PATHOGENIC VARIABILITY OF PHYTOPHTHORA NICOTIANAE ON PEPPER IN TUNISIA
M. Saadoun, M.B. Allagui
Pathogenic variability of 15 different isolates of Phytophthora nicotianae was determined following inoculation of six pepper (Capsicum annuum L.) varieties at the seedling stage. Cvs Beldi, Baker and D’hirat were susceptible, whilst Baklouti and Nabeul II showed a significant interaction variety x isolate, and the Mexican landrace Criollo de Morales 334 was strongly resistant to all isolates. Results clustered the 15 P. nicotianae isolates into four pathogenic groups. The first included the weakly virulent isolate Pnt317, which was able to attack only cvs Beldi and Baker. Isolate Pnt341 constituted the second group which was more pathogenic than the first, being able to attack also cv. D’hirat. Isolates Pnt314, Pnt323 and Pnt326 formed the third group, characterized by a high pathogenic power on cvs Beldi, Baker, D’hirat and Nabeul II. The fourth group, which comprised the widest isolate range was the most pathogenic since it attacked all the local varieties but not CM 334. To improve varietal resistance to P. nicotianae, pepper breeders in the Mediterranean region should take into account the pathogenic variability determined in this study.