National Citrus Germplasm Repository

　　The National Citrus Germplasm Repository （NCGR） was officially established in the 1980s in the Citrus Research Institute （CRI） of the CAAS.  The mission of the repository is to collect, preserve, evaluate and utilize germplasm of citrus and its related genera and species in the family of Rutaceae, and to conduct research related to its mission.  The NCGR is one of the 31 national crop germplasm collections administered by the Ministry of Agriculture of the PRC.

　　The germplasm repository has 15 hm2 of land.  One large area of the land is used for the preservation of clonal germplasm materials and a small piece of the land is used for the purpose of evaluating the collected materials.  There are accessory facilities including a 300 m2 laboratory, a fruit specimen exhibition room, a herbarium, and 3,000 m2 of greenhouses and screenhouses.  The laboratory is equipped with instruments for conventional and molecular studies of citrus genetic diversity, the development of better preservation, distribution, and evaluation methods, and the analysis of fruit quality.  The greenhouses and screenhouses are used for the maintenance of the accessions from tropical regions and for the quarantine of newly collected materials. 

　　Currently, there are 1046 accessions in the repository, representing 24 species and 14 variations of 9 genera in the subfamily of Aurantioideae, including 23 Fortunella spp, 92 Poncirus spp, 89 citrons, 34 papedas and junos, 31 sour oranges, 301 sweet oranges, 185 pummellos, and 413 mandarins.

　　Evaluation work has been systematically conducted for more than 25 years. Important agronomic traits such as fruit quality, juice quality, and stress-resistance are characterized in more than 700 accessions. Some elite materials have been thus identified such as late Jincheng, late Xuegan, seedless Valencia orange, And the late Penggan, etc. Some special genetic materials have been obtained such as the low acid sweet orange, the thornless trifoliata orange, and the yellow-flower citrange etc. Some of the specialties have been utilized in breeding programs or released directly to public.

　　Genetic diversity research has been focused on the development of DNA markers such as RAPD, SSR, and SNP, and in the application of the markers in the identification and classification of the accessions.  Morphological, biochemical, and palynological research has also been conducted to assess the phylogenic relationships among the accessions.  ITS sequencing of nuclear ribosomal DNA has been performed to understand at the molecular level the evolutionary relationships among the important accessions.  The construction of core collections is under way using DNA molecular markers. 　　

　　The NCGR has been maintaining a private database since the end of 1980s. The database is supposed to be uploaded to the virtual museum “national infrastructure of natural resources for science and technology” this year.