Submitted to: Allelopathy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 28, 2003
Publication Date: June 15, 2003
Citation: Harrison Jr, H.F., Peterson, J.K., Jackson, D.M., Snook, M.E. 2003. Periderm resin glycoside contents of sweetpotato clones and their biological activity. Allelopathy Journal. 12:53-60. Interpretive Summary: Resin glycosides are complex molecules composed of common fatty acids and sugars. They are found at high levels in the outer skin (periderm) of some sweetpotato varieties. The purpose of this study was to assess the differences in periderm resin glycoside contents in genetically diverse sweetpotato varieties and investigate their possible biological functions. Resin glycoside contents of 37 sweetpotato varieties were measured. The highest resin glycoside content of over 10% of immediate sub-skin tissue dry weight was found in the sweetpotato variety Regal, and the lowest concentration, 0.05% was found in line W-345. Resin glycosides occur in many plants, but their biological role in plants is not well understood. They are known to cause inhibition of plants (allelopathy) grown near Regal sweetpotato, and some reports indicate that they are beneficial in the human diet. The glycoside content of the clones in our study were related to the ratings for the injury caused by the feeding of several soil insects. None of the clones with high resin glycoside levels were severely damaged by insects, but those with low levels ranged from the lowest to the highest damage ratings. We believe this indicates that resin glycosides are active in defense against insects. Because some varieties without much resin glycoside are resistant, there are other factors that also confer sweetpotato insect resistance. Resin glycoside extracted from `Regal' periderm and included in potato dextrose agar culture medium were inhibitory to the growth of four fungus species that cause rotting of sweetpotatoes. These findings indicate that the high resin glycoside levels in the periderm of some sweetpotato varieties help protect them from soil insects and fungi and confer resistance to these pests.
Technical Abstract: The total periderm resin glycoside contents of 37 sweetpotato cultivars, breeding clones and accessions from germplasm collections were measured by HPLC and were found to vary greatly between clones. The highest content was over 10.02% of the periderm dry weight, and the lowest content was 0.05%. Insect damage ratings of the clones and their periderm resin glycosides content were negatively correlated, and all clones with higher glycoside contents exhibited moderate or low injury, and all clones with high injury ratings had low contents. Resin glycosides extracted from `Regal' periderm and incorporated into potato dextrose agar medium were inhibitory to the growth of four fungus species that are pathogens of sweetpotato roots. These observations provide evidence that sweetpotato resin glycosides contribute to insect and disease resistance in the roots of some sweetpotato clones.