Cucurbit Genetics Cooperative Report 1:28 (article 26) 1978
Comparative Electrophoretic Analysis of Isozymes in Cucurbita Species
J. T. Puchalski and R. W. Robinson
New York Agricultural Experiment Station, Geneva, NY 14456
A chemotaxonomic investigation of 19 different species of the genus; Cucurbita, including all five cultivated species, was made on the basis of isozymic composition. The multiple molecular forms of esterase, peroxidase, and leucine aminopeptidase in young green leaves were analyzed by starch gel horizontal electrophoresis technique.
Large interspecific differences for all three enzyme systems were observed. The largest differences were for fast migrating anodic. isoesterases and for very active cathodic isoperoxidases. On the basis of the similarity of species specific isozyme patterns, all 19 species analyzed were divided into seven different groups. The first group consisted of four very similar species, C. cylindrata, C. cordata, C. digitata, and C. palmata. Cucurbita martinezii and C. okeechobeensis showed uniform patterns for all enzyme systems and were classified together with C. lundelliana into the second group The species C. foetidissima contained some unique isoesterases and was delegated alone to the third group. Two other species, C. texana and C. pepo, showed only small differences in composition of anodic isoperoxidases and some quantitative differences for isoesterases; they comprised the fourth group. Five species showing the highest heterogeneity of esterases were classified in the fifth group: C. moschata, C. mixta, C. palmeri, C. sororia, and C. gracilior. Cucurbita andreana and C. maxima had the same pattern of esterases and leucine aminopeptidases, and differed only for one peroxidase fraction. Both of these species together with the enzymatically similar C. ecuadorensis, were classified in the sixth group. Cucurbita ficifolia had some similarity to the species in the sixth group, but in addition contained some specific isoesterases and was classified separately in a seventh group.
'Seminole', a pumpkin cultivated by Indians in Florida for centuries, was previously classified as C. moschata. However, on the basis of the same zymogram pattern as C. mixta, it appears to belong to that species.
This biochemical classification of the genus Cucurbita based on isozymic composition is in close agreement to the numerical taxonomy classification of Bemis and co-workers (1) that was based on morphological characters.
- Bemis, W. P., A. M. Rhodes, T. W. Whitaker, and S. G. Carmer. 1970. Numerical taxonomy applied to Cucurbita relationships. Amer. J. Bot. 57:404-412.