Oligoclonal interspecific origin of 'North Indian' and 'Chinese' sugarcanes.

Sugarcanes consist of several groups of complex polyploid forms. The origin of 'North Indian' and 'Chinese' sugarcanes (referred to as S. barberi and S. sinense) was investigated using genomic in-situ hybridization (GISH), detection of species-specific repeated sequences and RFLP. GISH proved their interspecific hybrid origin. Together with the distribution of species-specific repeated sequences and earlier RFLP data, the results show that both taxa are derived from interspecific hybridization between S. officinarum and S. spontaneum and that no other genus has been directly involved. RFLP indicates that the clones are clustered into a few groups, each derived from a single interspecific hybrid that has subsequently undergone a few somatic mutations. These groups correspond quite well with those already defined based on morphological characters and chromosome numbers. However, the calculated genetic similarities do not support the existence of two distinct taxa. The 'North Indian' and 'Chinese' sugarcanes represent a set of horticultural groups rather than established species.