Genotypic variations of ten Indian cultivars ofColocasia esculentavar.antiquoromSchott. evident by chromosomal and RAPD markers

Abstract

Detailed karyotype, genome size and RAPD marker analysis were employed to assess genetic diversity in Taro (Colocasia esculenta var antiquorom Schott.). Karyotype analysis revealed genotype specific chromosomal characteristics and structural alterations in chromosome with variations of ploidy from 2n = 2x = 28 (cv. Mothan, cv. Muktakeshi, cv. Sree Kiran, cv. Sree Pallavi, cv. Sunajhili) to 3n = 3x = 42 (cv. Banky, cv. DP-25, cv. Duradin, cv. H-3, cv. Telia) in the genome. Highly significant variations in the genomic length, volume and total form (TF) % were noted at variety level. Total genomic chromosome length varied from 46.96μm in cv. Sree Kiran to 100.49μm in cv. Duradin. Total genomic chromosome volume varied from 18.22μm3 in cv. Sunajhili to 38.22μm3 in cv. Duradin. Total form percentage was varied from 24.94% in cv. Sree Kiran to 39.04% in cv. H-3 confirming near metacentric to metacentric chromosomes in the karyotype. Significant variations in the 4C DNA content noted among the cultivars that ranged from 7.24 pg in cv. Sree Kiran to 18.24 pg in cv. Duradin; accordingly, genome size varied from ~7095 to 17875 Mbp. High genome size in all the triplod varieties with 3x = 42 chromosomes could be due to the presence of extra set of chromosomes in the genome or high amount of repetitive DNA. The variation in the genome size at the variety level might be attributed to loss or addition of highly repetitive sequences in the genome. Amplification of genomic DNA in 10 genotypes using Operon primers yielded 230 amplified DNA fragments, ranging in size from 200 to 2500bp out of which 79 bands were polymorphic. A total of 8 unique RAPD bands were observed among 10 taro genotypes that revealed primer wise polymorphism ranged from 16.66 to 47.36% with an average polymorphic percentage of 34.34%. Whereas, among the cultivars the polymorphic percentage varied from 3.70% between cv. DR-25 & cv. Duradin and cv. Telia & cv. H-3 to 41.94% between cv. Mothan & cv. Muktakeshi. Genetic similarity based on Jaccard’s coefficient varied from 0.54 to 0.96, indicating wide genetic variability among the varieties based on RAPD markers. Similarity measures and cluster analysis generally reflected the expected trends in relationships of diploid and triplod taro varieties. Dendrogram obtained from the genetic distances among the varieties could be useful for breeders to choose the diverse parents for breeding programme aimed at varietal improvement.