Effect of temperature on the relationship between Orobanche spp. and carrot (Daucus carota L.)

Orobanche crenata Forsk. and O. aegyptiaca Pars. parasitize carrot (Daucus carota L.) only in specific seasons in Israel. This study describes the relationship between temperature and the sensitivity of carrots to O, crenata and O. aegyptiaca. Field and controlled condition studies have shown that cool temperatures below 18 degreesC are required for the two Orobanche species to parasitize carrot plants. In vitro studies demonstrated that carrots grown under an unfavorable regime (e.g., summer temperatures) have induced seed germination of both Orobanche species, and a substantial numbers of initial attachments were also observed. However, the development of the majority of the attached Orobanche organs ceased. We conclude that both Orobanche species require cool temperatures for effective parasitism on carrot to occur. (C) 2001 Elsevier Science Ltd. All rights reserved.