In Vivo Haploid Induction in Maize: Comparison of Different Testing Regimes for Measuring Haploid Induction Rates

The doubled-haploid (DH) technology, based on in vivo induction of haploid seeds by pollen from inducer genotypes, has become routine in maize (Zea mays L.) breeding. De novo and maintenance breeding of inducers requires measuring the haploid induction rate (HIR) of numerous plants. We compared five testing regimes in combination with three inducers to find the best method for estimating HIR by discrimination of haploid (H) and crossing (C) seeds or plants with low false discovery rates (FDRs) and false negative rates (FNRs) in two experiments. Three testing regimes were based on tester genotypes LGT, GLT, and UFT equipped with the liguleless (lg2), glossy (gl), and herbicide-resistance (uf) gene, respectively. One testing regime used classification of H and C seeds in crosses with a high-oil tester (HOT). Embryo coloration as a result of the R1-nj marker gene was used as another testing regime. Flow cytometry analysis or phenotyping of adult plants served as gold standard classification (GSC). With HOT, H and C seeds were not clearly distinguishable because of considerable overlapping of their oil content (OC) distribution. Estimates of HIR from LGT and UFT generally agreed well with HIR from GSC and showed acceptable FDR and FNR. The HIR determined with GLT showed a high Matthew correlation with the GSC but lower estimates as a result of higher FNR. The HIR estimated with the R1-nj marker deviated considerably from HIR of GSC and had high FDR and FNR. Thus, we recommend LGT for determining HIR, but testing regimes UFT and HOT should be revisited.