Monosomics in Maize Induced by X-irradiation of the Pollen

Five plants of maize having monosomic microsporocytes were isolated from the X1 following crosses of zb4Pwwbr1 by irradiated pollen carrying Zb4PwrBr1. Three plants were hemizygous for all three recessive markers in chromosome 1. Since the marked region contains the centromere and all dominant markers genes from the pollen parent were deficient, it was concluded that chromosome 1 was missing. Root-tips of two of the three plants were in division and were monosomic. Two other plants with 19 chromosomes in the pollen mother cells were also found. One plant had 19 chromosomes in the root-tips; mitosis was not obtained in the other. These two plants were not hemizygous for all three recessives in chromosome 1, suggesting that a different chromosome had been lost.