Phenotypic variation and estimation of genetic parameters to improve fruit quality in Tunisian pomegranate (Punica granatum L.) accessions

In order to improve fruit traits in a breeding programme, both genetic and environmental effects need to be evaluated. The partitioning of variance and genetic parameters for fruit quality traits were estimated in 28 accessions of Tunisian pomegranate by considering the effects of variety, clone, and year, and their interactions. The results showed that variety contributed most to the variance in fruit size and skin colour, while the largest variances in skin thickness, and aril and juice yields were associated with year. Clones differed in most traits, reflecting differences in their genetic background. Also, clone x year interactions were significant for all traits, indicating the influence of environment on the expression of attributes of pomegranate fruit. High heritability, along with genetic advances in fruit weight, skin colour, juice colour, and titratable acidity (TA) suggested that there were significant additive gene effects for such traits. Fruit weight and fruit diameter were unstable over years. Some clones ('Tounsi 6', 'Chelfi 1', and 'Chelfi 6') were considered to have high adaptability to favourable environmental conditions, while others ('Gabsi 3', and 'Zehri 6') behaved best under unfavourable conditions. In general, the genotypic correlations were lower in magnitude than the corresponding phenotypic correlations for all pairs of traits. Interestingly, the positive genotypic correlations between skin colour and TA, and between aril and juice yields, confirmed the possibility of selecting clones with red-coloured and acid fruit, and others with high aril and juice yields. Our results showed that there are ample opportunities to improve several fruit traits in pomegranate to adapt to different environmental conditions.