Multivariate analyses of phenotypic traits in some specious of Pear (Pyrus spp. )

The most basic step in fruit tree breeding programs is the collection and evaluation of internal and external germplasm. The aim of this study was to evaluate the genetic diversity and grouping of the studied pear species based on 48 important quality traits of leaves, shoots, blossoms and fruits and to determine the genetic distance between them with identify cultivars suitable for cultivation and use them in breeding programs. Iran with more than ten species of pear and genetic diversity proximity centers to the product as an important source of genetic product is well-known in the world. Despite this privileged geographical location for pears in the country, so far, there is no accurate information about the genetic relationship between different pear genotypes in Iran, for the proper use of native genotypes for pear breeding purposes.

This study was conducted in 2018, with the evaluation of 13 pear species from eastern and western species in Karaj research institute for seed and seedling improvement and preparation of Lorestan university of horticultural sciences. In this study, three general traits of the tree, five traits of branches, 13 traits of leaves and petioles, six traits of blossoms and 20 traits of fruit were evaluated according to the national descriptor of differentiation, uniformity and stability (DUS) tests, which is a localized version of the international union for conservation of pear (UPOV) examination, uniformity and stability test instructions. In this study, cluster analysis was performed by Ward method.

The results of the evaluation of the studied traits showed that there was a high diversity in the characteristics of fruit size, the position of the largest fruit diameter, fruit shape, tip shape and leaf base among the studied species. In this study, cluster analysis was performed by Ward method using all the studied traits. The studied species were divided into three main groups at a distance of 400, so that Asian, native and European species were included in a separate group. The results of simple correlation of traits showed that leaf related traits such as length and width of the leaf had a positive correlation with the amount of fruit traits. Also, the highest negative and significant correlation was observed between the position traits of the largest fruit diameter and petal shape. The results of principal component analysis (PCA) showed, that the 11 main factors justify 97.99% of the total variance. Among the components, the first and second factors, which were mostly related to trunk strength, fruit and leaf traits, justified nearly 50% of the variance.

Based on the results, among the studied traits of fruit shape and size, leaf traits were the most important traits for detecting the diversity of pear species. This study showed that eastern and western pear species have significant diversity and are a valuable resource for plant breeding research.