Development of subtropically-adapted indeterminate gametophyte1 (ig1) gene-based paternal haploid inducer lines in...

The study successfully developed first of its kind subtropically adapted ig1 gene-based paternal haploid inducer lines in maize with HIR of 0.57-2.50% for rapid conversion of inbreds into its CMS versions. Maternal haploid inducer (HI) lines are extensively used for development of doubled haploid (DH) lines in maize (Zea mays L.), whereas paternal HI lines cause exchange of cytoplasm, therefore serving as an efficient tool for rapid conversion of inbreds to its cytoplasmic male sterile (CMS) version. However, indeterminate gametophyte1 (ig1) gene-based paternal HI lines are available for temperate climate. Here, effort has been made to develop the subtropically adapted paternal HI lines through marker-assisted selection of ig1 gene. Eight F₂ populations developed from cross between temperate inducer and elite subtropical lines were genotyped using ig1-specific functional InDel marker (MGU-IG1-Hopscotch). Severe segregation distortion (SD) for ig1 gene was observed in almost all F₂ populations. Male sterility was observed for majority of ig1/ig1 homozygotes, with only three out of eight F₂ populations contributed to fertile ig1/ig1 segregants. Mendelian ratio of 15 (fertile):1 (sterile) was observed in F₂ populations indicating the duplicate gene interaction between ig1 and other unknown gene in governing male sterility. Significant effect of 'genotype', 'environments', 'source of haploids' and 'genotype × environments' was observed for haploid induction rate (HIR). HIR of newly developed paternal HI lines ranged from 0.57 to 2.50% with the mean of 1.37% across environments. However, PHM8I as a source of haploids exhibited higher HIR (1.47%) compared to PVQ9I (1.28%). The HI lines were also found superior in agronomic performance and ease of maintenance. Here, we present the first successful attempt to develop subtropically-adapted ig1-based paternal HI lines.