Temperature and Soil Moisture Drive Coumestrol Concentration in Annual Medicago spp. in the Presence but Not Absence of Phoma Black Stem and Leaf Spot (Phoma medicaginis)

Studies were undertaken to determine the impact of environmental variables temperature (12.5/9.5, 20/17, 27/24 °C day/night) and soil moisture (100, 50% WHC), their interaction with Phoma medicaginis infection, on production phytoestrogen coumestrol in annual Medicago rugosa cv. Paraponto M. scutellata Sava. Disease factors measured included leaf disease incidence/severity, petiole/stem yellowing severity. Coumestrol levels determined using gas chromatography–mass spectrometry (GC–MS). Increasing from 12.5/9.5 inoculated plants significantly (p < 0.05) increased 193 mg kg−1 390 kg−1, but there no differences across all three temperatures uninoculated plants. Reducing 100% WHC at highest (27/24 °C) caused greatest increase 156 269 The (600 kg−1) was under °C/50% for Sava infected P. least (1.6 20/17 absence medicaginis. Clearly, situations higher conjunction lower cause elevation presence medicaginis, far exceeding animal risk threshold 25 kg−1.