Khush is adjunct professor at UC Davis. He obtained his PhD at UC Davis in 1960. After serving as assistant geneticist at the same university for seven years, he joined the International Rice Research Institute in the Philippines as plant breeder. He retired as principal plant breeder and head of the division of plant breeding, genetics and biotechnology in 2002. His honours include 14 honoris causa doctorates and several awards including the Japan Prize, World Food Prize, Rank Prize, Wolf Prize, Golden Sickle Award, Mahathir Science Award and the Padma Shri Award by the President of India. He is a member of 9 science academies including Indian National Science Academy, Chinese Academy of Sciences, Russian Academy of Agricultural Sciences, the Royal Society and the US National Academy of Sciences.