Immunological Studies on the Tuber-bearing Solanums

Abstract

Investigations using the Ouchtlerlony double-diffusion technique and immuno-electrophoretic analysis showed a much greater number and diversity of antigens amongst the North American species of Solomon than had been found previously amongst the South American ones. Double diffusion against antisera to S. tuberosum, S. acaule, S. iopetalum, S. bulbocastanum, and S. cardiophyllum subsp. ehrenbergii, showed a difference between the species in series Bulbocastana and Pinnati-secta, and those in series Longipedicellata and Demissa. This technique did not provide much information on the similarities or differences between the species within these two groups. However, immuno-electrophoretic analysis of the same species with the antisera to S. bulbocastanum and to S. iopetalum gave results which were easier to analyse, and provided much greater resolution of the individual species. At least one identical antigen was found in all the species studied. Some antigens were consistently present in all species in certain series, while others had no apparent significance in their occurrence. Three fast-moving antigens were found to have different, but characteristic, relative mobilities in different species in the series Bulbocastana and Pinnatisecta. The relative mobilities of these three components were similar in the two subspecies of S. cardiopkyllum and in S. sam-budnum which is considered to be a hybrid of subsp. ehrenbergii with S. pinnatisectum. A separate study on S. moreUiforme and S. clarum emphasized the distinctness of S. moreUiforme from all other potatoes, but indicated that S. clarum was more closely related to S. bulbocastanum and subsp. ehrenbergii than to S. tuberosum. With antisera to S. tuberosum and S. iopetalum on the one hand, and to S. bulbocastanum on the other, extracts of S. polyadenium were found to react more strongly than the species in series Bulbocastana and Pinnatisecta with the first two antisera, and more strongly than those in Longipedicellata and Demissa with the other antiserum. This indicated that S. polyadenium had some of the group-specific antigens from both groups, and therefore, that it may be in some intermediate position between these two major groups of species. Problems of evolutionary relationship between Mexican species and series are discussed in the light of serological, morphological, arid cytogenetical evidence.