As two ubiquitous and important components in terrestrial ecosystems, parasitic plants and arbuscular mycorrhizal (AM) fungi have been extensively studied in the past, but in most cases separately. Recent findings suggest that plant parasitism and AM associations have some interesting parallels and may be modulated bysimilar mechanisms. Despite the small but increasing number of efforts to test the influence of host AM status on growth performance of parasitic plants, no investigations have tested the direct interactions between parasitic plants and AM fungi, partially due to the fact that most parasitic plants do NOT form mycorrhizal associations.

Using a facultative root hemiparasite (Pedicularis tricolor Hand.-Mazz.) with a potential to form AM associations, researchers from Kunming Institute of Botany, Chinese Academy of Sciences and University of Adelaideshow that inoculation with some AM fungi strongly suppresses the initiation of haustoria, the parasite-specific structures exclusively responsible for host attachment and nutrient transfer from a host to a parasitic plant. The significant role of AM fungi in haustorium initiation of parasitic plants is demonstrated for the first time.

The research was supported by the Natural Science Foundation of China (grant No. 30970288), the Natural Science Foundation of Yunnan Province (grant No. 2009CD114) and the Overseas Training Program of the Chinese Academy of Sciences for LI Airong. The results have been reported in Annals of Botany (Li et al.,2012, 1-6). http://aob.oxfordjournals.org/content/early/2012/02/22/aob.mcs028.short

Effects of arbuscular mycorrhizal (AM) fungal inoculation on haustorium formation in Pedicularis tricolor. Haustoria are visible as swellings on roots, and some examples are shown with tailed arrows. (A) Presence of the host plant (barley) but without AM inoculation. The inset shows two haustoria (H) with a xylem bridge (XB) connecting a root of P. tricolor (PR) to a root of barley (BR). (B) Presence of the host plant (barley) with inoculation of Glomus intraradices. Note the lower density of haustoria compared with (A). The inset shows a haustorium with an XB connecting PR and BR. Colonization of barley by the AM fungus is also shown (AM). (Images by KIB)