2018 ASHS Annual Conference

Understanding the genome size and ploidy level of the species and specimens in our beardtongue (Penstemon Mitch.) breeding program is essential to making appropriate crosses, and to assess the success of induced polyploid plants. Frequently in plants, flow cytometry (FCM) analysis is used to estimate the genome size of a specimen in question by comparing it with an internal standard of a known plant genome size. FCM generally requires fresh tissue and uses a fluorescent dye to stain the nuclei of the cells, where they are then passed through a laser. The fluorescence of the DNA is measured and compared to the internal standard. Unfortunately, fresh tissue is not always available to immediately process for analysis. We have read in the literature that FCM has been used to identify the genome size of well preserved herbarium samples. We hypothesized that other types of stored tissue may be used in place of fresh tissue. To test our hypothesis we compared FCM analysis of fresh tissue to samples stored in -20⁰ C, -80⁰ C, lyophilized fresh tissue, lyophilized frozen tissue stored at -20⁰ C and -80⁰ C, and air dried (herbarium specimens).We examined each treatment, in triplicate with tissue from (Penstemon eatonii, P. fruticosus, P. cyaneus, P. laevis, P. palmeri, P. venustus). We found that, compared to fresh tissue, all treatments showed degradation up to a 35% reduction in genome size. Contrary to our hypothesis, this reduction in genome size was not uniform across treatments for each species. It was concluded that with the current technology and procedures, there does not exist a good substitute for fresh tissue in the collection of FCM data of plant genomes.