Potential allelopathic effects of an invasive species Solidago canadensis on the mycorrhizae of native plant species

Effects of alien plant invasion on mycorrhizal colonization of native species is known, but how the invasive species alter the mycorrhizal colonization is not known. We did three experiments to examine whether invasive species affects mycorrhizae by exuding allelochemicals. With the invasive species, Solidago canadensis and three native species: Echinochloa crusgalli, Kummerowia striata and Ageratum conyzoides. An indigenous arbuscular mycorrhizal fungi (AMF) community consisting of five Glomus species (equal number of spore of each species) was constructed. In the first experiment, extracts from rhizome of S. canadensis were added to the monocultures of test plant species that grew under the constructed mycorrhizal community. In the second experiment, S. canadensis were included with each native species under the constructed mycorrhizal community either with or without activated carbon to separate the allelopathic effects from non-allelopathic effects. In the third experiment, native plants were grown in the soil invaded by S. canadensis for one year. The results showed that extracts from rhizomes of S. canadensis significantly inhibited the AMF colonization of three native test plant species. Compared to monoculture, mycorrhizal colonization of native plants decreased, when grown together with S. canadensis. In mixture with S. Canadensis, mycorrhizal colonization of native plants was higher with activated carbon than without activated carbon. S. canadensis altered the indigenous mycorrhizal fungal spore composition and reduced the mycorrhizal colonization of native plants one year after invasion. Thus invasive specie S. canadensis inhibited the AM colonization of native species and changed the indigenous mycorrhizal fungi by exuding allelochemicals.