Characterization of selected accessions of cassava germplasm using morphological and molecular markers

Abstract

Cassava (Manihot esculenta Crantz), a perennial shrub, is an important crop in many parts of the tropics.This research work attempts morphological and molecular characterization of 27 cassava germplasm collected from Southern India. In the present study27 accessions of cassava maintained in the field genebank of ICAR- Central Tuber Crops Research Institute, Sreekariyam, Thiruvananthapuram were characterized based on 20 qualitative and 10 quantitative traits including the major yield components. There were no duplicate accessions identified based on morphological classification and it can be maintained as core collection. The genetic diversity on molecular basis was evaluated using 10 SSR primers. Molecular markers are proved to be valuable tools in the characterization and evaluation of genetic diversity within and between species and population. All the SSR primers in the study showed the polymorphism. The SSR primers on an average produced 9 polymorphic alleles with mean observed hetrozygosity and values of Polymorphism Information Content (PIC) 0.8293 and 0.8091 respectively. The value of heterozygosity here ranged from 0.2975 (SSRY 148) to 0.8293 (SSRY 9). The PIC value ranged from 0.2533 (SSRY 148) to 0.8091 (SSRY 9). The hetrozigosity and average PIC content observed in SSRY 9. Clustering based on morphological descriptors and molecular markers was done. In morphological clustering, Cluster-I consists of 7 accessions was further subdivided into two sub clusters I A and I B. Cluster-I A consisted of four accessions while Cluster-I Bof three accessions. The bigger cluster Cluster-II consisting of 20 accessions was found to have two subgroups namely II A with 12 accessions and II B with 8 accessions. Clustering based on SSR marker analysis grouped the genotypes into 2 Clusters. Cluster-I contain 6 accessions was further sub grouped into I A and I B with 3 accessions each. Cluster II with 21 accessions was found to have two subgroups II A with 13accessions and II B with 8 accessions. By comparing the morphological and molecular clusters, In Cluster II of each dendrogram have 6 similar accessions of cassava (TCR-5, TCR-10,TCR-15,TCR- 45,TCR-79,TCR-69,). Clustering and Principal Componant Analysis of the data validated the variation among the cassava accessions. In PCA of morphological characters the percentage variation obtained in PC component 1 (54.22). Mantel’s test proves that there is no correlation between the morphological and molecular data. The present results indicated that the primers selected for the present study will be useful for future genetic variability studies and would provide breeders with a genetic base for selection of diverse parents for crop improvement programmes in cassava.