Variation in accumulation of isoflavonoids in Phaseoleae seedlings elicited by Rhizopus

• Germination alone poorly induced isoflavonoids of Phaseoleae seeds.
• Application of Rhizopus to Phaseoleae seedlings induced isoflavonoids extensively.
• The inducibility of diverse isoflavonoid subclasses varied per Phaseoleae species.
• The kind of molecules induced followed the phylogenetic relationship.
• The amounts of isoflavonoids induced did not follow the phylogenetic relationship.

Seeds from seven species of tribe Phaseoleae, i.e. Phaseolus, Vigna, Lablab and Psophocarpus, were investigated for inducibility of isoflavonoids by germination with or without subsequent elicitation with Rhizopus oryzae. Germination alone poorly induced isoflavonoid production (in the range of 0.2–0.7 mg representative compound equivalents (RCE)/g DW), whereas application of Rhizopus onto the seedlings increased the isoflavonoid content considerably (in the range of 0.5–3.3 mg RCE/g DW). The inducibility of different isoflavonoid subclasses in seedlings with Rhizopus varied per species. Isoflavones and isoflavanones were mainly found in elicited seedlings of Phaseolus, Vigna and Lablab, whereas pterocarpans were mainly observed in those of Psophocarpus. Despite their phylogenetic relatedness, the seeds of various species within Phaseoleae appeared to respond differently towards elicitation by Rhizopus during germination. The kind of molecules induced followed the phylogenetic relationship of the various species, but their amounts induced during germination, alone or combined with elicitation, did not.