Haploid induction by a maize cenh3 null mutant.

The production of haploids is an important first step in creating many new plant varieties. One approach used in Arabidopsis involves crossing plants expressing different forms of centromeric histone H3 (CENP-A/CENH3) and subsequent loss of genome with weaker centromeres. However, the method has been ineffective in crop plants. Here, we describe a greatly simplified method based on crossing maize lines that are heterozygous for a cenh3 null mutation. Crossing +/cenh3 to wild-type plants in both directions yielded haploid progeny. Genome elimination was determined by the cenh3 genotype of the gametophyte, suggesting that centromere failure is caused by CENH3 dilution during the postmeiotic cell divisions that precede gamete formation. The cenh3 haploid inducer works as a vigorous hybrid and can be transferred to other lines in a single cross, making it versatile for a variety of applications.