PARENT SESSION
Oral Session # 53: Herbivory IV: Communities, Populations, and Genetics.
Presiding: JA Rudgers
Wednesday, August 6. 1:30 PM to 5:00 PM, SITCC Meeting Room 103.
Herbivores, herbivore-vectored disease, and inbreeding in Cucurbita pepo ssp texana.
Winsor, James *,1, Leyshon, Bradley2, Travers, Steven1, Stephenson, Andrew1, 1 The Pennsylvania State University-Altoona, Altoona, PA, USA2 The Pennsylvania State University-University Park, University Park, PA, USA
ABSTRACT- Preliminary studies indicated that inbred plants experience higher populations of herbivores and greater herbivore damage than do outbred plants. We wished to determine the relationship among the level of inbreeding, incidence of herbivore infestation, herbivore damage, and infection by herbivore-vectored disease. A garden experiment was conducted using inbred and outbred plants in which herbivores were excluded from half the plants (by spraying with a commercial pyrethroid insectide) while the remaining plants were exposed to herbivores (unsprayed). We recorded presence of herbivores, incidence of herbivore-vectored disease (e.g., cucumber mosaic virus, bacterial wilt), and a suite of measures of male and female plant fitness. The spraying treatment significantly reduced aphid infestation (p<0.001), damage by diabroticite beetles (p<0.001), and infection by mosaic viruses (p<0.001) in both inbred and outbred plants. Inbred plants were more likely to sustain beetle damage (p<0.05) but were no more likely to be infested with aphids (p>0.7). However, inbred plants were more likely to be infected by viruses, whether or not they were sprayed (p<0.0001). Plants from which herbivores were excluded by spraying produced more staminate flowers (p<0.0001), faster growing pollen tubes in vitro (p<0.005), more pistillate flowers (p<0.0001), and larger fruits (p<0.004). Similar trends were observed in comparisons between outbred and inbred plants. Significant correlations were observed between virus infestation and pollen tube growth rate (r2=-0.42, p<0.0001), fruit number per plant (r2=-0.24, p<0.0001), and fruit volume (r2=-0.15, p<0.015). These results demonstrate that a plant's probability of exposure and its resistance to disease are affected by its level of inbreeding.
Key words: mosaic virus, Cucurbita pepo, inbreeding, diabroticite beetle