Abstract
K123 (Ipomoea trifida (H.B.K.) G. Don.) which was collected in Mexico, is a wild species closely related to the cultivated sweet potato, I. batatas (L.) LAMK. (.NISHIYAMA 1959, NISHIYAMA, FUJISE, TERAMURA, and MIYAZAKI 1961). In th:e present work, the physiological and ecolo-gical characters of K123 were studied in comparis-on with those of I. batatas. There was observed a considerable variation in the development of stems, leaves and roots, in different clones (or 20 seedlings from the original K123) as well as under different growth conditions. Generally all clones of K123 were very similar to I. batatas, but were clearly different in some characters (Figs. 1 and 2). The flowering begins in July in a few clones, but in September in most clanes of K 123, though the number of flowers are usually limited in the natural condition. Artificial treatments such as grafting and double treatments (grafting and short-day) were g:enerally effective in promoting the date of flowering and in increasing the number of flowers, although the effect of each treatement was different by clones (Figs. 3 and 4). In order to obtain a measure of self- or crossincompatibility of the clones, germinationl of pollen grains artificially dusted on the stigma was observed. Out of 20 clones of K123, 17 were self-incom-patible, 2 incompletely self-compatible, and 1 self-cornpatible. Based on the results of crossincompatibility tests among these 20 clones, about 7 cross-incompatibility groups were identified. All the clones of K 123 were cross-compatible with 4 different cross-incompatibility groups of I. batatas, except for 2 clones which were either reciprocally or non-reciprocally incompatible with certain incompatibility groups of I. batatas (Table 1). In a preliminary observations some clones of K123 were found to be resistant to ceatain nematodes (Protylelchus pratensis and Heterodera mariolei) and also to black rot (Ceratostomella fimbriata).
