Variation and genetic parameters of fruit colour and polyphenol composition in an apple seedling population segregating for red leaf

Abstract

Red flesh colour is a relatively new target for apple breeding programmes and understanding genetic relationships between this trait and other fruit characters, including polyphenol compounds, is important for both breeders and marketers of new red flesh cultivars. In this study, fruit peel and flesh colours and concentrations of up to 20 individual fruit polyphenols within each tissue were examined in fruit harvested from a 14-family apple seedling population segregating for red and green leaf. Red leaf seedlings always produced red flesh fruit that varied from pale red to complete dark red cortical tissue (type 1 red flesh). Some (20 %) of green leaf seedlings also produced fruit with red flesh, albeit at low intensity (type 2 red flesh). Cyanidin 3-O-galactoside was the dominant anthocyanin in both fruit tissues, with concentrations being 1,900 times higher in the flesh and 2.5 times higher in the peel of fruit from red than from green leaf seedlings. Red leaf seedlings also had 59 % more flesh epicatechin and 17 % less total peel flavonols, but other polyphenols were not associated with leaf colour. Heritability estimates for red flesh colour, flesh cyanidin 3-O-galactoside, flesh and peel catechins were high in red leaf and low in green leaf seedlings. Conversely, estimates for red peel coverage and two peel anthocyanins were higher in green compared to those from red leaf seedlings. Other than these, heritability estimates were high only for dihydrochalcones and hydroxycinnamic acids from each tissue for both leaf colours but low for all other flesh and peel flavan-3-ols, procyanidins and most peel flavonols irrespective of leaf colour. Genetic correlations between polyphenol compounds varied considerably, but were broadly similar for red and green leaf seedlings. Genetic correlations were mostly moderate to high between compounds of the same metabolic group, but low between compounds from different groups. These results are discussed in relation to the genetic control of flesh colour and polyphenol accumulation in apple, as well as to implications for breeding red flesh apples with altered polyphenol composition.