Genetic system relationships inTrifolium

Abstract

Examination of species of Trifolium in the Kentucky collection revealed that annual species generally have simple tap roots, low chromosome numbers (2n = 10−32), are usually self-pollinating and many were introduced from a Mediterranean type climate. Perennial species generally are tap-rooted, stoloniferous, or rhizomatous, possess higher chromosome numbers than annuals (2n = 12− 130), are mostly cross-pollinating and do not have specific climate-habitat relationships. Species introduced from Eurasia are more numerous and more diverse in base chromosome number (n = 5−8) than from other origins. Only species with diploid chromosome numbers of 16 or higher are stoloniferous or rhizomatous. Rhizomatous species, mostly cross-pollinated, were introduced from Eurasia, North and South America, but not from Africa, and not often from Mediterranean climates. Self- and cross-pollinated species occur in all origins. Different flower colors and leafmarks are not associated with origins, climates, and other morphological and physiological characteristics.