Enhancing sorgoleone levels in grain sorghum root exudates.

Sorgoleone, found in the root exudates of sorghum [(Sorghum bicolor (L.) Moench], has been a subject of continued research. Sorgoleone production in grain sorghum roots was investigated under different growth conditions. Methanol was the most effective solvent for extracting sorgoleone from grain sorghum roots. Sorgoleone production is high in young developing plants. The maximum concentration (microg mg(-1) root dry weight) was produced in 5-d-old seedlings; beyond this age, production declined. However, considering both root weight and sorgoleone content per seedling, 10-d-old seedlings had the highest total amounts (microg). Compared with the control, sorgoleone content increased 6.1, 8.6, and 14.2 times when sorghum seeds were treated with auxins, Hoagland solution, and a combination of auxins and Hoagland solution, respectively. Among the innate immunity response elicitors, cellulose (an elicitor of plant origin) stimulated higher sorgoleone production than the others, and it produced 6.2 times more sorgoleone than the control. Combined treatment of sorghum seeds with half strength Hoagland solution and 5 microg ml(-1) of IBA significantly increased both root growth and sorgoleone content in sorghum seedlings.