PARENT SESSION
Oral Session # 33: Pathogens, Toxins, and Disease II: Plants.
Presiding: A Davelos
Tuesday, August 5. 1:30 PM to 5:00 PM, SITCC Meeting Room 201.
The role of fungal pathogens on seed mass variation and seed production in 3 species of Hydrophyllum.
Marr, Deborah*,1, 1 Indiana University South Bend, South Bend, IN, USA
ABSTRACT- Many plant species exhibit little variation in seed size, however there are some species in which seed size varies 10 fold or more. The persistence of this variation is intriguing because both empirical and theoretical studies predict that seed size should be less variable compared to other reproductive traits because larger seeds generally have higher fitness within species. I studied seed mass variation in three species of Hydrophyllum, H. appendiculatum, H. canadense, and H. virginianum to better understand the range of natural variation found in these closely related species. These species coexist as understory herbs in deciduous forests throughout the midwestern United States. The range in seed mass produced by individual maternal plants varied widely among the three species. The greatest amount of seed mass variation was observed in H. appendiculatum and H. canadense; over 30% of maternal plants in both species produced seeds that varied at least 8 fold in size. However, fewer than 7% of the H. virginianum maternal plants produced seeds that varied 7 fold in size. Both H. appendiculatum and H. canadense, were frequently infected by fungal pathogens (Fusarium sp. and Rhizoctonia sp.) that caused stems and inflorescences to wilt. In contrast, wilting was not observed in H. virginianum in the study sites. To test whether seed production and seed mass were affected by the disease status of the individual in H. canadense, seeds were collected from healthy and diseased individuals that were hand-pollinated in the field with supplemental pollen. Diseased individuals produced significantly fewer fruits, but no difference in seed mass variation between healthy and diseased maternal plants was found. Further studies of all three species in which maternal environment is controlled will help determine whether pathogens that cause wilt contribute significantly to the unusual seed size variation in Hydrophyllum.
Key words: plant-fungal interactions, Hydrophyllum , seed size variation