Submitted to: Acta Horticulture Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: May 14, 2001
Publication Date: November 26, 2001
Citation: Bohac, J., Peterson, J.K., Jackson, D.M., Harrison Jr, H.F., Snook, M.E. 2001. Approach to selection of pest resistant sweetpotato breeding lines through identification and quantification of biochemical resistance compounds. Abstract AIII-O-1 in Guide for Participants, Sweetpotato: Food and Health for the Future, an international symposium sponsored by the International Society for Horticultural Science (ISHA), the International Potato Center (CIP), and the Universidad Nacional Agraria La Molina (UNALM), 26-29 November, 2001, Lima, Peru. Technical Abstract: Over many years, USDA researchers have developed sweetpotato breeding lines and cultivars with multiple resistances to soil insects, fungi, nematodes, and weeds. These lines were developed by using a polycross breeding technique to combine genes from diverse world germplasm sources. Resistances were identified using greenhouse screening and field evaluation. Because these resistance factors were shown to be quantitative, large populations have to be evaluated to combine all these resistances with the multitude of other traits required in a successful cultivar. It is proposed that the selection of resistant seedlings can be made more efficient through the use of bioassays and quantification for biochemical resistance factors. In studies with the multiple resistant cultivar Regal, extracts from periderm were found to be highly inhibitory to yellow nutsedge. The resin glycosides from Regal periderm accounted for rover 90% of this allelopathy. They are also toxic to insects and interfer with hyphal growth of Fusarium, and other sweetpotato pathogens. Ongoing studies have shown that other biochemical resistance factors are also found in sweetpotato cortex. Grouped as phenolics, coumarin derivatives, and unknown acids, these compounds were shown to be insecticidal and allelopathic. Periderm and cortex phenolics such as caffeic acid and p- coumaric acid were also found to play a role in general defense. The coumarin derivative scopoletin was shown to be insecticidal, fungicidal, and allelopathic. Various other "general defense" compounds were isolated and tested. Most, if not all of these compounds appear to be phytoalexins, i.e concentrations increase in response to inducers (biotic and abiotic).