QTL and candidate gene mapping for polyphenolic composition in apple fruit.

Area of Science:

• Plant genetics
• Biochemistry
• Nutraceuticals

Background:

• Polyphenolic compounds like proanthocyanidins, anthocyanins, and flavonols in apples exhibit antioxidant properties beneficial for health.
• Investigating the genetic basis of these compounds in apples is crucial for understanding their biosynthesis and potential health impacts.

Purpose of the Study:

• To determine the genetic architecture controlling the biosynthesis of polyphenolic compounds in apple fruit.
• To identify specific genes influencing the concentration of antioxidants in apple varieties.

Main Methods:

• Quantification of 17 different polyphenolic compounds in apple progeny using ultra-high performance liquid chromatography.
• Construction of genetic maps for 'Royal Gala' and 'Braeburn' apple parents.
• In silico alignment of genetic maps with the apple whole genome sequence to identify co-localizing candidate genes.

Main Results:

• Seventy-nine quantitative trait loci (QTL) associated with 17 polyphenolic compounds were detected.
• Seven stable QTL clusters were identified across two harvest years, linked to flavanols, flavonols, anthocyanins, and hydroxycinnamic acids.
• Leucoanthocyanidin reductase (LAR1) and hydroxy cinnamate/quinate transferase (HCT/HQT) genes were found to co-locate with significant QTLs.

Conclusions:

• LAR1 and HCT/HQT are likely key genes influencing the concentration of specific polyphenolic compounds in apple fruit.
• These findings provide valuable allele-specific markers for marker-assisted selection in breeding programs for healthier apple varieties.