First FISH-based physical mapping of Zea mays loci associated with haploid induction and anthocyanin biosynthesis reveals conserved chromosome loci and supports an integrated cytogenomics ideogram

Haploid induction is a key step to obtain Zea mays doubled-haploids, which are homozygous lines in breeding programs. Genes are related to haploid induction, as mtl and dmp , and to phenotypic screening based on anthocyanin biosynthesis, as r1-nj and b1 . Despite their relevance, the cytogenetics mapping of these genes is unpublished. Using interphases and metaphases, we aimed to determine the number of detectable loci, map these genes and evaluate their potential as cytomarkers, providing a revised Z. mays ideogram. Locus-specific FISH signals were detected in interphase nuclei and metaphases from the haploid inducer ‘KHI’ and five distinct donor lines, indicating single loci under the resolution limits. mtl , b1 and dmp were, respectively, mapped on chromosome 1, 2 and 9 short arm, and r1-nj on chromosome 10 long arm. Conserved chromosome mapping was observed between ‘KHI’ and donor lines. An integrated ideogram was constructed by combining the physical positions of these loci with 18S rDNA and previously described chromosome-specific cytomarkers. For the first time, we mapped these genes using direct physical mapping in Z. mays . We integrate cytogenomics and other genomic data, contributing to a better understanding of the genome organization and supporting applications in Z. mays breeding programs.