* Corresponding author. Tel.: #31-317476966; Fax.: #31-317418094; e-mail: g.booy@cpro.dlo.nl. Biochemical Systematics and Ecology 26 (1998) 199 — 224 Variation in the enzyme esterase within and between ¹ ulipa species; usefulness for the analysis of genetic relationships at diﬀerent taxonomical levels Gerdien Booy*, Leonard W.D. Van Raamsdonk Centre for Plant Breeding and Reproduction Research (CPRO-DLO), P.O. Box 16, 6700 AA Wageningen, The Netherlands Received 11 April 1997; accepted 20 June 1997 Abstract Intra- and interspeciﬁc variation in bulb scale esterases of ¹ulipa species were investigated to determine the usefulness of this marker for the assessment of genetic variation within the genus ¹ ulipa. At the population level, esterases appeared to be suitable markers. Diﬀerent bulbs of a population, which were analyzed for polymorphisms in their esterases using native PAGE next to other accessions from the same species, generally formed a separate group after cluster analysis. In some of these cases, genetically related accessions clustered within the population cluster. Within section ¹ulipa, which consists of relatively closely related species, esterases also proved to be useful for analysis of genetic variation at the species level, since the accessions from each species formed separate clusters. However, within section Biﬂores, which consists of more distantly related species, cluster analysis on the basis of esterases did not reveal clustering of all species. Clustering of the accessions within both sections on the basis of bulb scale esterases was compared with relationships found using morphological data. The species of section ¹ ulipa did not form separate clusters after analysis of the morphological data, which is in contrast to the results from esterase analysis. However, all accessions of section Biﬂores clustered together per species based on the morphological variation.  1998 Elsevier Science Ltd. All rights reserved Keywords: ¹ulipa; Tulip; Species; Electrophoresis; Isozymes; Esterase; Intraspeciﬁc variation; Interspeciﬁc variation. 0305-1978/98/$19.00  1998 Elsevier Science Ltd. All rights reserved. PII: S0305-1978(97)00093-8