Infection by the systemic fungus Epichloë glyceriae and clonal growth of its host grass Glyceria striata

Abstract

Many plant species have the ability to expand laterally through space by clonal growth. Plant pathogens can affect clonal growth characteristics thereby altering the success of host plants within populations and of clonal species within communities. We conducted a greenhouse experiment to determine the effects of the systemic fungal pathogen, Epichloe glyceriae, on clonal growth patterns of its host grass, Glyceria striata. We found that infected and uninfected plants produced similar total biomass and numbers of tillers plus primary stolons per mother ramet. However, biomass allocation to tillering (vegetative growth) vs stolon production (clonal growth) was significantly affected by pathogen infection. Infected plants produced more stolons and clonal growth biomass than uninfected plants while mother ramets of uninfected plants produced more tillers and biomass than infected plants. Stolon architecture of infected and uninfected plants also differed. In two of three populations, infected plants produced stolons with greater biomass and shorter spacer lengths, even though mean stolon lengths were similar for infected and uninfected plants. These results contrast strongly with most other clonal plant-pathogen systems where infected plants are less vigorous and have reduced clonal growth compared to uninfected plants. Greater clonal growth may be an effective mechanism for host genotypes to persist and spread when seed production is prevented, as is the case with castrating pathogens like Epichloe glyceriae.