The 1BL/1RS translocation decreases grain yield of spring wheat germplasm in low yield environments of north-eastern Australia

Wheat ( Triticum aestivum L.) lines containing the 1BL/1RS chromosome translocation yield up to 20% more than established wheat cultivars in some Queensland environments. However, 1BL/1RS germplasm possesses a quality defect known as 'sticky dough', which is incompatible with the high-speed dough-mixing processes used for bread production in Australia. Therefore, weinvestigated whether the 1BL/1RS translocation conveyed a yield advantage to locally adapted germplasm across a wide range of environments that was sufficient to justify attempting to overcome the 'sticky dough' defect either through plant breeding or by altering the mixing processes. Three sets of recombinant inbred lines (RILs) that segregated for the presence or absence of the 1BL/1RS translocation were developed from crosses between 1BL/1RS germplasm (Seri and Genaro) and established local cultivars (Hartog and Banks), and grown in 11 environments representing six sites across southern Queensland and northernNew South Wales and two years. The effect of the 1BL/1RS translocation on grain yield depended on environment and genetic background. In semi-dwarf genotypes of the Hartog/Seri and Hartog/Genaro crosses, the 1BL/1RS RILs had lower grain yield than the 1B RILs in the three lowest yielding environments. This effect was associated with changes in grain number per unit area, suggesting that the negative yield effect of the translocation is expressed before, or at, anthesis. In the higher yielding environments, the 1BL/1RS translocation conveyed a yield advantage in semi-dwarf genotypes of the Banks/Seri cross, but had no consistent effect on yield in semi-dwarf genotypes of the Hartog/Seri and Hartog/Genaro crosses. The 1BL/1RS translocation was also associated with decreased yield in the double-dwarf genotypes of the Hartog/Seri cross across all environments. We conclude that the 1BL/1RS translocation is not useful for local breeding programs, as it decreased yield among the more advanced, semi-dwarf germplasm in low-yielding environments that potentially represent up to 85% of the target population of environments, and had no consistent positive effect on yield in this germplasm in higher yielding environments.