Exploring the tritrophic interactions between Araujia hortorum, Puccinia araujiae, and a mycoparasitic Cladosporium: implications for the biological control of moth plant.

Tritrophic interactions involving host plants, fungal pathogens and mycoparasites play an important role in the dynamics of natural ecosystems. In this work, we investigate the impact of the rust fungus Puccinia araujiae on the growth of Araujia hortorum plants in the presence/absence of a mycoparasitic Cladosporium species identified here as Cladosporium sphaerospermum, supported by both morphological and molecular studies. The capacity of the latter to grow and reproduce at the expense of teliospores of the rust was confirmed through microscopic observations. P. araujiae is added to the list of hosts of C. sphaerospermum. An experiment was carried out to assess the impact of rust infection on host plant biomass and whether C. sphaerospermum affected the outcome of the interaction. Plants were subjected to three treatments: inoculation with the rust alone, inoculation with both the rust and the mycoparasite, and uninoculated controls. Rust-infected plants (both with and without the mycoparasite) exhibited 50-60 % reductions in biomass, primarily in root tissues, with premature senescence and leaf abscission contributing to overall decline. However, rust-infected plants in the absence of the mycoparasite produced 10 % less biomass than those in the treatment where it was present, showing that C. sphaerospermum is capable of exerting a detrimental effect on the rust which in turn reflects on a better performance of the plant host. It is argued that this fact does not preclude the potential of P. araujiae as a biological control agent.