Overwhelming evidence points to an American origin for the sweet potato Ipomoea batatas (L.) LAM. Attempts have been made to identify related diploid species from Mexico, and to use these in hybridisation experiments with L batatas. The sweet potato is a poor seed setter but abundant bloom occurs in Jamaica very late in the year.
Attempts at hybridisation between I. batatas (2n ~-90) and 1. trichocarpa (ELLIOTT) 2n ~ 30 or L gracilis 2n = 30 has been tolerably successful. A very high degree of self-incompatibility was demonstrated in all three species investigated but successful crosses were made using different plants of L trichocarpa.
An investigation of pollen viability showed that in all cases pollen could germinate but pollen tube growth was abnormal in incompatible pollinations.
I. trichocarpa hybridised readily with L batatas when the former was used as female parent. Embryo development in such a cross proceeded slowly, and stopped before cotyledon formation. No viable seeds were obtained. A comparison of embryo development in hybrid and normal seeds brought to light anomalies in development and structure of endosperm and maternal tissue in the hybrid.
[NTRODUCTION In 1855, DE CANDOLLE made mention of a current idea, that, although there was hardly any communication between peoples of America before the discovery of the New World by Columbus, there might have been two possible transfers of useful plants by man -one, the "batata" or sweet potato, and the other the coconut. Since then there has been strong support for a theory of an American origin for sweet potato. As early as 1903, O. F. COOK in his paper "Food plants of America", lists the potato as the third most important food crop of the Polynesians. In his opinion, the swee(potato must have been transferred from one continent to the other by the agency of man. He agrees with other writers, however, that America could be the original home of the plant. YEN (1960) made observations on the seed setting ability of the plant, and found a range in latitude between 30 degrees North and South of the equator. Varietal studies carried out by YEN (1964) using such variants as variation in length and width of open corolla, heterostyly and homostyly, leaf dissection, thickness of stem, hairiness of stem, purpling of stem and number and weight of tubers, led to the conclusion that variation is more pronounced in American varieties. This strongly points to an American origin. With this in mind relationship between American wild Ipomoeas and lpomoea batatas, was investigated in order to find if possible by compatibility studies,