Host Flower Infection of Silene latifolia by Microbotryum violaceum

Certain fungi can infect host plants and thereby cause sterility of the host. One such fungal parasite, Microbotryum violaceum (commonly known as anther smut), has host specificity to plants of the family Caryophyllaceae. Anther smut takes over the host reproductive system by inhibiting sex-organ development in flowers, and the plant produces fungal spores in place of its normal reproductive structures. Spores can then be spread to nearby hosts through wind and insect pollinators. This experiment focuses on Silene latifolia plant populations growing near Zagreb, Croatia. Our research tests for phenotypic differences between infected and healthy flowers. To do this, we measured the size of healthy and infected flowers of both sexes. Additionally, we observed the proportion of infected flowers over time on individuals to uncover temporal trends of the smut infection. We found that all flower parts, regardless of plant sex, are significantly smaller in smut-infected flowers. After observing proportions of infected flowers, we found that the ratio of infected to healthy flowers increased over time. Our findings suggest that smut infection of S. latifolia causes changes in plant energy allocation. We propose that the smaller flower size could be the result of increased energy needed for M. violaceum spore production. This hypothesis could be tested with additional research. The increasing proportion of smutty flowers on an infected individual over time is likely caused by the spread of the infection throughout the plant.