QUANTITATIVE ASSESSMENT OF COROLLA SHAPE VARIATION IN MEXICAN SOLANUM SECT PETOTA

Authors: VAN DEN BERG, RONALD - WAGENINGEN UNIV NETHERLND; Spooner, David

Submitted to: Solanaceae International Congress Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 2/7/2000
Publication Date: N/A
Citation: N/A

Interpretive Summary: The United States and Mexico have about 30 wild potato species. Many of them have tremendous disease resistances of value to our commercial potato breeders. Many of these species are very similar to each other however and it is unclear how many species occur in this area. Because species are used to help us make predictions of clusters of disease resistances and other useful traits we reinvestigated prior ideas of the species limits of Mexican wild potatoes. The shape of the flower part known as the corolla has been used to help define and recognize species from Mexico and the United States. We found that corolla shapes from this region failed to practically distinguish most species from this area, and we think that there are many less than 30 species there. These results will help us to better classify and organize the world's living collections of wild potatoes into fewer, more naturally defined species.

Technical Abstract: Corolla shapes in wild potatoes vary from stellate to rotate, and have been used as major morphological features to distinguish species, series, and superseries. In preparation of a potato flora of North and Central America, we found that corolla shapes, and associated corolla acumen lengths, have been used to distinguish the series Demissa, Longipedicellata, and Tuberosa. However, we found these corolla characters difficult to apply in both herbarium and living material. To better assess corolla sizes and shapes as taxonomic characters in the North and Central American wild potatoes we pressed flowers of germplasm accessions grown in a common field plot. We measured corolla radius, two assessments of shape, and absolute and relative length of acumens. The corolla measurements failed to practically distinguish most these three series. However, there were statistically significant differences of widely overlapping ranges for radius of corolla that distinguished series Longipedicellata from series Demissa (to the exclusion of S. demissum that we ally with members of the South American series Acaulia) and series Tuberosa. Their wide overlap in ranges of size greatly reduces their utility as practical taxonomic characters.