The sex of the mother plant affects the sex variation in the offspring in Dioscorea rotundata (Poir.)

In cultivated yams Dioscorea rotundata, spontaneous sex variation occurs in the offspring despite vegetative propagation. In this study, sex variation was investigated as a function of the region (head, middle, or base) of the seed-tuber and the sex of the mother plant. Tuber-seeds were sown from the head, middle, and base regions of tubers of 6 cultivars, and germination, flowering and sex of the offspring were studied. To determine a possible relationship between the hormone content of the mother tuber and sex variation, the phytohormone profile of the head, middle, and base regions was compared in tubers from male, female, and monoecious plants. Our results showed that the region of the seed-tuber affected germination, as the germination rate of seed-tubers from the head region was 20–50 % higher than that of the middle and base regions, and they germinated 10 days earlier. The region of the seed-tuber also affected the flowering rate, which was 10–20 % higher for seed-tubers from the head region than from the base region, but it did not affect the sex of the offspring. Sex variations in the offspring were more related to the sex of the parents. Male and female cultivars had stable offspring, while monoecious cultivars had high sex variation (80 %) in their offspring. The hormonal profile of the tubers suggested a relationship between hormones and sex identity. Jasmonates and salicylic acid were more concentrated in the tubers of male and monoecious plants, while abscisic acid types, cytokinins and benzoic acid were more concentrated in the tubers of female plants. Further work is needed to clarify the role of these hormones in the control of sex expression in cultivated yam D. rotundata.