Green tea catechins applied to susceptible hosts inhibit parasitic plant attachment success
Parasitic plants utilize cell wall degrading enzymes (CWDEs) to penetrate their host plant and attach to host vasculature. Inhibition of CWDEs may confer resistance on susceptible hosts, offering a strategy for parasitic plant control. Here, exogenous application of green tea catechins, which inhibit pectin methylesterase (a CWDE), was used to delay parasitic plant attachment. Texas bluebonnet (Lupinus texensis Hook.) was grown with its naturally occurring root hemiparasite, Texas paintbrush (Castilleja indivisa Engelm.). Catechins, fertilizer (ammonium nitrate), or water were added to soil twice weekly. Parasite attachment was detected using Dragendorff reagent. Effects on growth and germination were also assessed. Parasite attachment to the host was prevented by 5 g L–1 of catechins through 20 d and reduced through 36 d after parasite seedling addition. Five grams per liter of catechins delayed germination in Texas bluebonnet but not in Texas paintbrush. To test the effects of CWDE inhibitors on aboveground parasitism, Arabidopsis thaliana (L.) Heynh. seedlings were grown with field dodder (Cuscuta pentagona Engelm.), a promiscuous shoot holoparasite. Ten grams per liter of catechins applied to the A. thaliana shoot surface inhibited field dodder attachment, although prehaustorial development was not affected. Our findings corroborate existing evidence that CWDE inhibition is a critical component of natural resistance to parasitic plants and open a new area of research into the use of exogenous CWDE inhibitors to control parasitic plant attachment.