Pathogenicity Spectra and Screening for Resistance in Barley Against Tunisian Pyrenophora teres f. teres

Abstract

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.

Virulence of MoroccanPyrenophora teresf.teresRevealed by International Differential Barley Genotypes

“…Harrabi and Kamel (1990) reported that none of the ten barley genotypes used in their study were resistant to 33 Ptt isolates, which originated from the Mediterranean region, though they reported four major virulence groups based on virulence spectrum of these isolates. Later reports on pathogen variability suggested that isolates originating from North African region were highly variable (Douiyssi et al 1998;Bouajila et al 2012). Highly variable Ptt populations were reported by Tuohy et al (2006) in Ireland and Northern Europe, Jonsson et al (1997) in Nordic region, Gupta and Loughman (2001) in Australia, Cromey and Parkes (2003) in New Zealand, and Liu et al (2012) in ND of the USA.…”

“…Resistance to the majority of Ptt isolates is still lacking in the North Africa (Harrabi and Kamel 1990;Douiyssi et al 1998;Yousfi and Ezzahiri 2002;Manninen et al 2006;Jebbouj and El Yousfi 2010;Bouajila et al 2012). Harrabi and Kamel (1990) reported that none of the ten barley genotypes used in their study were resistant to 33 Ptt isolates, which originated from the Mediterranean region, though they reported four major virulence groups based on virulence spectrum of these isolates.…”

Phenotypic and Molecular Diversity of Cochliobolus sativus Populations from Wheat

“…The term "virulence" is defined as the ability of an isolate to cause disease by overcoming a specific host R gene and "pathogenicity" as hoth the specific and nonspecific disease-causing abilities of a pathogen (49). Similarly, the term "pathotype" was used to describe levels of aggressiveness of isolates with a smaller set of differential genotypes for C. sativus (17,23), and Pyrenophora teres f. teres from barley (7,28). Similarly, the term "pathotype" was used to describe levels of aggressiveness of isolates with a smaller set of differential genotypes for C. sativus (17,23), and Pyrenophora teres f. teres from barley (7,28).…”