Competitive Advantage of an Introgressed Transgene in the Presence of Zucchini Yellow Mosaic Virus on the Male Function of Cucurbita pepo ssp. texana
Open Access
- Author:
- Weakland, Danelle Rae
- Area of Honors:
- Biology
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Andrew George Stephenson, Thesis Supervisor
Dr. Stephen Wade Schaeffer, Thesis Honors Advisor - Keywords:
- Cucurbita pepo
virus resistant transgene
Zucchini Yellow Mosaic Virus
competitive advantage
selective benefit - Abstract:
- Transgenes are commonly used in the agricultural industry in order to create disease resistant plants. In turn, this reduces the need for pesticides and increases crop yield. However, gene flow between cultivated and wild crops is a well-documented phenomenon, resulting in the escape of the transgene into wild plant populations. The escape of the transgene can potentially have adverse effects on the surrounding environment and nontarget species. We examined the competitive fitness of an introgressed virus resistant transgene in our pathosystem of Cucurbita pepo ssp texana (wild gourd) while an epidemic of Zucchini Yellow Mosaic Virus (ZYMV) spread. In a field study utilizing wild gourd that was either introgressed with a virus resistant transgene (VRT) or non-introgressed (virus susceptible), we examined the frequency of seeds sired by the transgene as a viral epidemic of ZYMV circulated in the system. Four identical fields containing both transgenic and nontransgenic wild gourds were established. An epidemic of ZYMV was initiated early in the season within two fields, and spread rapidly among susceptible plants. A viral epidemic was not started in the remaining two fields. Within the virus fields, we found transgenic plants to have greater flower production as compared to virus-infected plants. Using DAS-ELISA, we calculated the transgenic frequency of seeds sired by the transgene within virus and healthy fields, and saw that virus-infected fields had a higher frequency suggesting a selective advantage of the transgene. This study demonstrates the competitive advantage of the VRT in the Cucurbita pathosystem in the presence of ZYMV. In a subsequent study, we examined the competitive ability of pollen produced by virus-infected plants in order to determine the effect of disease on male fitness. We pitted virus-infected pollen against healthy pollen, and determined that viral infection significantly reduces pollen competitive ability, suggesting that viral infection adversely impacts male reproductive fitness. The fact that pollen from virus infected plants is less competitive than pollen from uninfected (healthy) plants may partially explain why the transgenic frequency of seeds sired in virus fields is higher than the frequency in healthy fields.