Lysine is a limiting essential amino acid in rice. This study determined the variation in lysine content and evaluated the relationship between lysine and protein content in indica rice landraces of four provinces (Guangdong, Guangxi, Hunan, and Sichuan) in China by using the data (n = 654) collected from the Chinese Crop Germplasm Information System. Results showed that grain lysine content ranged from 0.25 % to 0.54 %, with 139 landraces having a grain lysine content of more than 0.40 %. Lysine content of protein ranged from 28.4 to 48.1 mg g...