New Insights into the Genetics of Haploid Male Fertility in Maize

Doubled haploid (DH) lines have become widely used in maize (Zea mays L.) breeding. Haploid genome doubling is an important step in developing DH lines. The low rate of spontaneous genome doubling, which causes low haploid male fertility (HMF), seriously limits the largescale application of DH breeding without colchicine treatment. Our objective was to gain new insights into the genetics controlling HMF to improve the rate of HMF in DH breeding procedures. Haploid populations of 20 inbreds and their 31 single crosses derived from Chinese elite maize germplasm were screened for four traits related to HMF: anther emergence rate, pollen production rate, anther emergence score, and pollen production score. Haploid male fertility was compared between single crosses and their parents. Genotype effects were significant (p < 0.01) for all traits among Chinese elite maize lines and their single crosses, and interactions between genotype and environment were also significant (p < 0.05) for anther performance. Heritabilities ranged from 0.68 to 0.91 for these four traits. Haploid male fertility was controlled by additive effects with two or more genes. Anther emergence score proved to be the best trait for describing HMF and is the most practical trait for breeders. We propose that the potential use of HMF in breeding programs could reduce the need for toxic and costly artificial doubling treatments.