1RS1BL

1RS1BL is a chromosome configuration found in bread wheat that results from a wheat-rye translocation. In this structural rearrangement, the short arm of rye chromosome 1 (1RS) is attached to the long arm of wheat chromosome 1B (1BL), effectively replacing the wheat 1BS segment. This translocation is denoted as 1RS.1BL in some references, with variations in punctuation used in different naming systems.

Origin and prevalence: The 1RS arm used in wheat breeding most commonly derives from the rye species Secale cereale, with the Petkus (Petk) rye line historically serving as a major donor. The 1RS.1BL translocation became widely adopted in hexaploid bread wheat during the mid- to late 20th century and has since appeared in a large number of commercial cultivars around the world due to its disease resistance and agronomic advantages.

Genetic content and traits: The rye 1RS arm carries a cluster of disease-resistance genes that have been valuable for wheat improvement. Notably, Sr31 provides resistance to several stem rust races, Lr26 to leaf rust, and Pm8 to powdery mildew. These resistance genes contributed to enhanced disease management in areas where rust pressures are high. However, the rye segment also introduces rye-specific glutenin and gliadin components that can influence end-use quality.

Impact on quality and breeding considerations: The 1RS.1BL translocation can adversely affect certain bread-making properties, including dough strength and loaf volume, due to changes in gluten composition. As a result, breeders balance disease resistance with end-use quality, sometimes developing alternative lines or using marker-assisted strategies to manage the 1RS segment. Some programs have reduced or replaced 1RS in new varieties to optimize quality while retaining resistance through other sources.

See also: wheat-rye translocations, Sr31, Lr26, Pm8.