two-line system

• 两系法

two-line system的用法和样例：

例句

1. Utilization and fixation of the distant heterosis in rice by one line method has been an exploratory work in rice breeding with great enticement and difficulty.
   通过一系法利用和固定水稻的远缘杂种优势是一项具有极大诱惑力但难度颇大的科研难题。