Genetic variability studies for various morphological and quality traits in apple

Abstract

The present investigation was carried out to study the genetic variability among 120 apple cultivars for qualitative and quantitative traits. The apple cultivars showed a considerable genetic diversity with respect to qualitative and quantitative characters. Spreading type of growth habit was found in 84.16% of cultivars while 55% cultivars showed mixed bearing habit, i.e. on both shoots and spurs. Flower traits like color at balloon stage, position of anthers with respect to stigma and arrangement of petals varied among the apple cultivars. The highest average fruit weight (340.10 g) was recorded in Maharaji (White Dotted Red), while the lowest fruit weight of 1.30g was recorded in CITH-A-MB-03. Fruit firmness ranged from 44.59 RI in Tydeman’s Early Worcester to 91.70 RI in M. simcoe and TSS ranged from 9.50oB in Winter Commercial to 28.80oB in CITH-A-MB-01. With respect to fruit colour, “L” values ranged from 22.05 (CITH-A-MB-03) to 76.55 (Anannas Retrine) and 55 cultivars were found to possess light colour with ‘L’ values less than 50. Negative “a” values were recorded in 19 apple cultivars and all the green cultivars with negative ‘a’ values had higher L*, b* and hue values. The cluster analysis grouped 120 genotypes into five distant clusters at 0.70 average distances. Cluster I included three genotypes (Maharaji, Kirkitchoo, EC-239451), whereas maximum number of genotypes (45) were represented by Cluster II and cluster IV, comprising six wild apple cultivars. Correlation studies revealed that fruit weight was positively correlated with firmness but showed negative correlation with TSS where as firmness showed positive correlation with fruit weight and TSS. Principal component analysis (PCA) revealed the variability contribution of PC1, PC2 and PC3 to be 46, 35 and 18%, respectively, with PC1 mainly represented by fruit weight and firmness, PC2 by firmness and TSS and PC3 by fruit weight and TSS. The PCA and clustering analysis in this study indicated a high level of diversity in the apple genotypes.