Genetic dissection of haploid male fertility in maize (Zea mays L.)

Abstract

Haploid genome doubling is a key limiting step of haploid breeding in maize. Spontaneous restoration of haploid male fertility (HMF) provides a more promising method than the artificial doubling process. To reveal the genetic basis of HMF, haploids were obtained from the offspring of 285 F2:3 families, derived from the cross Zheng58 × K22. The F2:3 families were used as the female donor and Yu high inducer No. 1 (YHI‐1) as the male inducer line. The rates of HMF from each family line were evaluated at two field sites over two planting seasons. HMF displayed incomplete dominance. Transgressive segregation of haploids from F2:3 families was observed relative to haploids derived from the two parents of the mapping population. A total of nine quantitative trait loci (QTL) were detected, which were distributed on chromosomes 1, 3, 4, 7 and 8. Three major QTL, qHMF3b, qHMF7a and qHMF7b were detected in both locations, respectively. These QTL could be useful to predict the ability of spontaneous haploid genome doubling, and to accelerate the haploid breeding process by introgression or aggregation of those QTL.

Impact of Spontaneous Haploid Genome Doubling in Maize Breeding

“…Fifteen lines were identified as exhibiting high SHGD, and among those, 14 single nucleotide polymorphisms (SNPs) were identified as significantly contributing to HMF (Figure 2). One of these SNPs may correspond to qhmf2 identified in the study by Ren et al [23], as well as qHMF3c identified by Yang et al [38] on chromosome 3 (Figure 2).…”

“…Ren et al [23] were the first to report a mapping study for SHGD, where they mapped a large-effect QTL (qhmf4) based on segregation distortion to a region on chromosome 6 in a bi-parental population derived from Chinese germplasm ( Figure 2). Moreover, in Chinese germplasm, Yang et al [38] mapped nine QTL in total ( Figure 2), one of which was located in bin 3.05 on chromosome 3 near qhmf2 described by Ren et al [23], and three QTL in bins 7.01 and 7.02 flanked a significant SNP on chromosome 7 ( Figure 2) that was identified by Chaikam et al [34]. Using a similar approach to [23], Ren et al [21] mapped a large-effect QTL (qshgd1) to chromosome 5 in US-derived germplasm, and a small-effect QTL (qshgd2) to chromosome 6, which mapped to a different location than qhmf4 ( Figure 2).…”

“…Due to the genetic diversity of SHGD donors in the abovementioned mapping studies, and the quantitative nature of most alleles, introgression of SHGD into a breeding program could be quite challenging. At least four QTL on chromosomes 3, 5, 6, and 10 have been identified by QTL mapping studies [21][22][23]38] and may be useful to increase SHGD ability in elite germplasm. The single large-effect locus on chromosome 5 identified by Ren et al and Trampe et al [21,22] should simplify introgression into elite germplasm by established MABC procedures.…”

“…There appear to be different mechanisms responsible for SHGD in maize, and their quantitative nature makes utilization difficult [19,33,34,38]. However, utilization of the SHGD systems from Ren et al [23], or Ren et al and Trampe et al [21,22], would be much simpler because they are based on a single locus with large effect.…”

“…Multiple approaches for introgression can be taken, depending on the desired level of recurrent parent genome (RPG) to be recovered and number of genes or QTL controlling the chosen mechanism of SHGD. Inheritance of SHGD is mediated both by single large-effect QTL [21][22][23] and multiple small-effect QTL [19,33,34,38]. The methods used to introgress SHGD into elite germplasm depend on the SHGD source and its underlying genetic mechanism.…”