PALMER, REID G.1*, A.H.D. BROWN2, MARVIN P. SCOTT1, and HARRY T. HORNER3. 1USDA ARS CICGR, Ames, IA 50011 USA; 2CSIRO Plant Industry, Canberra, Australia; 3Department of Botany, Iowa State University, Ames, IA 50011 USA. - A survey of wild perennial Glycine species to assess nectar production, composition and floral morphology.
One of the limitations for the commercialization of hybrid soybean is the low level of
cross-pollination in seed production fields. Insect-mediated cross-pollination is the
method of choice but limited information is available in soybean on insect/flower
attraction. Out-crossing in the wild perennial soybean species, Glycine argyrea
and G. clandestina varied considerably, but can exceed 50% of the seed from
chasmogamous fruit in some situations. Our objective was to survey the wild perennial
Glycine species to assess nectar production and composition and floral morphology.
About 70 accessions representing 19 species of the perennial soybean were studied.
Measurements of the standard, wings and keel petals of two flowers per accession were
taken. Nectar was collected from flowers by the use of capillary tubes. Sugar
concentration was measured with a refractometer and by chemical determinations.
Large differences in floral morphology of the standard, wing and keel petals were recorded.
Total sugar concentrations varied among the species by 3 fold. Differences were noted
among accessions of the same species and among ploidy levels within a species. The
high sugar levels and floral morphology are compatible with entomophilous characteristics
that favor insect visitations. The result is enhanced levels of cross-pollination.
Key words: carbohydrate concentration, floral morphology, Glycine, nectar composition, nectar production, nectary