An Immunoelectrophoretic Comparison of Three Species of Coffea

Abstract

Seed proteins from three Coffea species were compared using immunoelectrophoretic procedures. Nine precipitin bands appeared when two-dimensional immunoelectrophoresis (IE) was used with C. canephora antigen and antiserum, but only six bands appeared in conventional IE. Of these nine bands, C. arabica shared eight and C. robusta six. One band of C. canephora was unique. Quantitative studies with rocket IE showed that C. canephora had very high serological correspondence with C. arabica, but C. robusta is 30% lower. The three major rocket patterns are believed to be bands II, V, and VI on the two-dimensional IE plate, and their measurement was representative of the degree of total protein similarities among the species. These results provide a basis for additional taxonomic investigations of Coffea. The taxonomic relationships in Coffea are complex and poorly understood. Since Linnaeus described the genus it has had considerable attention. Houk (1939) listed 190 species in Coffea but he recognized only 86. Thirty-five were cited by de Candolle (Wellman, 1961). Other taxonomists such as de Wildeman (1901), Chevalier (1947), Coste (1955), and Wagenitz (1964) recognized 80, 87, 60, and 50-60 species, respectively. Data available to early taxonomists came from morphology, anatomy, and geographic distribution. No classification has received general acceptance. There is also confusion and disagreement concerning the number of Coffea varieties, cultivars, hybrids, and mutants. Except for the studies of Payne et al. (1973, 1976), modern approaches and multidisciplinary criteria have yet to be applied to the delimitation of Coffea. Payne et al. used disc-electrophoretic patterns of proteins and isozymes of malate dehydrogenase to make dendrograms for Coffea species, varieties, and cultivars. Affinity relationships were proposed which were based on these dendrograms. Lee and Fairbrothers (1978) employed serological methods in a systematic investigation of selected taxa of Rubiaceae and putatively related families. They produced a threedimensional model showing serological relationships obtained with a photronreflectometer. In their Ouchterlony plates and immunoelectrophoresis (IE), five or six bands in C. canephora and four or five bands in C. arabica were reported when using C. canephora antiserum. Coffea seed protein extracts are strongly antigenic, giving sharply deI I thank David E. Fairbrothers for help, including seed materials, and David B. Dickinson for laboratory facilities and suggestions. This work was supported in part by Health, Education, and Welfare grant Al-12879, National Science Foundation Grant BMS75-17805, and the Illinois Agricultural Experiment Station. 2 Horticulture, University of Illinois, Urbana IL 61801.