International Symposium on Cereal Leaf Blights 2019 | University College Dublin, Ireland | 22-24 May 2019

Pyrenophora tritici repentis populations in Tunisia do not fit the known race system

Sana Kamel
Instituite National Agronomique de Tunisie

Mejda Cherif
Instituite National Agronomique de Tunisie

Therese Despins
Lethbridge Research and Development Centre, Agriculture and Agri-Food Canada

Reem Aboukhaddour*
Lethbridge Research and Development Centre, Agriculture and Agri-Foood Canada

Poster Presentation
Cultural Management, Fungicide Resistance and Epidemiology

Atrium, UCD O'Brien centre for Science
Poster 21

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Tan spot, caused by Pyrenophora tritici-repentis (Ptr), is one of the most destructive foliar wheat diseases worldwide. It has become more frequent in Tunisia over the last decade. Infected wheat leaves were collected from durum and bread wheat fields in the northern part of the country where cereal production is concentrated. In this study, the virulence of 74 isolates of Ptr was evaluated on four differential wheat genotypes. Polymerase chain reaction tests with ToxA and ToxB-specific primers were conducted to confirm the presence or absence of these genes in tested pathogen populations. In total, 37 (50%) isolates amplified both ToxA and ToxB genes, and those isolates induced typical symptoms of race 7 where both necrosis and chlorosis developed on corresponding susceptible wheat genotypes. However, the majority of the 35 (47%) isolates which amplified ToxB only, induced necrosis on ‘Glenlea’, and therefore these isolates do not fit the established Ptr race system. Ptr necrosis is typically induced by Ptr ToxA, but here the involvement of other necrosis inducing factor(s) is evident. In conclusion, Ptr pathogenic populations in Tunisia are mainly Ptr ToxB-producers and they do not necessarily follow the established race system, and additional unidentified necrosis factor(s) are most likely involved in pathogenicity.