races which attacked one or two genes for resistence only constituted more than 71 % of the isolates studied. Differences in race prevalence were not associated with their incubation or latent period. Uredospore germination of races differing in virulence indicated that a race of narrow virulence and wide prevalence germinated better over a wider range of temperature than races of higher virulence and showed better germ tube elongation at extreme temperatures. These factors may be in part responsible for the wider prevalence of some races. [ABSTRACT FROM AUTHOR]