Accelerated development of MTL and DMP gene-based subtropically-adapted maternal haploid inducer lines in maize using molecular breeding.

Doubled haploid (DH) technology has accelerated the development of inbreds in maize. Worldwide, breeding efforts have led to the development of diverse maternal haploid inducer (HI) lines adapted to temperate and tropical conditions. So far, no HI line adapted to subtropical conditions has been developed. Here, we crossed a temperate HI line used as a donor with a set of subtropical inbreds. The wild-type alleles of Matrilineal (MTL) and Domain membrane protein (DMP) genes were present among subtropically-adapted inbreds. While, the donor HI line possessed mutant mtl and dmp genes governing in vivo haploid induction in maize. Eight F populations were genotyped for MTL and DMP genes using gene-based markers, MTL_4InDel and DMP_SNP_TC, respectively. Severe segregation-distortion (SD) was observed for both mtl and dmp genes. Significant effect of 'inducer-type', 'environments', 'source of haploids', and 'inducer-type × source of haploids' was observed for haploid induction rate (HIR). HIR among mtlmtl-based inducers was 3.61%, while the same for dmpdmp was 0.52%. Significantly higher HIR (8.88%) was observed for mtlmtl/dmpdmp-based HI lines. Pusa-HI-MD5 and Pusa-HI-MD6 were the most promising HI lines with HIR of 10.61 and 11.11%, respectively. Among source-germplasm, 'Pusa Vivek QPM9 Improved' produced more haploids (5.38%) over 'Pusa HM8 Improved' (4.40%). Further, HIR was more during rainy season (HIR: 5.16%) over spring season (HIR: 4.62%). The newly developed HI lines possessed superior-agronomic traits over temperate donor. This is the first report of development of HI lines adapted to subtropical conditions.