Development and characterization of interspecific hybrids between Oryza sativa and O. latifolia by in situ hybridization

_{Oryza sativa} and _{O. latifolia} belong to the AA and CCDD genomes of _Oryza, respectively. In this study, interspecific hybrids of these species were obtained using the embryo rescue technique. Hybrid panicle traits, such as long awns, small grain, exoteric large purple stigma, grain shattering and dispersed panicles, resemble that of the paternal parent, _{O. latifolia}, whereas there is obvious heterosis in such respects as plant height, tillering ability and vegetative vigor. Chromosome pairing and the genomic components of the hybrid were subsequently investigated using genomic _{in situ} hybridization (GISH) and fluorescent _{in situ} hybridization (FISH) analysis. Based on the mitotic metaphase chromosome numbers of the root tips investigated, the hybrid is a triploid with 36 chromosomes. The genomic constitution of the hybrid is ACD. In the meiotic metaphase I of the hybrid pollen mother cell, poor chromosome pairing was identified and most of the chromosomes were univalent, which resulted in complete male sterility in the hybrid. Supported by the National Natural Science Foundation of China (Grant Nos. 30771210, 30500317 and 30600345) and National Basic Research Program of China (Grant No. 2006CB101701)