Root master

Sorghum is something of an unknown in the Western diet. Originating in Africa, it is widely grown in dry regions because of its drought tolerance and is a staple grain for many people. In the southern US, it is also grown but almost exclusively for livestock fodder. However, it has recently seen an explosion of interest because of the presence of compounds thought to have anti-cancer properties and its suitability for the diets of the growing number of people with gluten intolerance. In addition, it can taste rather good: researchers at the US Department of Agriculture's research service laboratory in Manhattan, Kansas, are now assessing sorghum varieties that may lead to better loaves of bread and other baked products, traditionally entirely wheat-based. But for some researchers the crop is of other significance. It is known to be one that appears able to resist competition from weeds. Other plants with this property, allelopathy, include black walnut, fescue and rice. Scientists at the Natural Products Utilization Research Unit at Oxford, Mississippi, are studying sorghum as it exudes a compound called sorgoleone, a substance that appears more active in fighting weeds than most others. " We wanted something very active that's produced by the root and root hairs in fairly high amounts. Nothing else we've seen fits these criteria as well as sorghum and sorgoleone do, " says team member, Franck Dayan. " Crops have been bred and engineered to defend against nematodes and diseases, " says Stephen Duke, the unit's head. " But almost nothing has been done to help crops fend off weeds, other than making them resistant to synthetic herbicides. " The team, together with colleagues at the University of Georgia, is now studying the genes involved in the production of sorgoleone in sorghum roots. The initial goal is to see if improved sorghum strains can be developed but the team also hope to explore the possibility of transferring the ability to fend off weeds to other species. " Allelopathy as a means of weed control has fascinated scientists since the early twentieth century, " says Duke.