Abstract
Several strategies have been proposed to control parasitic plants and these include biological control, the use of herbicides, and suicidal germination or trap crops. In the case of sunflower, the most effective solution is genetic resistance. Nevertheless, the use of resistant cultivars is followed by the appearance of new and more virulent races of the parasite that overcome the existing sources of resistance. For this reason, it is necessary to increase our knowledge of the mechanisms involved in the resistant varieties. In this study, the presence of compounds involved in pre-attachment resistance mechanisms in sunflower varieties was analyzed. The production of stimulators of the germination of parasitic plant seeds and the concentration of the haustorial elongation inhibitor, scopoletin, were measured in exudates of resistant and susceptible sunflower varieties. It was found that dehydrocostuslactone and orobanchyl acetate are not involved in the resistance of the sunflower varieties studied. The results demonstrate that costunolide, heliolactone, and scopoletin are related to sunflower resistance. The sunflower varieties studied do not use all available options to fight parasitic plants. This could be one of the reasons that sunflower resistance is rapidly overcome by broomrape.
Highlights
Sunflower (Helianthus annuus L.) is one of the most important crops in many regions of the world, such as Ukraine, Russia, Argentina, and Romania, because it is one of the major sources of vegetable oil [1]
It was found that dehydrocostuslactone and orobanchyl acetate are not involved in the resistance of the sunflower varieties studied
The sesquiterpene lactones (STLs) costunolide and dehydrocostuslactone, and the SLs heliolactone and orobanchyl acetate were identified in all varieties
Summary
Sunflower (Helianthus annuus L.) is one of the most important crops in many regions of the world, such as Ukraine, Russia, Argentina, and Romania, because it is one of the major sources of vegetable oil [1]. Orobanche species are root parasitic plants and holoparasites that depend entirely on the host for their supply of water and nutrients [4]. Their optimum germination temperature is between 15 and 25 ◦C. Most broomrapes are located in the temperate and warm regions of the northern hemisphere, the Mediterranean region and the Middle East. They can be found in a similar climate in Australia, California, and Cuba [5]
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