ISOZYME DIVERSITY IN SOUR, SWEET, AND GROUND CHERRY

Thirty-six sour (Prunus cerasus L.), sweet (P. avium L.), and ground c herry (P. fruticosa Pall.) selections were evaluated for seven enzyme systems and principal coordinate analysis was used to examine isozyme divergence among these cherry species. The enzyme systems studied were phosphoglucose isomerase (PGI), isocitrate dehydrogenase (IDH), phosp hoglucomutase (PGM), 6-phosphogluconate dehydrogenase (6-PGD), leucine aminopeptidase (LAP), shikimate dehydrogenase (SKDH), and malate dehy drogenase (MDH). The first principal coordinate, which accounted for 4 1% of the total variation, separated the diploid sweet cherry selectio ns from the sour, ground, and sour x ground cherry tetraploids. An add itional 86 selections were evaluated for up to six of the enzyme syste ms to determine the polymorphisms at the enzyme loci and the level of heterozygosity between the diploid sweet cherry and the tetraploid spe cies and interspecific hybrids. 6-PGD was the most polymorphic enzyme exhibiting 16 patterns. The tetraploid cherry species were more hetero zygous than the diploid sweet cherry with an average heterozygosity of 78% compared to 19% for the diploids.