Pomological and phenological characterization, genetic variability and genetic diversity of walnut (Juglans regia L.) genotypes in the Kodaikanal hills of Western ghats

The walnut (Juglans regia L.) is one of the most important temperate nut crops grown in India. The present investigation was conducted to study the variations available in the walnut population found in the Kodaikanal hills of Tamil Nadu.  Twelve selected walnut genotypes of seedling origin were evaluated for their phenological and pomological characters. The results revealed that among the genotypes, two of them (JR-7 and JR-11) were early in the first leafing (2nd - 3rd April). Genotypes JR-1, JR-3, JR-7, JR-8 and JR-12 were earlier in harvesting (15th – 20th October) than the other genotypes. High variation for nut and kernel characteristics was also observed among the genotypes evaluated. Genotypes, JR-5, JR-7, and JR-8 were identified as promising as they recorded higher kernel weight (6.00 g), nut weight (12.00 g) and kernel per cent (48%) than other genotypes. Diversity analysis (Mahalanobis D2 statistics method) resulted in a total of five clusters from the 12 walnut genotypes using 10 biometrical traits. More number of walnut genotypes were accommodated in cluster IV and cluster V with three genotypes each whereas cluster I, cluster II and cluster III comprised of two walnut genotypes each. Intra and inter cluster distance of five clusters was assessed and it varied from 1.29 to 10.82 and 7.66  to 21.36. Maximum intra cluster distance was recorded by cluster V (10.82) followed by cluster IV (3.14). Inter cluster distance was high between cluster III and cluster IV (21.36) followed by cluster IV and cluster V (20.55). Principal component analysis of 12 walnut genotypes with 10 quantitative traits resulted in the formation of three principal components viz. PC I, PC II and PC III with eigenvalues of 4.06, 1.84 and 1.44, respectively. These superior genotypes could be used for cultivation or as parents in future breedingprogrammes