The attack of the Orobanche cumana Wallr. and it's influence on a differential sunflower host assortment under Dobrogea conditions.

Broomrape (Orobanche cumana Wallr.) is the most important parasite of the sunflower crops in the South-East of Romania and is especially spread over Constanta, Tulcea, Ialomita, Braila, Buzau and Calarasi counties where this parasite recorded the most severe attacks. In the last years the parasite became more aggressive for the sunflower crops, with a tendency of spreading toward the adiacent zones of this area and to the west of the country. The broomrape's virulence increased significantly in the last two decades due to a short crop rotation and the use of non-resistant sunflower hybrids, causing a loss of yield and oil production. Experiments for testing Orobanche cumana Wallr. infestation were carried out in 2011 in fields with sunflower monoculture at ARDS Valu lui Traian, Constanta county, and also in open fields of Orobanche at ARDS Valu lui Traian to determine seed and oil production in conditions without infestation. We identified races more aggressive than race E, as the hybrid Favorit (race F resistant) showed infestation. We also identified some populations more aggressive than the race G, but these new populations were present with a lower frequency; the attack degree of the hybrid PR64E71 had very low values, without a negative influence on the yield. The yield losses reported for the hybrid Performer (without resistance genes) were up to 19%. Hybrids with genetic resistance to race F (Favorit) and to races more aggressive than race F (PR64E714) can be successfully cultivated in Dobrogea.