Actually, researchers from University of California, Riverside (UCR), Department of Botany and Plant Sciences, United States; and United States Department of Agriculture, Agricultural Research Service (USDA-ARS)
for the Chinese Citron Germplasm Project travelled around Yunnan and other provinces of China, observing both cultivated and wild citrons, collected information about germplasm, horticultural practices, and economic uses, as well as cuttings and seeds, which were used to establish a germplasm collection with 30 accessions in Jianshui, Yunnan Yunnan, China.
Xulan Huc and David Karpa found specimen ‘Ninger Giant’ citron, the fruit weights about 15 kg ,making it the largest known citrus fruit.