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 substit ution lines of the durum wheat variety 'Langdon' were crossed with mai ze, and followed by 2,4-dichlorophenoxyacetic acid (2,4-D) treatment i n detached-tiller culture: In crosses of 25 durum wheat genotypes (bre eding lines) with maize, percent frequencies of embryo formation incre ased from 1.4% to 2.8% by adding silver nitrate to the detached-tiller culture solution. In crosses of 32 durum wheat genotypes (advanced li nes and varieties) with maize using the silver nitrate addition, frequ encies of embryo formation ranged from 0.0% to 15.8%; seven genotypes showing more than 6.0% embryo formation frequency were related in thei r pedigrees. In crosses of a set of chromosome substitution lines with maize, higher frequencies of embryo formation were obtained in substi tution lines with chromosomes 1D, 3D, 4D and 7D. These results suggest that 1) adding silver nitrate to the 2,4-D treatment increases overal l frequency of embryo formation but is not effective enough to induce the development of seeds and embryos from all durum wheat genotypes, a nd 2) some D-genome chromosomes substituted in a durum wheat genetic b ackground may enhance crossability with maize in combination with homo eologous chromosomes of durum wheat.