Eighteen isozyme systems were surveyed in the peach
[Prunus persica(L.) Batsch.] plant introduction collection. Seven systems were polymorphic. Three previously unreported isocitrate dehydrogenase (IDH; EC 188.8.131.52), three malate dehydrogenase (MDH; EC 184.108.40.206) and two shikimate dehydrogenase (SDH; EC 220.127.116.11) banding patterns were detected in the clones. Isocitrate dehydrogenase was dimeric in structure, with two alleles present at a single locus. Malate dehydrogenase was dimeric in structure, with three alleles present at the fast locus, while a second locus was monomorphic. Shikimate dehydrogenase was monomeric, with one allele present in most clones, while PI 113452, PI 113650, and PI 117679 were heterozygous for a slow SDH allele. Electrophoretic evidence suggests PI 113452, PI 113650, and PI 117679 are peach almond (P. dulcisWebb) hybrids, since they were heterozygous for alleles previously reported only in almond.