ARS | Publication request: Determining Ploidy Level in Guayule Breeding Populations

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: June 10, 2010
Publication Date: October 30, 2010
Citation: Coffelt, T.A., Gore, M.A., and Ray, D.T. (2010). Determining Ploidy Level in Guayule Breeding Populations. Meeting Abstract.

Technical Abstract: The domestication and cultivation of guayule (Parthenium argentatum Gray) as a perennial natural rubber crop has been intermittent in the southwestern United States, thus its continued genetic improvement through modern plant breeding is vitally needed to realize yield potential and suitability for commercialization. Natural differences in ploidy levels among individuals are one of several factors that have slowed the rate of genetic gain in guayule breeding programs, thus knowledge of ploidy levels in guayule germplasm would help to accelerate the development of stable, high yielding cultivars. To that end, we adapted flow cytometry—a rapid and simple alternative to laborious chromosome counting—for ploidy level analysis in guayule. With the implementation of flow cytometry, we examined the ploidy levels of 34 guayule accessions available from the National Plant Germplasm System. A natural polyploid series that ranged from diploids (2n=2x=36) to pentaploids (2n=5x=90) was detected, with 4x as the predominant ploidy level. In addition, accessions with multiple ploidy levels (i.e., mixed ploidy) were observed, which suggests that the ploidy level of a guayule plant should not be taken for granted. Notably, linkage of our ploidy level data to that of pedigrees uncovered complex ploidy level variation in guayule breeding programs, which was found to be perfectly concordant with existing ploidy level data supported by chromosome counting. Importantly, this work serves as the basis for future breeding efforts as well as QTL analysis and association mapping studies in guayule.