Pathogenicity Spectra And Screening For Resistance In Barley Against Tunisian Pyrenophora Teres F. Teres

This work aimed to determine patterns of pathogenicity in Pyrenophora teres f. teres and to identify potentially effective resistance
sources that could be used as breeding material to control net blotch in
Tunisia. Extensive pathogenic variability was detected in 85 isolates of
P. teres causing net blotch of barley in Tunisia. Based on unweighted
pair-group method with arithmetic averaging clustering and mean
disease rating scores, three distinct virulence groups were identified.
The isolates were classified into 23 pathotypes. Pathogenic variability
within the groups was higher than that between the groups, a finding
that can guide a rational choice of isolates for screening lines as part of
a breeding program. Conversely, studying the relationship between
geographic and pathotypic structure allowed us to detect a significant
isolation by distance pattern, suggesting a regular and gradual dispersal
of the pathogen over this spatial scale. Using specific resistance properties of individual barley genotypes as virulence markers, all the differential barley genotypes were shown to be distinct, and no single
source of resistance was totally effective against all isolates.