Genetic mapping of the gene for brittle rachis in a Triticum aestivum—Aegilops triuncialis introgression line

Abstract

Aegilops triuncialis L. (2n = 4x = 28, genome formula UUCC) has been used to obtain one of the “Arsenal collection”, the distant hybridization of Triticum aestivum L. The introgression line 124/00i, which was derived from the cross of T. aestivum ‘Rodina' with γ-irradiated pollen of an accession of Ae. triuncialis. However, undesirable genes can be incorporated into the cultivated varieties from Ae. triuncialis. The spikes of Ae. triuncialis disarticulate from stems at a single node at the bottom of the spikes. It was defined as a synaptospermic diaspore. However, the spike of 124/00i unexpectedly disarticulate below each spikelet showing wedge type of disarticulation. The brittle rachis gene Br 124 (B rittle r achis of 124 /00 i ) of 124/00i was allelic to Br2 located on the short arm of chromosome 3A. From the microsatellite mapping, the Br 124 gene was bracketed by Xbarc19 (20.3 cM) and Xgwm779.1(14.3 cM) on the short arm of chromosome 3A. The present study suggested that the dominant mutation from synaptospermic diaspore to wedge type disarticulation occurred in the gamete of Ae. triuncialis when Ae. triuncialis pollen was treated with γ-irradiation.