Location: Vegetable Crops ResearchTitle: Comparing methods of ploidy estimation in potato. Author
|Kramer, Lydia - University Of Wisconsin|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/30/2018
Publication Date: N/A
Technical Abstract: Ploidy manipulation and the resulting need for rapid ploidy screening is an important part of a potato research and breeding program. Determining ploidy by counting chromosomes or measuring DNA in individual cells is definitive, but takes time, technical skills and equipment. We tested three predictors of ploidy, particularly seeking the quickest, simplest, and most reliable methods: Chloroplast number per guard cell (C#), guard cell length (GC), and pollen diameter (P), with various methods of preparation. Time required for each preparation was assessed, and a panel of inexperienced volunteers compared the methods for accuracy using a standard set of coded preps of known ploidy. The standard method of counting C# with iron acetate stain took longer and was no more accurate than observing C# or GC in plain water. Water, being more easily accessible and not requiring stain preparation time, has the advantage over methods which use iodine. GC in tape impressions of the underside of leaves was reliable and has the advantage of permanent slides for later reference. We recommend GC, whether in water, stained, or as tape impressions. GC is significantly different in diploids and tetraploids, but the distributions do overlap. Thus, technicians should measure the biggest or smallest GC to avoid ambiguity. The standard measurement of P after staining with aceto-carmine was faster to prep and just as reliable as epidermal methods. Pollen has the advantage of representing the sporogeneous tissue, but the disadvantage of needing to grow plants to maturity. Pursuit of ultra-simplified methods led us to measure P in plain water. Diameters of pollen in plain water are significantly larger, but only for living pollen, suggesting this technique might also be developed into a rapid and reliable way to estimate pollen viability.