LAUSR

Orobanche cumana Wallr. is an important new problem for sunflower crop in Tunisia. Little information is available on the behavior of sunflower to O. cumana infestation in this region. Research activities are focusing on screening some sunflower accessions in order to identify resistant ones and to develop other cultural and biological methods to use them in integrated way to reduce the impact of this parasite. For this purpose, field natural infestation and artificial inoculation in pots and Petri dishes evaluations were conducted using eleven sunflower accessions out of them 4 introduced lines were known by their resistance to O. cumana used as reference. In infested field, three of the reference lines (TL12, TL15 and TL16) did not show any emerged broomrape shoot and the values of their major agro-morphological parameters were not affected by parasitism. Results of pots and Petri dishes experiments confirmed the field testing. In the resistant lines, the stems dry weight, the number and weight of sunflower seeds were not significantly reduced under infestation contrarily to the others accessions. The resistance of these lines is characterized by reduced germination percentage of Orobanche seeds and low attachments/tubercles number of the parasite. O. cumana infection do not influence seed oil content in resistant lines contrarily to susceptible accessions. Nevertheless, no relationship was found between fatty acids composition and resistance to broomrape infestation. These results would be useful for improving resistance of sunflower against broomrape.‎