A germplasm collection of 59 Schlumbergera Lemaire clones was assayed for isozymes of aspartate aminotransferase, glucose-6-phosphate isomerase, leucine aminopeptidase, malate dehydrogenase, phosphoglucomutase, shikimate dehydrogenase, and triosephosphate isomerase. The collection included cultivars of holiday cactus [S. truncata (Haworth) Moran and S. ×buckleyi (T. Moore) Tjaden] plus accessions of S. kautskyi (Horobin & McMillan) N.P. Taylor, S. opuntioides (Löfgren & Dusén) D. Hunt, S. orssichiana Barthlott & McMillan, S. russelliana (Hooker) Britton & Rose, S. ×exotica Barthlott & Rauh, and S. ×reginae McMillan & Orssich. Twelve loci with 36 alleles were detected. Percent polymorphic loci, mean number of alleles per locus, and mean heterozygosity were 83, 3.00, and 0.24, respectively, for the entire collection. Forty-one clones (69%) could be distinguished solely on the basis of their isozyme profiles, but the remaining 18 clones shared profiles with one or two other clones. Isozymes proved useful for determining the parentage of some clones and verifying that some progeny were interspecific hybrids. About 28% of the genetic diversity within the entire collection is unique to four Schlumbergera species that have scarcely been exploited for breeding holiday cactus cultivars.
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