EFFECTS OF D-GENOME CHROMOSOMES ON CROSSABILITY OF HEXAPLOID TRITICALE (X TRITICOSECALE WITTMACK) WITH MAIZE

With the aim of producing polyhaploids of hexaploid triticale, 20 geno types from a CIMMYT breeding programme and eight D-genome chromosome s ubstitution lines of 'Rhino' were crossed with maize. In crosses betwe en 20 triticale genotypes and maize, 15 lines produced embryos. Freque ncies of embryo formation ranged from 0.0 to 5.4%, with an average of 1.1%. From a total of 200 pollinated spikes, 62 plants were regenerate d. Most regenerated plants were polyhaploids with 21 chromosomes, and few aneuhaploids with 22 chromosomes were found. In crosses of tritica le substitution lines with maize, all the lines produced embryos, whil e 'Rhino' produced no embryos at all. Higher frequencies of embryo for mation were obtained in substitution lines with chromosomes 2D and 4D. These results suggest that D-genome chromosomes in a triticale geneti c background have the effect of increasing the frequency of polyhaploi d production in triticale x maize crosses.