Diversity evaluation of fruit quality of apple (Malus × domestica Borkh.) germplasm through cluster and principal component analysis

Abstract

Thirty-six apple cultivars representing Malus × domestica Borkh. were evaluated for diversity in fruit quality. Colour traits ‘L’, ‘b’ and ‘Tint’ were positively correlated with TSS and fruit size. ‘a’ values showed negative correlation with TSS but was positively correlated with fruit firmness. ‘L’ values ranged from 32.66 (Well Spur) to 76.48 (Supermore Gold). Negative ‘a’ value was observed for Orange Val (−5.17), Snow Drift (−1.67) and Greensleeves (−7.70) indicating that these cultivars are green in colour at the time of harvesting. The ‘b’ values ranged from 6.86 (King Hacious) to 52.18 (Supermore Gold) indicating that these cultivars are yellow in colour and none blue. Positive ‘Tint’ value (2.36) was observed in Greensleeves cultivar and rest of the cultivars showed negative value. Fruit firmness ranged from 26.00 (Starkrimson Gold) to 90.85 RI (Top Red) and TSS from 11.80 °B (Razakwari) to 20.03 °B (Salvapobedetalian). Principal component analysis showed that first three components with Eigen values were able to explain more than 78% of total variation. PC1, PC2 and PC3 accounted for 37, 28 and 13% respectively, of the trait variability. Cluster analysis distinguished all the cultivars into five distinct groups/clusters and one cultivar Starkrimson Gold does not form the part of any cluster. Cluster analysis also revealed the importance of fruit weight and fruit firmness for grouping of apple cultivars while as TSS was found to have no significant role in grouping. The PCA and clustering analysis in this study indicated a high level of diversity in the apple cultivars. The present study is useful for identifying the apple cultivars with desirable fruit quality traits useful for commercialization and crop improvement through breeding.