Karyotypic study of wild pear species of Fars Province, Iran

Abstract

Introduction. Iran, with more than 10 species of Pyrus, is one of the important genetic resources for this genus in the world, and Fars province is one of the centers of origin. In our research, cytogenetical investigation of native wild pear species of Fars province, including P. glabra Boiss., P. syriaca Boiss. and, probably, a natural hybrid of them, (P. glabra × P  syriaca), was carried out using a video analysis system. Materials and methods. Seed germination of different species was done on damp filter paper in petri dishes, and root tips were collected for karyotypical investigation. After pretreatment, fixation, hydrolysis and staining, samples were prepared for observation under the microscope and chromosome morphology was studied. Analysis of the species genome (length of each chromosome, length of long and short arm, ratio of long arm to short arm and ratio of short arm to long arm) was done and the chromosomal type of each species was determined using Levan et al.'s method. Then the karyotypic symmetry of species was studied by Stebbins' method. Results and discussion. The results revealed that all of the genotypes, with 2n = 2x = 34, were diploid. Based on Stebbins' table, genotypes 1 and 2 of P. glabra were classified into group 1A, P. glabra × P. syriaca into group 2A and P. syriaca into group 2B. Genotype plots, according to the A1 and A2 parameters and Stebbins' cross classes, revealed the same results. Similarity and differences of species in chromosomal aspects were investigated and the results shown in a dendrogram.