Dissection of barley chromosome 4H in common wheat by the gametocidal system and cytological mapping of chromosome 4H with EST markers.

We used two gametocidal (Gc) chromosomes 2C and 3C(SAT) to dissect barley chromosome 4H added to common wheat. The Gc chromosome induced chromosomal structural rearrangements in the progeny of the 4H addition line of common wheat carrying the monosomic Gc chromosome. We conducted in situ hybridization to select plants carrying rearranged 4H chromosomes and characterized the rearranged chromosomes by sequential C-banding and in situ hybridization. We established 60 dissection lines of common wheat carrying single rearranged 4H chromosomes. The rearranged 4H chromosomes had either a deletion or a translocation or a complicated structural change. The breakpoints were distributed in the short arm, centromere and the long arm at a rough ratio of 2:2:1. We conducted PCR analysis using the dissection lines and 93 EST markers specific to chromosome 4H. Based on the PCR result, we constructed a cytological map of chromosome 4H with 18 regions separated by the breakpoints of the rearranged chromosomes. Thirty-seven markers were present in the short arm and 56 in the long arm, and about 70% of the markers were present in no more than the distal 25.6% and 43.1% regions of the short and long arms, respectively. It is noteworthy that nine of the short-arm markers and 13 of the long-arm markers existed in the small subtelomeric regions at both ends characterized by the HvT01 sequences. We reconstructed a genetic map using 38 of the 93 markers that was used to construct the cytological map of chromosome 4H. The order of the markers on the genetic map was almost the same as that on the cytological map. On the genetic map, no markers were available in the pericentromeric region, but on the cytological map, 14 markers were present in the proximal region, and one of the markers was in the centromeric region of the short arm.