Abstract
The common fig (Ficus carica L.) has a gynodioecious breeding system, and its sex phenotype is an important trait for breeding because only female plant fruits are edible. During breeding to select for female plants, we analyzed the FcRAN1 genotype, which is strongly associated with the sex phenotype. In 12 F1 populations derived from 13 cross combinations, the FcRAN1 genotype segregation ratio was 1:1, whereas the M119-226 × H238-107 hybridization resulted in an extremely male-biased segregation ratio (178:7 = male:female). This finding suggests that the segregation distortion was caused by some genetic factor(s). A whole-genome resequencing of breeding parents (paternal and maternal lines) identified 9,061 high-impact SNPs in the parents. A genome-wide linkage analysis exploring the gene(s) responsible for the distortion revealed 194 high-impact SNPs specific to Caprifig6085 (i.e., seed parent ancestor) and 215 high-impact SNPs specific to H238-107 (i.e., pollen parent) in 201 annotated genes. A comparison between the annotated genes and the genes required for normal embryo or gametophyte development and function identified several candidate genes possibly responsible for the segregation distortion. This is the first report describing segregation distortion in F. carica.
Highlights
The import frequency of alleles into gametes often varies in the progeny population or a specific gene combination causes sterility, resulting in a segregation ratio that is inconsistent with Mendelian inheritance
In 12 of the 13 cross combinations, the segregation ratio of the male (G/A) and female (G/G) genotypes of FcRAN1 was. It is unclear whether the observed segregation distortion is caused by gametophytic lethality, embryonic lethality, or specific genetic events
In this study, a genome-wide linkage analysis (GWLA) was performed assuming that the causative factor is located on the chromosomes of either the seed parent (M119-226) or the pollen parent (H238107) of the population with distorted segregation
Summary
The import frequency of alleles into gametes often varies in the progeny population or a specific gene combination causes sterility, resulting in a segregation ratio that is inconsistent with Mendelian inheritance (i.e., segregation distortion). Segregation distortion is thought to have diverse causes, some of which involve gametophytic lethality, embryonic lethality, or cross-incompatibility (Lashermes et al, 2001; Candela et al, 2011) or are related to (selfish). Segregation Distortion in F. carica genetic elements that can enhance their own transmission (Dawkins, 1976; Werren et al, 1988).
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