Phenolic acid changes during Orobanche parasitism on faba bean and some other hosts
AbstractThe present work is intended to provide further information on broomrape parasitism based on phenolic acid changes in either the host plant(s) or in each of the host and the parasite in the host-parasite system. Detection of phenolic acids was carried out using high performance liquid chromatography (HPLC) in the host and broomrape tissues. This was carried out first in shoots and roots of faba bean before (33-day-old) and after (65-, 74-, 80-day-old) broomrape infestation. Shoots and roots of faba bean and other prospective hosts (tomato and eggplant), during parasitism, at full juvenility of broomrape just before blooming, were also scanned. Chlorogenic acid occurred predominantly as phenolic compounds in shoots and roots of the host plants. The occurrence of chlorogenic acid was unique to the roots of the faba bean plant at different stages of development of the parasite, as well as in the roots of other infected hosts. In shoots of the infected hosts, inconsistent variations were observed in the ratios of caffeic, ferulic, as well as ortho-, para- and metacoumaric acids. Detection of phenolic acids in stems of broomrape, parasitizing faba bean, indicated the occurrence of chlorogenic acid at different stages of growth of the parasite. In addition to chlorogenic acid, the results also revealed the existence of M-coumaric acid at the emergence stage, P-coumaric and ferulic acids at early blooming and caffeic acid at the late blooming stage. Qualitative changes were also observed in broomrape tissue according to the type of host (faba bean, chamomile, eggplant, and cabbage). On the other hand, chlorogenic acid was the only phenolic compound detected in the corm-like tubercle tissue of broomrape with different hosts. The possible interference of phenolic acids in tissues of both the hosts and broomrape was discussed.
KEY WORDS: Broomrape parasitism, Phenolic acids, HPLC, faba bean.
Egyptian Journal of Biology Vol.4 2002: 37-44