Interaktion zwischen den beiden arbuskulären Mykorrhizapilzen Glomus mosseae und Glomus intraradices unter dem Einfluss des Phosphatgehaltes des Bodens und in Abhängigkeit vom Kohlenhydratstatus der Wirtspflanze Ipomea batatas

Abstract

Phosphate (P) availability in the soil as well as the light supply to the host plant are factors influencing the development of the arbuscular mycorrhizal symbiosis. The aim of the present experiment was to investigate interactions between the two arbuscular mycorrhizal fungi (AMF) Glomus mosseae (GM) and Glomus intraradices (GI) sharing the root system of one plant of sweet potato (Ipomea batatas) under (I) low P availability in the soil and high light supply to the host plant (-P/+L), (II) low P availability in the soil and light deficiency to the host plant (-P/-L) or (III) high P availability in the soil and high light supply to the host plant (+P/+L). Mycorrhizal and nonmycorrhizal plants were grown in a split root system. Among the mycorrhizal treatments, both root parts were either colonized by GI (GI * GI), GM (GM * GM), a 1:1 mixture of both AMF (Mix * Mix) or one part was colonized by GI while the other was colonized by GM (GI * GM). Plants were harvested 40 days after planting. In the (-P/+L) treatment, colonization rates of both fungi did not differ depending on whether they shared the root system with the same or with the other species. In contrast, under (-P/-L) as well as under (+P/+L) conditions, the colonization rates of GM in the (GM*GI) treatment were significantly higher than those of all other treatments while colonization rates of GI were very low in (GI * GI) and (GI * GM). Obviously GM gained profit from a poorer development of GI on the other side of the root system, indicating that the carbohydrate allocation from plant to fungus is regulated by source-sink-relations. Our results demonstrate how changes in the environmental conditions can rapidly alter the composition of the AMF population.