The D-genome plays a critical role in the formation of haploid Aegilops tauschii through Imperata cylindrica mediated uniparental chromosome elimination

Abstract

Doubled haploid (DH) breeding eventually offers unique advantages for rapid genetic improvement of wheat in a single generation by achieving absolute homozygosity and enhanced selection efficiency. A new perennial invasive weed i.e., Imperata cylindrica has already proved its importance in haploid wheat induction through Imperata-mediated chromosome elimination process. Whereas, cytological evidences and the actual mechanism of haploid induction through chromosome elimination in wheat x I. cylindrica hybrids are well known, but which genome(s) of wheat (AA/BB/DD) are actually involved in such haploid formation has remained elusive. Therefore, in order to identify the genome-specific triggering of Imperata-mediated chromosome elimination in development of wheat haploids, 11 wheat genotypes including Ae. tauschii and D-genome chromosome substitution lines of the durum wheat variety ‘Langdon’ were crossed with I. cylindrica and examined with the prime aim of producing haploids of Ae. tauschii. The crosses suggest that only bread wheat, Ae. tauschii and Triticale (containing D genome) were successful to develop haploid plants through chromosome elimination process. Higher frequencies of embryo formation were obtained primarily in substitution lines with chromosomes 7D. The detailed anatomical and cytological analyses suggest that : (i) genome/genotypic specificity plays a key role in haploid induction through Imperata-mediated chromosome elimination process, (ii) D-genome triggers the chromosome elimination and haploid production in wheat x Imperata, (iii) some D-genome chromosomes (primarily 7D) substituted lines in wheat genetic background may enhance crossability with Imperata in the formation of haploid wheat. To the best of our knowledge, this is the first report of haploid induction in Ae. tauschii.