The medium defined by Gresshoff and Doy is developed for growth of haploid callus and plants of Arabidopsis thaliana cultured from the diploid anthers. The anthers were removed during the late prophase of meiosis, selecting a genotype favouring callus formation from dividing sporocytes on a high auxin - low kinetin concentration in a fully defined medium. Further differentiati-on was induced by transfer to a low auxin - high kinetin medium with a light-dark cycle. Haploid callus cultures of tomato, barley and Vitis vinifera have been cultured as well using this method.