Assessment of variability within and among four Pyrus species using multivariate analysis

Abstract

The morphological diversity and relationship of 48 accessions belonging to four Pyrus species including 25 P. communis, 11 P. glabra, 8 P. syriaca and 4 P. pyrifolia accessions were evaluated from different regions of Iran by using 32 morphometric traits of the trees and the fruits. Significant diversity was observed not only among the samples of different species, but also among the accessions in the same species. Several fruit characteristics including weight and dimensions of fruit, curvature of stalk, width of eye basin as well as tree attributes including thorns of shoots, width of leaf blade, and curvature of longitudinal axis were among the traits with high level of variation among the accessions. P. pyrifolia and P. glabra had the highest and the lowest fruit weight, dimensions and juiciness, respectively. There was significant positive correlation between fruit weight and leaf dimension and negative correlation between fruit weight with fruit firmness and TSS/TA. The shape of base, length and width of leaf blade were also negatively correlated with fruit firmness. According to principal components analysis (PCA), seven components accounted for 82.95% variance. Fruit size and texture as well as leaf size were prevalent in the first component with 41.82% of total variance and had the highest power of discrimination; they were the most useful traits for genetic characterization of Iranian pear germplasm. Bi-plot and cluster analysis divided the accessions into three main groups according to the species source with accessions from the same geographical areas, being more closely related and clustered in the same sub-groups. Our results provide useful information about morphological relationships of Pyrus spp. in Iran and indicate that there are high phenotypic (and presumably genetic) diversity in Iranian pears that merit conservation action and utilization in the breeding programs.