Phytoalexins, Resistance Traits, and Domestication Status in Phaseolus coccineus and Phaseolus lunatus

Resistance to pathogenic fungi and the isoflavonoids that confer such resistance capabilities were studied in two systems of wild and cultivated Phaseolus spp. seedlings. Results for P. coccineus show a gradient in isoflavonoid diversity with pathogen resistance high in wild varieties and low in cultivated ones. P. lunatus varieties showed the same trend in resistance and cyanogenic capacity, but not in isoflavonoid diversity. It is suggested that the effectiveness of the phytoalexin natural mixture depends more on its diversity than its total levels in seedlings.     

Profiling of flavonoid conjugates in Lupinus albus and Lupinus angustifolius responding to biotic and abiotic stimuli

Qualitative and quantitative composition of flavonoid and isoflavo- noid glycosides as well as free aglycones in lupin seedlings (roots and aerial parts) grown under different light conditions or responding to infection with Pleiochaeta setosa, a fungus causing brown leaf spot, were monitored by liquid chromatography with UV and/or mass spectrometric detection. Both physical and biotic factors affected flavonoid and isoflavonoid levels in lupin tissues. Fungal infection evoked significant increase in the amounts of genistein, 2-hydroxygenistein, and their prenylated derivatives that are thought to function as lupin phytoalexins. Effect on quantitative changes of glycosylated flavonoids and isoflavonoids in the roots and aerial parts was less significant. Moreover, different light conditions applied during seedling growth caused relative changes of flavonoid and isoflavonoid conjugates composition, especially in the leaves of white lupin plants. The chemical structures of flavonoid and isoflavonoid conjugates present in Lupinus angustifolius were elucidated. In addition to genistein and2-hydroxygenistein glycosides, flavonol conjugates were identified in leaves, while the composition of root isoflavonoids was similar to that of L. albus reported earlier.