Characterization of wide cross derivatives in rice <i>Oryza sativa</i> L. using genomic <i>in situ</i> hybridization (GISH)

Abstract

Interspecific crosses provide a bridge by which the gene pool of rice can be increased. Introduction of alien genes requires hybridization followed by meiotic pairing and recombination between the chromosomes of cultivated and wild species. Attempts have been made to visualize the genomic constitution of wide-cross derivatives. Genomic in situ hybridization was used to detect Oryza australiensis chromosomes and introgressed segment from O. australiensis into the Oryza sativa background. Genomic DNA from O. australiensis was labeled with biotin-14-dATP and hybridized to the homologous chromosomes in hybrids, back cross progenies, monosomic alien addition line (MAAL) and introgression line. The probe hybridization fluoresced green and non-labeled O. sativa chromosomes appeared red due to counterstaining with propidium iodide (PI). This differential painting of chromosomes unequivocally detected the O. australiensis chromatin introgressed into the O. sativa genome. The probe produced uniform labeling pattern over the entire length of all the O. australiensis chromosomes. Genomic in situ hybridization (GISH) detected 12 O. australiensis chromosomes in the hybrid, O. sativa x O. australiensis in BC1 progenies, and a single chromosome in MAAL. Small segment of O. australiensis was localized on the chromosome 12 of the introgression line. However, results showed that GISH is a powerful technique to be used as an aid in selecting segregating progenies.

Key words: Genomic in situ hybridization, wide hybrid, localizing introgression.