Creating a saturated reference map for the apple (Malus x domestica Borkh.) genome

Area of Science:

• Plant genetics
• Genomics
• Molecular biology

Background:

• High-quality genetic linkage maps are crucial for identifying and analyzing quantitative trait loci (QTLs).
• Effective maps require broad genome coverage, high marker density, and transferability across populations.
• Previous apple genetic maps lacked the desired comprehensiveness and marker types for advanced applications.

Purpose of the Study:

• To construct a high-density, high-quality genetic linkage map for apple (Malus).
• To facilitate the detection and analysis of quantitative traits in apple.
• To provide a transferable map for diverse apple populations and cultivars.

Main Methods:

• A segregating population was generated from a cross between 'Fiesta' and 'Discovery' apple cultivars.
• A total of 840 molecular markers were employed, including Amplified Fragment Length Polymorphisms (AFLPs), Random Amplified Polymorphic DNA (RAPDs), Simple Sequence Repeats (SSRs), and Sequence Characterized Amplified Regions (SCARs).
• The JoinMap software was used to construct two parental maps spanning 1,140 cM and 1,450 cM.

Main Results:

• The study successfully constructed an advanced apple genetic linkage map with significant genome coverage and marker density.
• The map incorporates a substantial number of codominant markers, such as SSRs, enhancing its utility for cross-population studies.
• The generated map is considered the most comprehensive to date for apple, providing a robust framework for future research.

Conclusions:

• The developed apple linkage map is a valuable resource for quantitative trait analysis in different genetic backgrounds.
• The high density and inclusion of transferable markers (SSRs) make this map ideal for saturation with dominant markers (AFLPs) in future projects.
• This map serves as a foundational tool for advancing genetic studies and breeding programs in Malus species.