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Building the basis for population breeding: Genetic structure and diversity of maize populations in Portugal

Maize was introduced in Portugal in the XVI century and many traditional landraces have been developed since then, adapted to specific regional growing conditions, as well as farmers needs. Nowadays, the enduring landraces are mainly flint type open pollinated varieties (OPV) with technological ability for production of the traditional maize leavened bread called “broa” (Brites et al., 2010). Only a few preliminary studies have been developed on the characterization of the breeding potential of this germplasm (Vaz Patto et al., 2007, 2009). Under the SOLIBAM European project - Strategies for Organic and Low-input Integrated Breeding and Management, we thoroughly analysed the phenotypic and molecular diversity of 35 maize Portuguese populations (enduring traditional landraces and participatory breed OPVs). Our objectives were: (1) Analyse the phenotypic and molecular diversity within and among the maize populations, (2) Test for deviations from Hardy-Weinberg equilibrium, at individual loci, (3) Test for linkage disequilibrium, between pairs of loci. Thirty individuals per population were fingerprinted with 20 microsatellite markers uniformly distributed throughout the genome. The phenotypic HUNTERS evaluation and yield were measured on a plot basis on the multi-location trials (6-9 locations). The studied populations will be classified into distinct clusters using three different multivariate approaches (principal component, cluster and discriminating analysis). Analysis of molecular variance will be used to test the existence of significant differences, at the genetic level, between the identified phenotypic clusters. This study will allow us to characterize the genetic structure of these populations, establishing the basis for an efficient use of this germplasm in breeding programs, and to evaluate the suitability of these populations for association mapping studies.

population breeding; open pollinated varieties; multi-location trials; SSRs; genetic structure

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