Apple (malus domestica borkh) is an economically important fruit crop worldwide. Improvement for fruit quality and development of new varieties with high-quality are becoming critical for Chinese apple industry.

Prof. HAN Yuepeng and his Ph.D. student ZHANG Qiong from the Molecular Breeding of Fruit Trees Research Group at Wuhan Botanical Garden used an F1 population derived from a cross between ‘Jonathan’ and ‘Golden Delicious’ to construct linkage map and identify QTLs for sugar and acid contents in apple. Firstly, genetic diversity in 29 Malus was assessed using a set of 19 single-locus simple sequence repeat (SSR) markers distributed across all 17 linkage groups of the apple genome. The results demonstrated that great divergence was detected between ‘Golden Delicious’ and ‘Jonathan’, suggesting their F1 progenies are suitable for construction of genetic linkage map. Scientists characterized the distribution and density of microsatellites in apple genomic DNA sequence. A set of 81 newly developed SSR markers together with previously reported SSRs were subjected to construct genetic linkage maps of apple using the F1 population as mentioned above. The consensus linkage map spanned 1720.9cM with an average density of 7.3cM per marker. The contents of glucose, fructose, sucrose and malic acid of fruits were investigated at mature stage for ‘Jonathan’ , 'Golden Delicious’ and F1 progenies, and these phenotyping data were subjected to QTL analysis using interval mapping method. As a result, one QTL for malic acid content was detected on linkage group 8. The QTL explained ~ 16.9% of phenotypic variation, with a LOD score of 3.45. All these results not only provide new insights into molecular mechanism underlying sugar and acid contents in apple, but also could serve as molecular tools for genetic improvement of fruit quality traits.

This research was jointly funded by the National Basic Research Program (also called 973 Program), the National High-tech R&D Program (863 program) and the China National Science Foundation (NSFC). The relevant results were published in Plant Molecular Biology Reporter（SCI, Top30%）. The recent results entitled "Identification, characterization, and utilization of genome-wide simple sequence repeats to identify a QTL for acidity in apple” were published in BMC Genomics（SCI,Top30%）（DOI: 10.1186/1471-2164-13-537）.

Article link: http://www.springerlink.com/content/u1270p0467g8172k/

　　　　　http://www.biomedcentral.com/1471-2164/13/537/abstract