Morphological differentiation in Medicago sativa s.l. in relation to ploidy

A study was undertaken of the yellow-flowered and violet-flowered diploid (2n = 2x = 16) and tetraploid phases of Medicago sativa s.l., excluding the widespread hybrid derivatives between the two flower-colour variants. It was found that diploid and tetraploid yellow-flowered plants (M. sativa ssp. falcata collectively) exhibit substantially overlapping morphological variation. However, among violet-flowered plants, the examined samples of diploids (M. sativa ssp. caerulea) and tetraploids (M. sativa ssp. sativa) proved to be completely separable by discriminant analysis. Most characters of ssp. sativa are quantitatively greater than those of ssp. caerulea. This and other considerations are consistent with an autopolyploid origin.