Sucrose effect on broomrape (Orobanche crenata) development on narbon bean (Vicia narbonensis L.)

The growth and development of broomrapes (Orobanche spp.) fully depends on the nutritional connection established between the parasitic plant and the root of the corresponding host plant. In the present study, narbon bean plants infected with Orobanche crenata were watered with different concentrations of sucrose (0.014, 0.044, 0.088 and 0.146 M) in order to evaluate its effect on the early growth stages of the parasite. The germination of O. crenata seeds decreased with increasing sucrose concentrations and the number of infection attachments of crenata broomrapes decreased significantly when sucrose was present. A parallel experiment was conducted with identical sorbitol concentrations in order to determinate the role of the osmotic potential in the inhibition of the parasite growth. Our results showed that while low sucrose concentrations significantly reduced seed germination in O. crenata, similar concentrations of sorbitol have no significant effect thus indicating that the effect of sucrose is not simply osmotic. Sucrose phytotoxicity was also studied by considering the dry weight of the host plants.