Simple sequence repeat (SSR) markers are effective for identifying pear cultivars and selections

Abstract

The present study characterized and identified pear cultivars growing in the southern region of Minas Gerais State, Brazil, using microsatellite markers. Nineteen (19) pear cultivars were collected from two sites of Southern Minas Gerais State: Ribeirão Vermelho and Lavras. DNA was extracted from newly formed leaves and amplified using 21 simple sequence repeat (SSR) markers (NH001c, NH002b, NH005b, NH007b, NH008b, NH009b, NH011b, NH013b, NH012a, NH014a, NH015a, NH017a, KA4b, KA5, KA14, KA16, KB16, KU10, BGA35, BGT23b and HGA8b). The data was analyzed by examining unweighted pair group method with arithmetic mean (UPGMA) clustering, principal coordinate analysis, the Shannon index, and the expected heterozygosity for each primer. The markers used were efficient in separating the Asian and European cultivars as well as hybrids. The primer KA16 was noteworthy in distinguishing the species Pyrus communis, Pyrus pyrifolia and Pyrus betulaefolia by its different banding patterns. Grouping by principal coordinates was similar to UPGMA clustering, forming two distinct groups among the Asian and European pears. The Shannon index and the expected heterozygosity had medium values of 0.440 and 0.300, respectively. The pear cultivars from Southern Minas Gerais usually show low productivity, mainly due to the lack of improved strains for less-demanding weather (warmer) conditions. The selection of the most suitable materials would contribute considerably to overcoming this problem, and the markers selected here can be used in separating cultivars - and presumably contribute to the selection of better matrices.

Key words: Pyrus sp., Rosaceae, microsatellite, heterozygosity.