Isoflavonoid changes in soybean cell suspensions when challenged with intact bacteria or fungal elicitors

Zacharius R. M.; Kalan E. B.

Glycine max (L.) Merr. cv. Mandarin cell suspension cultures did not not give a typical hypersensitive respone (HR) when challenged with a fungal elicitor or an incompatible strain of the soybean leaf pathogen Pseudomonas syringae pv. glycinea (Psg). Those cultures that darkened showed a small, gradual loss of viability and accumulated the phytoalexin glyceollin. Such cultures had a much higher level of isoflavonoids than those that did not darken or produced glyceollin under biotic stress. Concurrent with the formation of glyceollin, there was a sharp decline in the level of daidzein and genistein. Genistein was identified as a major isoflavonoid of soybean cell suspensions, but occurred only in trace amounts in the intact plant. No correlation was found between the induced levels of glyceollin and constitutive levels of isoflavonoids. While daidzein may be a direct precursor of glyceollin, a high level of daidzein and perhaps genistein appeared to be indicative of a required physiological state of the culture for the stress response. Cell culture levels of isoflavonoids appeared to be elevated by light.