Identification and classification of subspecies of Asian cultivated rice and their hybrids

Having reviewed the major classification systems proposed by various scholars across the world, it is found that Indica and japonica under O. sativa L. are two major directions thoroughly differentiated from the Asian cultivated rice, forming the framework of the classification structure. A system with Indica and japonica as the only two subspecies is therefore reiterated. There are various ways to determine the Indica-japonica identity of hybrid rice, but the "combined morphological trait index" (CMT index) method is more efficient and easier to handle, although the Isozyme analysis, molecular marker analysis and grain quality assay methods are also feasible.