Synergistic Response of Plant Hairy‐Root Cultures to Phosphate Limitation and Fungal Elicitation

The combined effects of phosphate limitation and fungal elicitation on sesquiterpene production were examined in Agrofeacterium‐transformed “hairy‐root” cultures of Hyo‐scyamus muticus Limiting the initial supply of inorganic phosphate to elicited cultures resulted in a 4.2‐fold increase in solavetivone production as compared to elicitation at control media phosphate levels (1.1 mM). Because growth was attenuated at low initial phosphate levels, production per unit cell mass increased 46 times as compared to the control. Both elicited and nonelicited cultures showed enhanced solavetivone production at lower initial phosphate levels. In fact, the specific productivity of nonelicited roots grown in phosphate‐free media was comparable to the specific productivity of fungally elicited roots that are not phosphate limited. Addition of fungal elicitors enhanced specific productivity of solavetivone about 200‐fold over nonelicited cultures at nearly all phosphate levels. Phosphate limitation and fungal elicitation are therefore synergistic, and optimal total production is achieved by simultaneous application of these two production strategies.