Abstract
Ploidy manipulation and the resulting need for rapid ploidy screening can be important in potato research and breeding programs. We tested three predictors of ploidy, particularly seeking the quickest, simplest, and most reliable: Chloroplast number per guard cell (C#), guard cell length (GC), and pollen diameter (P), with a total of seven variations in methods of preparation. Time required for each preparation was assessed, and a panel of inexperienced volunteers compared these methods for accuracy using a standard set of coded samples of known ploidy. The common method of counting C# with iodine stain took longer and was no more accurate than observing C# or GC in tap water. GC from 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, so experience and care in selecting a representative sample of cells contributes to accuracy. The standard measurement of P after staining with aceto-carmine was faster to prep and just as reliable as epidermal methods for some technicians, even with no previous experience. Pursuit of ultra-simplified methods led us to measure P in tap water. Diameters of pollen in plain water are significantly larger, but only for living pollen, suggesting this method might also be developed into a rapid and reliable way to estimate pollen viability.
Published Version
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