VAM association in the shrub Myrica cerifera on a Virginia, USA barrier island

Abstract

A combined laboratory and field study examined the potential for a symbiotic association between the actinorhizal shrub Myrica cerifera and vesicular arbuscular mycorrhizal (VAM) fungi on a Virginia barrier island. M. cerifera seedlings and two test species, Zea mays and Strophostyles umbellata, were grown in an environmental chamber on soils collected from four sites differing in soil age (< 5 to over 130 years), salinity (1–35 μg/g total soil chloride), and edaphic characteristics. Seedling root infection was significantly lower for all three species in the youngest soils from the beach where salinity was highest. Stained M. cerifera roots revealed all the components for a functional VAM association; however, there were significantly fewer arbuscules and vesicles relative to the test species. Among field-collected M. cerifera, infection was not detected in mature shrubs from the bay side of the island, where M. cerifera thickets were in a state of degeneration. Infection was highest in soils from the young, developing thickets, and in the most stable thickets of the island interior. Despite the dynamic nature of the barrier island environment, VAM associations with M. cerifera appear to be present, especially in seedlings and developing shrub thickets.