In situ hybridization mapping of genes in Hordeum vulgare L.

Linkage maps of barley (Hordeum vulgare L.) containing genomic and cDNA sequences and functional genes have been constructed which cover a large genetic distance throughout the entire genome. It was decided to physically locate three genes from the barley linkage map to sites on chromosomes within the barley genome. In situ hybridization (ISH) with biotin-labeied DNA probes was used to determine the physical chromosome location of the genes for nitrate reductase, carboxypeptidase, and ol-amylase within the barley genome. The results indicated all of the genes studied hybridized to barley chromosomes 5H and 6H, and that the gene order on the physical map was similar to that observed on the genetic map. The major difference between the genetic map location of nitrate reductase and carboxypeptidase on chromosome 5H was the locations observed for each gene on the 5H short and long arms. The hybridization site of nitrate reductase on the short and long arms of chromosome 5H and the hybridization site for carboxypeptidase on the short arm of 5H was not observed on any genetic map. However, these sites were observed by ISH in the same location on different cultivars. The additional hybridization sites are probably due to the presence of silenced homologous sequences, or to unrelated sequences that show considerable homology. The nitrate reductase hybridization sites were also detected on the satellite, and the short and long arms of chromosome 6H.