Variation in flowering response to photoeriod in perennial Glycine species

The wild perennial Glycine spp. offer a potential source of new germplasm for the improvement of soybean [Glycine max (L.) Merr.], but information is needed on useful characteristics in this material. The objective of this study was to determine the flowering response of the wild perennial Glycine species to different daylengths. Twenty-five accessions of G. tomentella Hayata, one of G. arenaria Tind., and one of G. tabacina (Labill.) Benth. were grown under photoperiods of 8, 12, and 16 h at day/night temperature regimes of 28/24 and 24/20 degrees C in a phytotron. The accessions represent the latitudinal range within each of five diploid (D1-D59 and five tetraploid (T1-T5) isozymically distinct groups of G. tomentella, and include two previously allied accessions that now have been placed in separate species. The 12-h daylength was most conducive to cleistogamous and chasmogamous flower development while the 16-h day-length suppressed flowering. Plants generally took longer to reach comparable phenological stages of growth in the cooler temperature regime, but the initial flowers appeared at similar nodes in both warm and cool temperatures. Eight accessions flowered in all three daylengths. The accessions from North Queensland in the D4 (G1300, G1780) and T2 (G1769, G1146) isozyme groups were the least sensitive since they produced both flower types in all photoperiods tested and may be of value in soybean germplasm development