Article by Larry C.Y. Wong which appeared in Soh Aik Chin & Yong Hoi Sen (eds.) Food Security Malaysia, Kuala Lumpur: Akademi Sains Malaysia, 2009, pp. 55-67. This paper was presented at the Akademi of Sains Malaysia 2nd Series of ASM Biotechnology and Agriculture Forums: Food Security held at Universiti Malaya, Kuala Lumpur, 16 March 2007.