Development of high-oil maize haploid inducer with a novel phenotyping strategy

Doubled haploid (DH) technology is important in modern maize breeding. Haploid inducers determine the efficiency of both haploid induction and identification. It has taken decades to improve the efficiency, haploid induction rate (HIR), from the ∼2% of the ancestor haploid inducer, stock6, to the ∼10% of modern haploid inducers. Improvement of kernel oil content (KOC) would further enhance haploid identification efficiency. Using molecular marker-assisted selection, in combine with the number of haploids per ear as phenotypic criterion, we developed a new high-oil haploid inducer line, CHOI4, with a mean HIR of 15.8% and mean KOC of 11%. High KOC of CHOI4 can achieve a mean accuracy greater than 90% in identification of haploids of different backgrounds, with reduced false discovery rates and false negative rates in comparison with the previous high-oil haploid inducer line, CHOI3. Comparison of phenotypic selection strategies suggested that the number of haploids per ear can be used as a phenotyping criterion during haploid inducer line development. CHOI4 could further increase the efficiency of large-scale DH breeding programs with lower cost.