Genotyping for male sterility (MS) and MS gene mapping with RAPD markers in citrus, especially with

Seedlings from Citrus species and cultivars show precocious flowering after autumn seed germination. HY16is a monoembryonic and male sterile hybrid-derived from a cross of ‘Hanayu’ (Citrus hanaju) × ‘Yuzu’ (Citrusjunos). ‘Kiyomi’ tangor (satsuma × ‘Trovita’), a male sterile and monoembryonic plant, was also used todetermine the male sterile genotype of grapefruit. Both seed parents generated seedlings with precociousflowering ability. Seeds were collected in November of 2006-2011 in Fukuoka, Japan, and allowed to germinatein a greenhouse (>10°C). Male sterile anthers were observed in hybrid seedlings from several crosses, i.e.,HY16 × grapefruit, (HY16 × grapefruit) × grapefruit, HY16 × ‘Ruby Blood’ orange, (HY16 × grapefruit) × ‘RubyBlood’ orange, HY16 × ‘Trovita’ orange, and ‘Kiyomi’ × grapefruit. On the basis of segregation analysis for MSin these progenies, and on the fact that HY16 and ‘Kiyomi’ did not have cytoplasmic restoration factor R forMS, male sterile genotype was estimated to be mS₁mS₁MS₂mS₂mS₃mS₃ (R-) for HY16, MS₁mS₁mS₂mS₂mS₃mS₃(R-) for ‘Kiyomi’ and mS₁mS₁MS₂MS₂MS₃mS₃ or MS₁mS₁MS₂MS₂mS₃mS₃ (R) for grapefruit with male fertileanthers. Here, MS is a recessive character; mS₁ and mS₂ are complementary genes with upper streamexpression of mS₂, and mS₃ is an epistatic gene to mS₁ and mS₂ genes. Male sterile seedlings appear whenmS₃ is recessive homozygous (mS₃mS₃) and either mS₂ or mS₁ is recessive homozygous (mS₂mS₂ or mS₁mS₁). Apopulation of 101 individuals from the cross of HY16 × grapefruit was chosen for mapping of Ms genes. Usingb