Genetic diversity analysis of greater yam (Dioscorea alata) landraces in Kerala

Abstract

Yams belonging to Dioscoreaceae family are important climate resilient food security crops and widely cultivated in India, one of its center of origin, and in Africa. In India, greater yam (Dioscorea alata L.) is one of the major cultivated yam species andit provides a very good source of dietary carbohydrates in regions of tropic and subtropics. This research work attempts molecular, morphological and biochemical characterization of 45 landraces collected from different districts of Kerala for greater understanding of the distribution and extent of genetic variation present within the Dioscorea alata germplasm. In the present study, 45 accessions conserved in the National repository of tuber crops germplasm at ICAR-CTCRI, Sreekariyam were characterized based on 25 qualitative and 13 quantitative traits including the major yield components and three biochemical characteristics. There were no duplicate accessions identified based on the morphological classification and it can be maintained as core collection. The biochemical study on dry matter, starch, sugar and crude protein content were carried out to determine the nutritional quality of the accessions studied. The dry matter percentage ranged from 27.53 to 48.24 percent. The percentage starch content of the accessions ranged from 36.0 to 65.2 and 13.2 to 26.4 on dry and fresh weight basis respectively.Sugar content ranged from 2.4 to 9.6 percent on dry weight basis. Crude protein content on dry weight basis varied from 5.86 to 14.51 percent and Da331 recorded the maximum crude protein content. The genetic diversity on molecular basis was determined using nine SSR and 15 ISSR markers. All the SSR primers and ISSR primers studied showed very high polymorphism. The ISSR primerson an average produced 9 polymorphic alleles with mean observed heterozygosity (Hobs) and values of polymorphism information content (PIC) 0.8619 and 0.8472 respectively. The SSR primers on an average produced six polymorphic alleles. TheHobs and PIC values obtained were 0.6904 and 0.6614 respectively. Highest number of bands was obtained for the SSR primer Dab2C05 and lowest in SSR YM 5. Clustering based on ISSR marker analysis grouped the genotypes in to four clusters. Da 99 and Da 81 recorded high similarity (0.98). The Clusters 1, 2 and 4 have only one accession each i.e. Da 331, Da 243 and Da 340 respectively. Clustering and Principal Component Analysis (PCA) of the data validated the variation among the Dioscorea alata accessions. The distribution of accessions in the scatter plot revealed high divergence of Da340, Da331 and Da 390.Based on SSR marker analysis, the genotypes formed 3 clusters at 0.37 dissimilarity index. and Da 120 and Da 56 showed higher similarity (0.97).Cluster 1 have only one accession (Da 52) forming an outlier and cluster 3 have two genotypes Da 331 and Da 340. The highly polymorphic ISSR and SSR primers identified can be used for further genetic diversity characterization in future. The results from the present study serves to facilitate the development of better varieties by plant breeding and marker assisted breeding programs.