Field study of the interaction between Orobanche crenata Forsk. and some new lines of Vicia faba L. in Egypt

In Egypt, some newly derived lines of faba bean ( Vicia faba L.) as well as Giza 402, all of which had shown a certain resistance against the parasitic weed Orobanche crenata Forsk., were tested in the field. For reasons of comparison, the susceptible cultivars Giza 3 and Reina Blanca were included in this test. Faba bean plants and Orobanche attachments were regularly harvested and examined. The susceptible cultivars completely collapsed before the end of the growing season, whereas others, particularly line 402/294, remained alive until pod formation was completed. It appeared that fewer Orobanche spikes emerged on the new lines and Giza 402. Evidence is given that this was not due to avoidance mechanisms, such as smaller root mass, a deeper root system or lack of germination stimulants. Numbers of Orobanche attachments per unit of lateral root length were found to be low. Hence, it could be concluded that these lines are partially resistant; this resistance must be due to some defence mechanism in their roots. The few Orobanche plants attached grew very fast so that final Orobanche dry weight was similar in resistant and susceptible host plants. Further experiments, including broomrape-free controls, are required to study whether some tolerance mechanism might be involved.