ISOZYME PHENOTYPES SUPPORT THE INTERSPECIFIC HYBRID ORIGIN OF PRUNUS-XDASYCARPA EHRH

The black or purple apricot, Prunus xdasycarpa Ehrh., has been reporte d to be a naturally occurring interspecific hybrid between apricot (Pr unus armeniaca L.) and myrobalan plum (P. cerasifera Ehrh.). The isozy me phenotypes of five black apricot clones support its hybrid origin s ince each one has at least two plum specific and two apricot specific alleles. Prunus xdasycarpa Ehrh., commonly known as the purple or blac k apricot, was first recorded in 1755 (8) and described in 1791. It be longs to the section Armeniaca (Miller) Koch (9). In the beginning of the twentieth century Schneider speculated that it was a natural hybri d between P. cerasifera Ehrh. and P. armeniaca L. (5). Evidence from s everal studies supports the proposed hybrid origin of P. xdasycarpa (3 , 6, 7). This species is intermediate between P. cerasifera (myrobalan plum) and P. armeniaca both morphologically (leaves, fruit, flowers) and physiologically (time of bloom, cold tolerance and tolerance to fu ngal diseases). Most clones of P. xdasycarpa are not highly fertile an d produce abortive seeds with poor germination and have flowers with d efective pollen as is observed in artificially produced plum x apricot hybrids. In addition, plants of the black apricot are only sporadical ly found where the distributions of apricot and the myrobalan plum ove rlap. The purpose of this study is to provide additional evidence of h ybrid origin of P. xdasycarpa via isozymic analysis.