Dissection of a major QTL qhir1 conferring maternal haploid induction ability in maize

Vijay Chaikam,Luis Antonio Lopez,Sudha K Nair,Willem Molenaar,Prasanna M Boddupalli,Albrecht E Melchinger,Leocadio Martinez

doi:10.1007/s00122-017-2873-9

Abstract

Key messageAmong the qhir11 and qhir12 sub-regions of a major QTL qhir1, only qhir11 has significant effect on maternal haploid induction, segregation distortion and kernel abortion.In vivo haploid induction in maize can be triggered in high frequencies by pollination with special genetic stocks called haploid inducers. Several genetic studies with segregating populations from non-inducer x inducer crosses identified a major QTL, qhir1, on chromosome 1.04 contributing to in vivo haploid induction. A recent Genome Wide Association Study using 51 inducers and 1482 non-inducers also identified two sub-regions within the qhir1 QTL region, named qhir11 and qhir12; qhir12 was proposed to be mandatory for haploid induction because the haplotype of qhir11 was also present in some non-inducers and putative candidate genes coding for DNA and amino acid binding proteins were identified in the qhir12 region. To characterize the effects of each sub-region of qhir1 on haploid induction rate, F2 recombinants segregating for one of the sub-regions and fixed for the other were identified in a cross between CML269 (non-inducer) and a tropicalized haploid inducer TAIL8. To quantify the haploid induction effects of qhir11 and qhir12, selfed progenies of recombinants between these sub-regions were genotyped. F3 plants homozygous for qhir11 and/or qhir12 were identified, and crossed to a ligueless tester to determine their haploid induction rates. The study revealed that only the qhir11 sub-region has a significant effect on haploid induction ability, besides causing significant segregation distortion and kernel abortion, traits that are strongly associated with maternal haploid induction. The results presented in this study can guide fine mapping efforts of qhir1 and in developing new inducers efficiently using marker assisted selection.

Highlights

Large-scale production and utilization of doubled haploid (DH) lines has become common practice in maize breeding programs during the last decade owing to the associated acceleration and cost reduction in development of inbred lines and deployment of hybrid varieties (Melchinger et al 2013)
A total of 475 recombinants in the F2 generation falling into different genotype classes were identified between qhir11 and qhir12 based on the segregation analysis of 7154 F 2 seeds (Table 1)
No recombination was observed between the two sub-regions in most of the F2 seeds (93.4%), which had the same genotype as the F1 cross or the parent lines

Summary

Introduction

Large-scale production and utilization of doubled haploid (DH) lines has become common practice in maize breeding programs during the last decade owing to the associated acceleration and cost reduction in development of inbred lines and deployment of hybrid varieties (Melchinger et al 2013). The major QTL qhir on chromosome 1.04 was the same as reported in the previous studies and explained 66% of the genotypic variance. Less pronounced than the effect of qhir was the effect of the second major QTL found by Prigge et al (2012b), qhir, which maps to chromosome 9 and explained only 20% of the genotypic variance. All these linkage mapping studies resulted in large support intervals for the detected QTL

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