IN-SITU HYBRIDIZATION MAPPING OF GENES IN HORDEUM-VULGARE L

Linkage maps of barley (Hordeum vulgare L.) containing genomic and cDN A sequences and functional genes have been constructed which cover a l arge 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 chromoso me 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 ge netic map. The major difference between the genetic map location of ni trate reductase and carboxypeptidase on chromosome 5H was the location s observed for each gene on the 5H short and long arms. The hybridizat ion site of nitrate reductase on the short and long arms of chromosome 5H and the hybridization site for carboxypeptidase on the short arm o f 5H was not observed on any genetic map. However, these sites were ob served by ISH in the same location on different cultivars. The additio nal hybridization sites are probably due to the presence of silenced h omologous 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.