RAPID PLOIDY SCREENING OF TUBER-BEARING SOLANUM (POTATO) SPECIES THROUGH POLLEN DIAMETER MEASUREMENT

Determination of the sporophytic ploidy of numerous individuals by chromosome counting is a difficult and time consuming necessity for many genetic and taxonomic research problems. The potential for microscopic pollen diameter measurement as a fast, easy and reliable alternative method for estimating sporophytic ploidy was investigated. Contrary to popular assumptions, the diameters of large, well-stained pollen grains from plants of the same ploidy were shown to be quite consistent among a wide variety of tuber-bearing Solanum (potato) species, fitting remarkably well with expectations based on a linear relationship between ploidy and pollen grain volume (r = 0.97). Seventy-six ploidy predictions on a total of 83 coded samples were correct (92%). Although it is not effective in distinguishing 4x and 6x sporophytes, microscopic pollen diameter measurement is a very rapid and reliable method by which to distinguish 2x from 4x or 6x sporophytes.