Geographical Distribution of Chromosomal Prime Types in Datura stramonium

Data are presented an the distribution of chromosomal prime types (PT's) in 583 races (287 purples, 289 whites and 7 races which were heterozygous for P and W) from 362 loci exclusive of 51 races from Botanic Gardens and commercial firms. Prime types found in nature consist exclusively of races produced by segmental interchange between non-homologous chromosomes in terms of a standard race, PT 1. With the exception of two single races, only five prime types (PT's 1, 2, 3, 4, 7) have appeared in our collections. Some areas are represented by a single PT or PT association. Thus, all the races from Eastern Europe with the exception of one race from Russia and all the races from Asia with the exception of Japan are white-flowered PT 2; all the races from Brazil are PT 1 and also have white flowers; all the races from Peru are PT 3 associated with PT 2. In some areas a mixture of types has been found, for example, in Southwestern Europe, the West Indies and Central America. In the United States most of the races are purples and predominantly PT 1 with PT's 2, 4 and 7 occurring scattered within the eastern area. Whites are found more frequently among the PT 2's than among the PT 1's, a fact which suggests that PT 2 was introduced into this region as a white rate from Europe or Africa where white PT 2's are predominant. Prime type 3 has always been found associated with PT 2 which latter PT is the one most widely distributed. lt is concluded that PT 3 probably arose in a PT 2 race. The two other species of the stramonium group, D. quercifolia and D. ferox, have been found within the range of the “Peruvian” PT 2-PT 3 rate. Since the tester races of these two species both have the four chromosomes of PT 2 and PT 3, it is suggested that these two species are phylogenetically related to D. stramonium through PT 2 and 3. Prime type 2 chromosomes are found in the majority of the Datura species tested. Prime type 4 and PT 7, however, appear to be limited to D. stramonium.