The construction of a high-density linkage map for identifying SNP markers that are tightly linked to a nuclear-recessive major gene for male sterility in Cryptomeria japonica D. Don.

Yoshinari Moriguchi,Asako Matsumoto,Tokuko Ujino-Ihara,Kentaro Uchiyama,Naoki Tani,Maki Saito,Yoshihiko Tsumura,Kenji Shinohara,Norihiro Futamura,Saneyoshi Ueno,Hideaki Taira

doi:10.1186/1471-2164-13-95

Abstract

BackgroundHigh-density linkage maps facilitate the mapping of target genes and the construction of partial linkage maps around target loci to develop markers for marker-assisted selection (MAS). MAS is quite challenging in conifers because of their large, complex, and poorly-characterized genomes. Our goal was to construct a high-density linkage map to facilitate the identification of markers that are tightly linked to a major recessive male-sterile gene (ms1) for MAS in C. japonica, a species that is important in Japanese afforestation but which causes serious social pollinosis problems.ResultsWe constructed a high-density saturated genetic linkage map for C. japonica using expressed sequence-derived co-dominant single nucleotide polymorphism (SNP) markers, most of which were genotyped using the GoldenGate genotyping assay. A total of 1261 markers were assigned to 11 linkage groups with an observed map length of 1405.2 cM and a mean distance between two adjacent markers of 1.1 cM; the number of linkage groups matched the basic chromosome number in C. japonica. Using this map, we located ms1 on the 9th linkage group and constructed a partial linkage map around the ms1 locus. This enabled us to identify a marker (hrmSNP970_sf) that is closely linked to the ms1 gene, being separated from it by only 0.5 cM.ConclusionsUsing the high-density map, we located the ms1 gene on the 9th linkage group and constructed a partial linkage map around the ms1 locus. The map distance between the ms1 gene and the tightly linked marker was only 0.5 cM. The identification of markers that are tightly linked to the ms1 gene will facilitate the early selection of male-sterile trees, which should expedite C. japonica breeding programs aimed at alleviating pollinosis problems without harming productivity.

Highlights

High-density linkage maps facilitate the mapping of target genes and the construction of partial linkage maps around target loci to develop markers for marker-assisted selection (MAS)
In 1992, a genetically male-sterile C. japonica tree whose sterility is determined by a major recessive gene was found in Toyama prefecture [13,14]; this gene is expected play an important role in breeding for reduced pollen dispersal
This paper reports a study in which a high-density linkage map for C. japonica was constructed and the mapping population was subjected to the GoldenGate genotyping assay

Summary

Introduction

High-density linkage maps facilitate the mapping of target genes and the construction of partial linkage maps around target loci to develop markers for marker-assisted selection (MAS). Our goal was to construct a highdensity linkage map to facilitate the identification of markers that are tightly linked to a major recessive male-sterile gene (ms1) for MAS in C. japonica, a species that is important in Japanese afforestation but which causes serious social pollinosis problems. Plus-trees that are heterozygous for ms have been identified by examining segregation data for the progeny arising from artificial crosses; such trees provide important breeding material for seed production while avoiding the problems associated with inbreeding depression. These methods are very time-, labour-, and space-intensive; as such, it would be extremely useful to develop a MAS-based method for selecting trees carrying the male-fertile gene

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