Abstract: Wide adoption of a few of homogeneous germplasm would reduce crops' genetic diversity, increase crop vulnerability stresses, and reduce the stability of crop production. The introduction and utilization of exotic germplasm is a sustainable solution for broadening the genetic diversity and promoting periodical replacement of varieties. The genetic contribution and economic impacts of exotic genetic resources (particularly that of US and CG resources) on China's maize production were evaluated on the basis of analysis of varieties' pedigree information from 20 major maize-producing provinces in China from 1982 to 1997. The results indicated that the contribution of US and CG germplasm resources to the continuous increase of China's maize production, particularly CG gerplasm resources, has shown a rapid increase trend since the 1990s. The genetic contribution of US germplasm resources increase by 1%, per unit maize yield will increase by 0.2% (0.01 t·ha-1). If the contribution of CG germplsam resources, which has greater potential yield, increase by 1%, maize yield will increase by 0.025 t·ha-1. One policy should be implemented for the government is encouraging breeders to focus more attentions on the use and improvement of CG germplasm resources. The US germplasm resources have been utilized extensively in China so that they can offer germplasm resources for maize breeding and maize production.

Key words: Maize (Zea mays L.), Germplasm, Genetic diversity, US, CGIAR