Wheeler said that scientists have not yet studied the yam's nutritional value to see what benefits the plant offers as a food crop.

怀勒说，科学家尚未对这种山药的营养成分及食用益处进行研究。

IT IS the world's fourth-most-important food crop, after maize, wheat and rice.

在世界的粮食作物中，它的重要性仅次于玉米、小麦和稻谷。

It noted the potato 'u2014 the Number 4 food crop worldwide 'u2014 is already a staple food in the diet of the world population.

这使得马铃薯——全球第四大食品作物，即将要作为全世界人民的日常主食。