Abstract
O. cumana is an obligatory, non-photosynthetic root parasite. It is believed to have evolved relatively recently from forms of O. cernua parasitizing wild Asteraceae, in particular species of Artemisia, and transferring to cultivated Helianthus annuus (sunflower). O. cumana is thought to be native to Eastern Europe (Russia) and has subsequently spread to most other sunflower growing regions of central and western Europe and Asia. The absence of O. cumana in sunflower growing regions of South America (for example Argentina) is believed to be associated with warmer winter temperatures not suitable for this species, rather than the seeds not being present. O. cumana can cause immense damage to cultivated sunflowers resulting in a significant decrease in yield. Despite resistant sunflower varieties being developed more virulent races of O. cumana have repeatedly evolved, or been selected, to overcome resistance. Thus, in spite of constant breeding efforts, losses continue in established sunflower growing areas and there is potential for it to invade new areas, wherever sunflower is grown.
RESISTANCE TO DISEASES, OBTAINED THROUGH INTERSPECIFIC HYBRIDIZATION / RESISTENCIA A LAS ENFERMEDADES OBTENIDA POR LA HIBRIDIZACION INTERSPECIES / RÉSISTANCE À LA MALADIE OBTENUE PAR HYBRIDATION INTERSPECIES
