Wheat Mapping via Chromosome Deletion

According to standard banding nomenclature based on Chinese Spring wheat, the arms of the wheat chromosomes are divided into morphologically short (S) and long (L) arms. Arms are distinguished by a series of light (euchromatin) and dark (heterochromatin) staining areas produced by the C-banding procedure. The designation of chromosome bands for each arm begins at the centromere and proceeds distally. Landmark bands can divide a chromosome arm into two or more regions. The bands in each region are then numbered sequentially. Each chromosome has a distinct centromere and the heterochromatin bisected by the centromere is considered as two bands. These bands are band 1 in region 1. The C-band numbering is on the left of each chromosome.

The deletion breakpoints are labeled on the right of each chromosome. Each deletion is indicated by the chromosome arm (in this case 6AS, 6AL, etc.) and a sequential number. This tag is followed by the FL (fraction length) value, which indicates the percent of the chromosome arm present in each deletion chromosome. For example, deletion 6AS-4 has an FL value of 0.67, indicating that 67 % of the short arm of chromosome 6A remains (a 33 % deletion of the arm).

Thus, a marker can be allocated to a certain chromosome segment by its presence or absence in each of the deletion segments. The overlapping deletion stocks provide excellent tools for allocating RFLP probes to deletion bins.