major grain crop的用法和样例：
例句
- Encouragingly, a new set of tools is revealing that some of the answers may be found by exploring the origins of the three major cereal crops.
可喜的是，现在藉由一套崭新的工具来追寻这三大主要粮食作物的起源，或许可以找到一些解答。 - But the real revolutionary potential in this method lies in its power to open up the genetic bottleneck created thousands of years ago when our major crops were first domesticated.
但这套方法真正的革新，是突破了数千年前开始栽培主要粮食作物时设下的遗传瓶颈。
