PLOIDY-SPECIFIC INTERACTIONS OF THREE HOST PLANTS WITH ARBUSCULAR MYCORRHIZAL FUNGI: DOES GENOME COPY NUMBER MATTER?

Premise of the study : Polyploidy has been shown to affect different plant traits and modulate interactions between plants and other organisms, such as pollinators and herbivores. However, no information is available on whether it can also shape the functioning of mycorrhizal symbiosis. Methods : The mycorrhizal growth response was assessed for three angiosperms with intraspecific ploidy variation. Different cytotypes of Aster amellus, Campanula gentilis, and Pimpinella saxifraga were either left uninoculated or were inoculated with arbuscular mycorrhizal (AM) fungi in a pot experiment. After 3 mo of cultivation in a greenhouse, plant growth, phosphorus concentration in the shoot biomass, and development of the AM symbiosis were evaluated. Key results : No significant ploidy-specific differences in AM development were recorded. The inoculation led to consistently greater phosphorus uptake; however, the effect on plant growth differed considerably among plant species, populations, ploidy levels, and AM species. A salient ploidy-specific response was observed in A. amellus. Whereas diploid plants benefited from AM inoculation, the hexaploids consistently showed negative or no-growth responses (depending on the AM species). In contrast to A. amellus, no interactions between inoculation and ploidy were observed in C. gentilis and P. saxifraga. Conclusions : The first evidence is provided of a ploidy-specific response of a mycotrophic plant to AM fungi. Our results demonstrate the complexity of interaction between plants and associated AM fungi, with the ploidy level of the host plant being one component that may modulate the functioning of the symbiosis.