Construction Of High-density Interspecific Genetic Maps And Identification Of OTLs For Fruits In Kiwifruit

Domestication of wild kiwifruit was considered to be one of the most successful examples of plant domestication in the 20th century. Kiwifruit has been widely welcomed because of its high content of vitamin C. Dioecy and intraspecific polyploidy present great challenges in kiwifruit breeding and cultivar improvement. Selection based on molecular markers associated with traits of interest can enhance the selection efficiency and precision in plant breeding. In the present study, we constructed two linkage maps in an interspecific population and mapped several fruit traits of kiwifruit. The main results were highlighted as follows:(1) We present high-density RAD-seq-based genetic maps in a F1 cross between Actinidia rufa’MT570001’and Actinidia chinensis ’Guihai No4’. The A. rufa (maternal) map consists of 2,426 single-nucleotide polymorphism (SNP) markers with a total length of 2,651 cM in 29 linkage groups (LGs) corresponding to the 29 chromosomes. The A. chinensis (paternal) map consists of 4,214 SNP markers over 3,142 cM in 29 LGs.(2) A total of 49,067 SSR were identified and characterized in the genome sequences of kiwifruit. Dinucleotide repeats were the most abundant SSR, with the AG/TC motif accounting for 44.2% of all SSR in the genome. Sixty-one newly derived SSR, together with 49 previously available SSR, were integrated into linkage maps of an interspecific population. In addition, eleve sex linked SSR markers were mapped in the sex-related region on the LG25, suggesting that recombination is partially suppressed to maintain dioecy in kiwifruit.(3) Forty-four QTLs for 12 traits were detected in the maternal map, and the phenotypic variation explained by the QTLs ranged from 5.3% to 13.9%. Fifty-seven QTLs were identified in the paternal map and the phenotypic variation explained by the QTLs range from 5.9% to 12.2%.All the above results not only facilitate genetic study for Actinidia and provide new insights into molecular mechanism underlying dioeciey and fruit quality, but also serve as molecular tools for marker-assisted selection in kiwifruit.