Citron germplasm in Yunnan, China

The center of origin and diversity for citron (Citrus medica) is Southwestern China, Northeastern India, andadjacent regions of Southeast Asia, but very little is known about citron germplasm resources in this area. Citrongermplasm resources are rapidly being eroded as forests are cleared for development and farmers abandoncitron cultivation for more profitable crops. Starting in 2008, researchers for the Chinese Citron GermplasmProject travelled around Yunnan and other provinces of China, observing both cultivated and wild citron. Wecollected information about germplasm, horticultural practices, and economic uses, as well as cuttings andseeds, which were used to establish a germplasm collection with 30 accessions in Jianshui, Yunnan. Wild citronstypically have smaller fruits and thinner rinds than commercial cultivars; it is likely that over the centuriesfarmers have selected for a thick rind, as the most economically valuable part, for preserving and eating fresh. The majority of common (non-fingered) citrons grown in Yunnan have thick, sweet albedos, but no juicevesicles. Some grow as large as 15 kg, making them the largest known citrus fruits. Common citron cultivarsinclude 'Large Wrinkled', 'Small Wrinkled', 'Pillow', 'Sour', 'Water', 'Dog Head', 'Bullet', 'Yunnanensis', 'Oblate',and 'Stigma Persistens'. Fingered (Buddha's Hand) citrons are grown primarily as ornamental plants and to bedried for use in Chinese Traditional Medicine, but also for candying. Many distinct cultivars exist, which vary inflower color, size, thickness of fingers, and the point at which the fingers branch out from the body of the fruit. Fruit types of fingered citron include the common, 'Octopus', 'Fist', and 'Half-and-Half'. There is also a cultivarnative to southern Sichuan, 'Muli' citron, which is intermediate between fingered and common citron.