Snow, Allison , Culley, Theresa , Ellstrand, Norman , Uthus, Kristen , Hegde, Subray .
Persistence of crop alleles in wild radish populations eight years after crop-wild hybridization.
Many cultivated species hybridize naturally with wild relatives, but little is known about whether crop alleles can persist in wild populations, especially when F1 hybrid progeny have reduced fitness. This process has important implications for understanding whether weedy populations can benefit from an influx of crop alleles, including fitness-enhancing transgenes. Wild radish (Raphanus raphanistrum) is a cosmopolitan, self-incompatible weed that is known to hybridize with cultivated radish (R. sativus). We found that crop-specific alleles persisted for at least eight generations in hybrid populations in Pellston, Michigan, USA. Four populations were established in 1996 using a 1:1 ratio of wild plants and F1 crop-wild hybrids. The sites were tilled each spring, and flowers, pollen, and seeds were sampled each summer through 2003. Initially, F1 hybrids had reduced fitness relative to wild genotypes, but the populations quickly regained wild-type fecundity by losing a reciprocal translocation and other deleterious crop genes. Initial frequencies of the three crop-specific alleles were 0.25 in each population. Recombination and natural selection allowed the populations to absorb the two crop-specific allozyme markers at relatively high frequencies in all populations. In the F8 generation, frequencies of crop-specific alleles averaged 0.26 for PGM and 0.14 for GPI. In contrast, frequencies of the crop-specific white petal allele (a dominant Mendelian trait) were only ~0.03-0.06. Overall, frequencies of crop-specific alleles varied considerably among locations, years, and loci. This study provides a clear example of how easily certain crop alleles can become established in weed populations, while others remain rare or disappear.
1 - University of California, Botany and Plant Sciences, Riverside, California, 92521
2 - Ohio State University, Depatment of Evolution, Ecology and Organismal Biology, 318 W. 12th Ave., Columbus, Ohio, 43210-4321, United States
3 - University of Cincinnati, Department of Biological Sciences, 614 Rieveschl Hall, Cincinnati, Ohio, 45221-0006, USA
Presentation Type: Paper
Location: Peruvian (Cliff Lodge)
Date: Wednesday, August 4th, 2004
Time: 4:30 PM