Hybrid seedling inviability locus (HIs1 ) mapped on linkage group 4 of the Japanese flowering cherry, Cerasus x yedoensis ‘Somei-yoshino’
Cerasus × yedoensis ‘Somei-yoshino’ (2n = 16), one of the most popular cultivars of Japanese flowering cherry, is considered a hybrid between Cerasus spachiana and Cerasus speciosa. In the present study, we observed segregation of the trait for seedling growth in F 1 progenies of Somei-yoshino. In all three families crossed with ancestral wild species, C. spachiana, approximately half of the seedlings showed growth failure. To identify loci involved in seedling inviability, we constructed a genetic linkage map of Somei-yoshino. Both normal growth (N = 77) and growth failure seedlings (N = 101) of an F 1 progenies crossed between Somei-yoshino (CY) and C. spachiana (E750) were used for map construction. In accordance to pseudo-testcross strategy, female (CY) and male (E750) linkage maps were constructed. The CY map consists of eight linkage groups with 59 simple sequence repeat (SSR) and 17 amplified fragment length polymorphism (AFLP) markers. The map length is 574.9 cM. In contrast, the E750 map reached 196.8 cM and included 17 SSRs. Subsequently, we explored positions of loci associated to seedling inviability along with linkage maps. Results of segregation distortion of markers, association analysis, and interval mapping consistently showed that an inviability gene was located between two SSR markers, EMPaS13 and BPPCT005 in the fourth linkage group (LG4) of the Somei-yoshino map with 99.6 % explanations for the inviability trait but not present in LG4 of the E750 map. From the genotypes and expressions of seedling inviability, we named the locus Hybrid Inviability of seedlings 1 (HIs1). Finally, HIs1 was mapped to LG4 as Mendelian trait loci and was completely linked with an SSR, EMPaS13. Although the mechanisms of seedling inviability cannot be explained by only one locus model of HIs1, one of the candidate genes involved in hybrid incompatibility between Somei-yoshino and C. spachiana is certainly located on LG4 of the CY map.
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