Efficient production of haploid wheat (Triticum aestivum) through crosses between Japanese wheat and maize (Zea mays)

Four Japanese wheat varieties, three crossable and one non-crossable with Hordeum bulbosum, were pollinated with maize pollen of 5 genotypes. By the application of 2,4-dichlorophenoxyacetic acid after pollination, embryos kept developing on wheat plants until 14 days after pollination. The frequency of embryo formation was significantly different among the maize genotypes, varying from 18.0% to 31.9%, but not among the wheat varieties. By bagging spikes with flag leaves the frequency of embryo formation was increased by about 7%. Ten- to twelve-day-old embryos gave higher frequencies of plant formation (83.6%) than 14-day-old embryos(50.0%). All 6 regenerated plants investigated cytologically were found to be haploid. Twelve of the 14 colchicine-treated plants produced florets setting seeds. The overall efficiency of our procedure is considered to be higher than that reported by Laurie and Bennett (1988).