Variation of the crossability of durum wheat with maize

With the aim of examining crossability of durum wheat with maize, two sets of durum wheat genotypes and a set of D-genome chromosome substitution lines of the durum wheat variety 'Langdon' were crossed with maize, and followed by 2,4-dichlorophenoxyacetic acid (2,4-D) treatment in detached-tiller culture: In crosses of 25 durum wheat genotypes (breeding lines) with maize, percent frequencies of embryo formation increased from 1.4% to 2.8% by adding silver nitrate to the detached-tiller culture solution. In crosses of 32 durum wheat genotypes (advanced lines and varieties) with maize using the silver nitrate addition, frequencies of embryo formation ranged from 0.0% to 15.8%; seven genotypes showing more than 6.0% embryo formation frequency were related in their pedigrees. In crosses of a set of chromosome substitution lines with maize, higher frequencies of embryo formation were obtained in substitution lines with chromosomes 1D, 3D, 4D and 7D. These results suggest that 1) adding silver nitrate to the 2,4-D treatment increases overall frequency of embryo formation but is not effective enough to induce the development of seeds and embryos from all durum wheat genotypes, and 2) some D-genome chromosomes substituted in a durum wheat genetic background may enhance crossability with maize in combination with homoeologous chromosomes of durum wheat.