UC Riverside

Key message

Engineered chromosomes 1BS and 1RS offer a new alternative in the development of hybrid systems in bread wheat and triticale. In the cytoplasmic male sterility system for hybrid wheat based on the cytoplasm of Triticum timopheevi fertility restoration is difficult, with few good restorer genes available. In the system based on the cytoplasms of Aegilops kotschyi, Ae. uniaristata and Ae. mutica, essentially all chromosomes 1B carry locus Rf ^multi that restores male fertility; male sterility manifests itself in wheats with the 1RS.1BL translocation where 1BS chromosome arm is missing. To generate male sterile wheats without the 1RS.1BL translocation, the 1BS arm was cytogenetically engineered to replace the segment with Rf ^multi with two short inserts of rye chromatin. Conversely, to enhance fertility restoration by doubling the number of restorers present for eventual use in wheat and triticale, a region of 1BS with Rf ^multi was inserted into 1RS. Alloplasmic wheats with Rf ^multi removed were completely male sterile; alloplasmic wheats with engineered 1RS carrying Rf ^multi and without normal 1B were male fertile. An exception to the ubiquitous presence of Rf ^multi is T. spelta var. duhamelianum; four accessions tested in this study gave inconsistent results but some did not restore male fertility. Engineered chromosomes 1BS and 1RS and chromosomes 1B of T. spelta offer a new alternative for practical application of a cytoplasmic male sterility system in the development of hybrid wheat and hexaploid triticale.