Kiwifruit (Actinidia chinensis Planchon), one of the most recently domesticated specialty fruit crops, is currently grown commercially worldwide. The genus Actinidia (2n=2x=58 chromosomes) comprises 54 species and 75 taxa in total, and most of these species occur naturally in China. Most commercial cultivars were developed from a narrow pool of Actinidia chinensis germplasm, suffering from narrow genetic diversity and limited genetic and genomic information for cultivar improvement.  

ZHANG Qiong, supervised by Prof. HUANG Hongwen, from Wuhan Botanical Garden, presented high-density kiwifruit genetic maps using an interspecific F1 cross between Actinidia rufa ‘MT570001’ and A. chinensis ‘Guihai No4’. The A. rufa (maternal) map contained 2,426 single-nucleotide polymorphism (SNP) markers with 29 linkage groups (LGs) spanning over 2,651 cM, while, the A. chinensis (paternal) map with 4,214 SNP markers in 29 LGs spanning 3,142 cM. Using these maps, 440 unmapped scaffolds from the kiwifruit reference genome were anchored to chromosomes. The high-density genetic maps are beneficial for kiwifruit breeding programmes and improving the kiwifruit draft genome assembly.  

As a functionally dioecious plant, Kiwifruit has unique challenges for breeding and production. Three sex specific simple sequence repeats (SSR) markers that can accurately distinguish male and female kiwifruit were identified, which could be utilized in kiwifruit breeding and commercial production for marker-assisted selection for sex. By locating the three SSR markers in 1-2 Mb on chromosome 25, the sex determination region (SDR) in kiwifruit was narrowed to a 1 Mb region.  

Results entitled “High-density interspecific geneticmapsofkiwifruitand the identification ofsex-specific markers” were published on DNA Research. This project was supported by the National Natural Science Foundation of China.  This project was supported by the National Natural Science Foundation of China and Wuhan Applied Basic Research Project. 

High-density kiwifruit genetic map of A. chinensis (Image by ZHANG Qiong) 

Collinearity between the A. rufa and A. chinensis genetic maps (Image by ZHANG Qiong)