Response of soybean fungal and oomycete pathogens to apigenin and genistein

Plants recognise invading pathogens and respond biochemically to prevent invasion or inhibit the colonisation of plant cells. Many plant defence compounds are flavonoids and some of these are known to have a broad spectrum of biological activity. In this study, we tested two flavonoids, apigenin and genistein, in amended culture media against seven soybean pathogens, including Colletotrichum truncatum, Macrophomina phaseolina, Phoma exigua, Phytophthora sojae, Pythium ultimum, Rhizoctonia solani, and Sclerotinia sclerotiorum. Both compounds restricted growth of all seven pathogens, although not all equally. For example, inhibition of growth was less (P & 0.05) for C. truncatum than the other pathogens tested. There also was a dosage effect as increased concentrations of either compound significantly (P & 0.05) restricted colony growth. The results suggest that through metabolic engineering, apigenin and genistein may be targets for overproduction in planta to enhance disease resistance in soybean to fungal and oomycetes pathogens.