Genetic similarity among onion cultivars of different types and origins, based on AFLP markers

Abstract

The genetic similarity among onion cultivars of different origins was evaluated, in order to carry out genetic resources and breeding programs for this species on the Brazilian Northeast. Forty-one onion cultivars were analyzed for 146 polymorphic Pst1/Mse1 AFLP bands, according to UPGMA phenogram, built with the Jaccard's similarity coefficient matrix. The phenogram co-phenetic value was estimated in 0.91 showing a good adequacy of the data. In the phenogram were observed two main onion groups at the cut point of 0.55 of similarity: 1) group composed of predominantly Brazilian cultivars, with some inclusion of foreigners; and 2) group with three foreign cultivars (Mercedes, Perfect and TEG 502 PRR). Rijnsburger Jumbo and IPA 8 presented the largest similarity (85%), while Madrugada presented the greatest dissimilarity to the other cultivars. The cultivars developed by IPA were split in sub-groups within the group 1: IPA 8, IPA 10 and IPA 11; IPA 12, IPA 7, IPA 2 and IPA 6; IPA 3, IPA 4 and IPA 9, suggesting that genetic variability could be explored by crosses among cultivars from different IPA subgroups. Bola Precoce and BRS Cascata presented the greatest similarity among the Brazilian cultivars. A similarity greater than 39% was observed, suggesting a high genetic variability of the analyzed onion collection. Introduction of new cultivars should take in consideration other origins than USA, in order to increase the genetic variability of onion germplasm in the Northeast Brazil.