Molecular Characterization of Wild Beta Populations in the Imperial Valley, California

Populations of wild Beta species exist as weeds in commercial sugar beet fields in the Imperial Valley, California. Significant losses to sugar yield and quality result if these wild plants are not removed. In cases of extreme infestation, fields are abandoned without harvest. No selective chemicals are available to differentiate conventional sugar beet from wild relatives and hand removal is labor intensive and expensive. Planting sugar beet varieties with tolerance to glyphosate is a potential solution for infested fields, but risk of gene flow to adjacent wild relatives must be determined. Previous research identified these populations as either Beta vulgaris subspecies maritima or Beta macrocarpa. This distinction is critical because B. v. ssp. maritima will readily cross hybridize with cultivated sugar beet while B. macrocarpa rarely will. In April 2011, whole plants, mature seed, and leaf tissue for DNA extraction were collected from wild plants in 25 infested sugar beet fields throughout the Imperial Valley. Morphology of plants from collected seed grown in non-competitive conditions assigned taxonomy of these populations to Beta macrocarpa. In this study, we used molecular tools with the objective to determine genetic similarities and differences between and within wild Beta populations. DNA was extracted from collected leaf tissue and DNA of known B. v. ssp. maritima and B. macrocarpa accessions was included for comparison. Six simple sequence repeat (SSR) molecular markers were run and fluorophore-assisted fragment analysis assigned sizes to resulting PCR products. Marker data was evaluated for population structure. The DK statistic divided the wild Beta populations into two subgroups suggesting gene flow occurred either amongst wild beet populations or between cultivated and wild beets at some point in their history. Phylogenetic analyses are underway to further clarify these relationships.