Genomic in situ hybridization（GISH）analysis on Oryza schweinfurthian with digoxigenin-labelled genomic DNA from O.sativa was used to study the relationship between the A genome of O.sativa and BC genome of O.schweinfurthian.Karyotype analysis was made based on the similar band patterns of the hybridization signal.The result showed that A genome of cultivated rice had higher homology with genome of African wild rice,including repetitive DNA sequence conserved between cultivated rice and African wild rice.