Investigation of intra-specific variation in size and shape traits of leaf and stoma of greater yam (Dioscorea alata L.)

"Although greater yam (Dioscorea alata L.) is a dioecious plant, seeds for sexual reproduction are seldom observed under natural conditions. This yam is asexually propagated with tubers in ordinary cultivation. Nevertheless, a great deal of diversity is observed in various morphological traits of tuber and leaf. Intra-specific variation in the number of chromosomes has been reported, ranging from triploid (2n=3x=30) to octaploid (2n=8x=80). In the present study, genetic diversity of leaf and stoma shape within species was investigated using 12 landraces introduced from Papua New Guinea (PNG) and 22 cultivars domestically preserved. Variance and principal component analysis disclosed that this species displayed a great diversity of leaf size and shape and there was a relation between the shape of the tuber and leaf. Observation of the chromosome numbers revealed the existence of tetraploid (2n=4x=40) and octaploid (2n=8x=80) forms within the species and the octaploids tended to have larger stomata than the tetraploids."