OROBANCHE CUMANA WALLR. RESISTANCE OF COMMERCIAL SUNFLOWER CULTIVARS GROWN IN ARGENTINA

The parasitic weed Orobanchecumana Wallr. (broomrape) is one of the major limiting factors in worldwide sunflowerproduction. However, it is absent in the centre of origin and in the sunflowercrop areas of America. It has not yet been elucidated if O. cumana naturalization in sunflowerhabitats in Argentina is restricted as a result of either abiotic constraints or resistance in grown commercial cultivars. The aim of the present study was to assess the degree of resistance of commercial sunflowercultivars grown in Argentina to O. cumana. More than 95% of the tested sunflowercultivars were, in general, susceptible to broomrape attack. Although three cultivars were found to evidence an acceptable response to broomrape attack, only one of them showed complete resistance to O. cumana. This disregards genetic resistance of grown cultivars as being the reason for the absence of broomrape in Argentina. In view of this, future studies should focus on other biotic and abiotic factors affecting broomrape growth and development which could be potentially responsible for the absence of O. cumana in Argentina.