Haploid plants carrying a sodium azide-induced mutation (fdr1) produce fertile pollen grains due to first division restitution (FDR) in maize (Zea mays L.)

Abstract

We induced a fdr1 mutation in maize which makes haploid plants male fertile due to first division restitution; the optimum sodium azide treatment on maize kernels has been identified. Sodium azide mutagenesis experiments were performed on haploid and diploid maize plants. Kernels with haploid embryos of maize inbred line B55 were induced by pollinating with RWS pollen. These kernels were treated with 0.2, 0.5, or 1.0 mM sodium azide solution for 2 h. The 0.5 mM solution was optimal for inducing numerous albino sectors on the treated plants without significant damage. Kernels of a maize hybrid, Oh43 × B55, were treated with sodium azide solutions at concentrations of 1.5, 2.0, 2.5, and 3.0 mM. Haploids were generated by pollinating RWS pollen. The highest rate of chlorophyll mutations in seedlings (15.3 % [13/85]) was recorded with the 2.5 mM concentration. A mutated haploid plant (PP1-50) with higher pollen fertility was isolated during the experiments. This haploid plant produced four kernels on the ear after selfing. These kernels were germinated and produced ears with full seed set after selfing. The haploid plants induced from PP1-50 diploids also exhibited high pollen fertility. In situ hybridization studies showed that meiocytes in PP1-50 haploid anthers underwent first division restitution at a rate of 48 % and produced equally divided dyads. We designated the genetic factor responsible for this high pollen fertility as fdr1. PP1-50 haploid ears exhibited high levels of sterility, as seen for regular haploids. Diploid PP1-50 meiocytes in the anther underwent normal meiosis, and all selfed progenies were normal diploids. We concluded that the fdr1 phenotype is only expressed in the anthers of haploid plants and not in the anthers of diploid plants.

Novel technologies in doubled haploid line development

“…This genotype is called MiMe and transfers meiosis into mitosis. Sugihara et al (2013) induced a first division restitution (fdr1) mutant by sodium azide treatment. fdr1 haploids restore haploid male fertility attributable to first division restitution and produce diploid kernels.…”

QTL mapping for haploid male fertility by a segregation distortion method and fine mapping of a key QTL qhmf4 in maize

“…However, colchicine is a costly and toxic agent and the related treatment is labor intensive (Häntzschel et al 2010). Nitrous oxide gas (Kitamura et al 2009) is another genome doubling agent, but its effect on genome doubling is strongly influenced by genotype (Sugihara et al 2013).…”

“…Spontaneous genome doubling has been reported in maize for a long time (Chase 1952;Geiger et al 2006;Geiger and Schönleben 2011;Kleiber et al 2012;Sugihara et al 2013;Wu et al 2014).…”

“…Mutagenesis is another way to improve HMF. Sugihara et al (2013) reported a sodium azide-induced maize mutation, first division restitution 1 (fdr1), which has a high spontaneous genome doubling rate in both tassel branches and ovules. The mechanism of spontaneous genome doubling is still unclear and may be due to somatic cell fusion, endoreduplication, endomitosis or other mechanisms (Jensen 1974;Testillano et al 2004;Vanous 2011).…”

Impact of Spontaneous Haploid Genome Doubling in Maize Breeding

“…While these diploid-like phenotypes have been reported at various levels in global germplasm pools, little is known about the underlying genetic mechanism. Furthermore, a chemically induced mutation of the FIRST DIVISION RESTITUTION 1 (ZmFDR1) gene has resulted in first division restitution during meiosis within the male inflorescence [37]. This indicates that it is biologically possible to also have late-stage SHGD occurring as a mechanism within some of the lines reported to possess SHGD.…”