Modularity and selection of nectar traits in the evolution of the selfing syndrome in Ipomoea lacunosa (Convolvulaceae)

Although the evolution of the selfing syndrome often involves reductions in floral size, pollen, and nectar, few studies of selfing syndrome divergence have examined nectar. We investigate whether nectar traits have evolved independently of other floral size traits in the selfing syndrome, whether nectar traits diverged due to drift or selection, and the extent to which quantitative trait locus (QTL) analyses predict genetic correlations. We use F5 recombinant inbred lines (RILs) generated from a cross between Ipomoea cordatotriloba and I. lacunosa. We calculate genetic correlations to identify evolutionary modules, test whether traits have been under selection, identify QTLs, and perform correlation analyses to evaluate how well QTL properties reflect the genetic correlations. Nectar and floral size traits form separate genetic clusters. Directional selection has acted to reduce nectar traits in the selfing I. lacunosa. Calculations from QTL properties are consistent with observed genetic correlations. Floral trait divergence during mating system syndrome evolution reflects independent evolution of at least two evolutionary modules: nectar and floral size traits. This independence implies that adaptive change in these modules requires direct selection on both floral size and nectar traits. Our study also supports the expected mechanistic link between QTL properties and genetic correlations.

Diuron Reduces Absorption and Translocation of Glyphosate in Sharppod Morningglory (Ipomoea Cordatotriloba)

Experiments were conducted to evaluate sharppod morningglory control with postemergence herbicides used in cotton and to determine the influence of diuron on glyphosate efficacy. Glyphosate plus diuron was one of the most efficacious herbicide treatments in the field experiment, providing up to 78% control of 10- to 20-cm stem length sharppod morningglory. In growth-chamber experiments, mixtures of either 420 or 840 g ai/ha diuron plus glyphosate potassium salt at 840 g ae/ha were needed to significantly reduce sharppod morningglory biomass. Compared to published results with otherIpomoeaspp. and field bindweed, sharppod morningglory absorbed more and translocated less glyphosate after 72 h. Retention of glyphosate in treated leaves increased when the glyphosate was mixed with 420 g/ha diuron. Mixture with 420 or 840 g/ha diuron reduced the concentration of glyphosate in roots; however, only 2% of glyphosate alone was translocated to the roots. These results indicate that the combination of glyphosate with diuron improves aboveground sharppod morningglory desiccation, but limits glyphosate translocation.

PCIB Enhances Regeneration of Ipomoea cordatotriloba Dennstedt Leaf Explants and Protoplasts

Leaf callus of Ipomoea cordatotriloba was initiated by culturing explants on Linsmaier and Skoog medium containing 3 g yeast extract/liter, 18.9 μm ABA, 2.3 μm 2,4-D, and 0.15 m sucrose. Calluses were transferred to Murashige and Skoog media containing 17.8 μm BA and 0, 1, 10, or 100 μm PCIB. The number of shoots from calluses grown on medium containing 10 μm PCIB increased significantly, and the percentage of calluses exhibiting shoot regeneration almost doubled compared to calluses grown on regeneration medium without PCIB. Protoplasts isolated from stem and petiole tissues of in vitro-grown plants were cultured in Kao and Michayluk 8p medium to the callus stage. Calluses (4-6 mm) were transferred to the callus induction and regeneration media used to regenerate leaf-explant callus. Of the protoplast-derived calluses cultured on media containing 10 or 100 μm PCIB, ≈13% and 18%, respectively, regenerated shoots after 2 months; none regenerated on the medium without PCIB. Chemical names used: abscisic acid (ABA); 2,4-dichlorophenoxyacetic acid (2,4-D); N6-benzyladenine (BA); α -p-chlorophenoxyisobutyric acid (PCIB).

PROTOPLAST REGENERATION OF IPOMOEA CORDATOTRILOBA, A SPECIES CLOSELY RELATED TO SWEETPOTATO.

The use of wild Ipomoea species in sweetpotato improvement may be facilitated by the use of in vitro techniques such as somatic hybridization. Plant regeneration from callus cultures is essential to the successful application of these in vitro techniques. This is the first report of plant regeneration of I. cordatotriloba from protoplast derived calli. Protoplasts isolated from petiole and stem tissues of in vitro grown I. cordatotriloba were initially cultured on KM8p media. All calli cultured regenerated roots after 1 month on regeneration media. Approximately 13% and 19%, respectively, of the calli cultured regenerated shoots after 2 months on media containing 10 and 100 uM parachlorophenoxy isobutyric acid (PCIB). Regenerated shoots developed into whole plants when transferred to MS media without hormones. The regenerated plants closely resembled the parent's morphology.