Haploid oat plants produced by application of maize pollen to emasculated oat florets

Only six haploids in oat (Avena sativa L.) have been previously reported, five of spontaneous origin and one from anther culture. Our objective was to develop more efficient methods for producing oat haploids to use in selecting mutants, recovering aneuploids, and producing doubled-haploid lines for genetic and breeding studies. In a series of experiments, pollen from maize (Zea mays L.) was applied to previously emasculated oat florets. Twelve to 15 d later excised ovaries/caryopses, or embryos taken from them, were placed onto an amino acid-supplemented Murashige and Skoog medium containing 7% sucrose for embryo rescue. Recovered plantlets were potted in soil and grown to maturity. Root tips and meiotic tissues were sampled for cytological analyses. Overall, 14 haploid oat plants were recovered by embryo rescue following application of maize pollen to approximately 3300 emasculated oat florets. Root tip cells in each of the recovered plants had the oat haploid chromosome number of 21. Presumably these oat haploids originated from interspecies hybrid zygote formation followed by elimination of maize chromosomes during initial cell divisions, as has been described in haploid wheat (Triticum aestivum L.) formation in wheat X maize hybridizations. In the initial experiment, which involved combinations of various oat and maize genotypes, each of the four oat haploids recovered was from a different oat cultivar and each involved a different source of maize pollen; thus, indicating that the process is not genotype unique. Meiotic cells of the recovered haploid plants were characterized by aberrant chromosome behavior and numerous micronuclei, as expected in a haploid. Occasional seed were set on haploid plants and both euploid (2n) and aneuploid (2n-1 and 2n-2) progeny were obtained. The use of maize pollinations provides a new approach for obtaining haploid oat plants for genetic and breeding studies.