Foliar application of elicitors alters isoflavone concentrations and other seed characteristics of field-grown soybean

Abstract

Soybean [Glycine max (L.) Merr.] is a key species used by the nutraceutical industry, as it contains isoflavones that have beneficial effects on human health. A 2-yr field study was conducted in Sainte-Anne-de-Bellevue, QC, to determine the effects of foliar application of elicitor compounds on isoflavone concentrations of seeds, seed yield, and other important seed characteristics. Two soybean cultivars (AC Proteina and AC Orford) were treated with one of four elicitors: lipo-chitooligosaccharides (LCO) Bj V (C18:1 MeFuc) and Bj V (Ac, C16, MeFuc), chitosan, and actinomycetes spores (Streptomyces melanosporofaciens strain EF-76), each applied at two soybean stages of development [vegetative (V4), and early podding (R3)]. Untreated controls were also included. Total and individual isoflavone concentrations were determined by HPLC. Seed yield, 100-seed weight, seeds per pod, pods per plant and oil and crude protein concentrations were concurrently determined. Total and individual isoflavone concentrations were affected by year and cultivar, which also interacted with elicitors. Interactions indicated that plant response to elicitors varied greatly depending on cultivars and years. Compared with an untreated control, some elicitors resulted in total isoflavone concentration increases ranging between 67 and 87%. No single elicitor treatment, however, consistently increased isoflavone concentrations. There were three-way interactions (year, cultivar and elicitors) for seed yield and number of pods per plants indicating, again, substantial variation in response to elicitors. Response was much greater in 2004, where elicitors consistently increased seed yield and number of pods per plant. Elicitors did not affect crude protein and oil concentrations. The use of elicitor compounds seems promising as a means of increasing isoflavone concentrations and seed yield; evaluations in a greater number of environments are now required. Key words: Soybean, isoflavone, daidzein, genistein, glycitein, protein, oil, seed yield, chitosan, actinomycetes, lipo-chitooligosaccharides