Cluster analysis carried out on the matrix of Euclidean distances. To assess the weight of each morphological character, principal component analysis (PCA) was used. According to the results obtained, eigenvalue was maximum in PC-I (13.88) followed by PC-II (11.42) and PC-III (7.32). The first fifteen PCs with Eigenvalues >1 contributed 74.08% of the variability. The results suggested that these molecular markers were convenient and polymorphic enough to distinguish all of the studied accessions. The present study provides significant information in genetic variability of Turkish pea genotypes. Keywords: Cluster, diversity, pea, polymorphism
The legumes are the third most abundant family of the flowering plants including more than 650 genera and 18,000 species (Lewis et al., 2005). Among these, pea (Pisum sativum L.) is the sixth major pulse crop cultivated throughout the world and is ranked as the second highest yielding legume globally after the common bean (Kumari et al., 2013).
The center of pea genetic diversity is the broad area of the “Fertile Crescent” through Turkey, Syria, Iraq, Israel, and Lebanon (Symkal et al., 2013). Different studies about genetic diversity of Pisum taxa have used morphological characters and agronomical traits (Yirga et al., 2013, Gixhari et al., 2014; Ouafi et al., 2016). A number of methods are available for analysis of morphological diversity in a germplasm. As a multivariate statistical technique, the principal components analysis (PCA) has the ability to transform a number of possibly correlated variables into a smaller number of variables called principal components (Ziegel, 2002).
Morphological markers are largely affected by environmental factors compared to biochemical and molecular markers. Therefore, molecular markers are the means to overcome the limitations associated with these markers (Rao, 2004) as the estimation of genetic diversity through molecular markers is independent of environmental influences (Tatikonda et al., 2009). Simple sequence repeats (SSRs) have increasingly become the marker set of choice for genetic studies, as they are abundant, highly polymorphic, codominant in nature, and genome-speciﬁc (Cuevas and Prom, 2013; Izzah et al., 2013). Being so important, SSR markers were previously used for assessing genetic diversity in pea (Taran et al., 2005; Nasiri et al., 2009; Nisar et al., 2017).
Despite their great economic importance, the majority of Turkish pea landraces have not been characterized. The objective of this study was to determine the population-level genetic diversity of these accessions based on morphological and molecular markers as a contribution for future breeding and genebank management programs.
The present study was designed to investigate the genetic diversity among Turkish pea accessions through the analysis of morphological characters and microsatellites (SSRs). The application of modern molecular markers in pea includes marker-assisted selection, identification of regions affecting quantitative trait loci (Tar’an et al., 2005), and estimation of diversity (Baranger et al., 2004). Comprehensive analysis of genetic diversity could be useful for genetic and genomic analysis and the utilization of genetic variation in pea breeding (Nisar et al., 2017). Morphological traits used in this study demonstrated significant differences among accessions. Clustering of accessions by multivariate analysis may provide advantages to plant breeders.
Pea is an important crop for Turkey because of its contribution to the development of the agricultural industry. Results indicate that the Turkish pea collection maintains a significantly high variability. This richness of Turkish pea genetic resource can be used in cultivar improvement programs and breeding studies. Members representing certain traits or groups of traits may be recommended for specific breeding programs.