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Nowadays European consumers are more concern about the quality of their food and about agrodiversity erosion and unsustainability of agricultural ecosystems. Centuries of maize cultivation in Portugal have originated a very diverse germplasm with particular quality for food production (sourdough 'broa' bread) and with great value for breeding. Traditional Portuguese maize bread, with particular nutritional value, has high potential to become a popular speciality fighting health and sustainability public concerns. A diverse collection of inbred lines derived from traditional Portuguese germplasm has been developed and conserved at the Portuguese Plant Germplasm Bank (BPGV). In order to determine the potential of this collection for an association mapping approach aimed to identify the genetic basic of bread making quality, we studied its genetic diversity and population structure. 150 maize BPGV inbred lines were screened using 50 SSR makers uniformly distributed throughout the genome. A number of genetic diversity parameters was calculated (Na, NO, HE, PIC) for all loci as well as the proportion-of-shared-alleles distance between pairs of lines. All showed the existence of large variability among inbreeds. The Neighbor Joining tree depicted well the pedigree records of inbreds. Presently, linkage disequilibrium and the genetic structure of the collection are being analyzed. This information together with the phenotypic characterization of the lines will be crucial to select the most appropriate group of inbreds for the future association studies reducing the risk of false positives and maximizing the detection of significant marker-trait association.

Through several centuries of natural and human selection, a very diverse maize germplasm has been developed in Portugal. Portuguese maize landraces have been preserved on farm, due to particular quality traits not found on their competing modern hybrid varieties. These landraces are mainly flint type open pollinated varieties (OPV) with technological ability for the production of the traditional maize leavened bread called “broa”. To clarify if the quality of these landraces is related with their genetic diversity, 46 OPVs collected from a known high quality maize bread Portuguese region, plus six participatory maize improved Portuguese landraces and two American populations as controls, were analyzed for eight different parameters related with their technological ability for bread production, and 13 SSR markers. Using three different multivariate analyses including principal component, cluster and discriminant analysis it was possible to classify these OPVs into three distinct clusters based on the quality traits. However, the farmer’s selection has not resulted in changes in the genetic diversity population structure. Quality group A and group B are not significantly different at genetic level. Still, the studied populations are characterized by a broad genetic diversity. Based on the existence of diversity at molecular level and high quality, the Portuguese maize landraces conserved on farm represent valuable germplasm with high potential for bread quality improvement. On farm breeding projects taking into consideration quality aspects should be promoted as a way to preserve and improve these unique maize landraces in risk of disappearing.

Maize arrived in Portugal from America during the XVI century and spread rapidly throughout the country. Numerous open pollinated traditional varieties (landraces) have been developed during the centuries of cultivation, adapted to specific regional growing conditions as well as farmer’ s needs, and represent a valuable genetic resource for breeding and genetic studies. Concern has been expressed that genetic diversity might be reduced by natural and artificial (human) selection. However, traditional Portuguese farmers were trained to preserve variability as a way to guarantee production under any circumstance. In 1984, P&ecirc ; go started, with CIMMYT support, an on-farm participatory maize breeding project at the Portuguese Sousa Valley region (VASO). It concerned mainly flint-type open pollinated landraces with technological ability for production of the traditional maize bread called “ broa” . “ Broa” production still plays an important economic and social role in Central and Northern Portuguese rural communities. This bread making ability depends on a range of particular traits not found on the available commercial hybrid varieties and this is probably why traditional maize landraces have not, in these regions, been totally replaced by hybrid varieties. In the VASO project, a particular landrace ‘ Pigarro’ was selected from the traditional populations cultivated in this region. Participatory plant breeding using mass selection was carried out each year and seed was stored from each selection cycle. Production and ear size increased and root lodging decreased along this selection process. Our present objective is to evaluate the impact of participatory plant breeding upon ‘ Pigarro’ genetic diversity over an interval of 20 years of selection. For this purpose, 30 randomly selected individuals from each of three different selection cycles (1984, 1993 and 2004) were fingerprinted with 10 SSR markers uniformly distributed across the maize genome. Allelic richness and gene diversity will be assessed for each selection cycle and genic and genotypic differentiation among cycles will be tested and discussed.

Portugal, with its privileged historical and geographical position as an enter point of new species in Europe, soon has contacted with and cultivated maize. A very extended collection of maize germplasm has been preserved in the Portuguese Bank of Plant Germplasm (BPGV) in Braga, Portugal. The traditional Portuguese maize landraces here maintained, may represent valuable source of interesting genes to introduce into modern cultivars. In the present study, microsatellite markers were used for germplasm analysis and estimation of the genetic relationship between 104 accessions of Zea mays L. from the Portuguese gene bank collection. 102 maize accessions were chosen to represent the diversity of dent and flint maize germplasm found in Portugal in the past. The American elite inbreds, B73 and Mo17, were included in the analysis for comparison. Seven SSRs loci, located on different chromosomes and with different repeat types and repeat base compositions, were selected from MaizeDB (www.agron.missouri.edu) for the analysis. The number of alleles per microsatellite marker varied from 2 to 25, with an average of 8.29, and a total of 58 different alleles were detected. The polymorphism information content (PIC), a measure of the allelic diversity at a locus, was estimated as described on Botstein et al. (1980) for each of the polymorphic SSR loci detected in the present study. The detected PIC values varied from 0.375 to 0.9011, with an average of 0.7010. The proportion of shared alleles distance (Dps) (Bowcock et al., 1994), defined as 1 - the proportion of shared alleles between the multiple locus genotype of two individuals, was calculated. Among the 102 Portuguese maize accessions, the average distance was 0.7622, with a minimum of 0 (indistinguishable pairs) for 3 pairs of lines and a maximum of 1 (with no common alleles) for 696 pairs of lines showing the existence of large variability between accessions. The average distance of Mo17 to the 102 other accessions was 0.8065, and of B73 was 0.7497. In order to visualize the relationship among the maize accessions, cluster analysis was performed with NTSYS-pc based on the unweighted pair-group method with arithmetic average (UPGMA). The cophenetic correlation coefficient was calculated, and Mantel's test was performed to check the goodness of fit of a cluster analysis for the matrix on which it was based. The same procedure was employed to calculate cophenetic correlation coefficients among matrices based on different distance measures. Cluster analysis showed a good fit to the matrix on which it was based giving significant cophenetic correlation coefficient (r = 0.5684 ; p < 0.001 ; 1000 permutations). The resulting dendrogram point up that almost all of the accessions could be distinguished and clustered into two large groups. Within these two broad germplasm groups, accessions were grouped in a manner that is to some extent consistent with their known pedigree. The indistinguishable pairs of accessions were accessions with a common origin. The pattern of genetic variation among these maize accessions was investigated by the analysis of molecular variance (AMOVA) approach (Excoffier et al., 1992) using WINAMOVA 1.55 program. Total genetic variation was partitioned according to a number of traits important both in breeding and for line identification (as endosperm type, kernel and cob colour, plant height and initial plant vigour). Different groups of accessions were established in agreement to these different grouping patterns. The significance of  -statistics was obtained non-parametrically by 1000 permutations. Although most of the genetic diversity was attributable to differences among accessions within the different groups established (around 96% in all the cases), significant  -values among groups (p

Portugal, by its priviledge historical and geographical position as enter point of new species in Europe, was among the first European nations to adopt maize (Zea mays L.) in its agricultural systems, more than five centuries ago. The traditional Portuguese maize landraces maintaned at the Portuguese Plant Germplasm Bank (BPGV), represent a source of valuable genes for introduction into modern cultivars. Knowledge of germplasm diversity is crucial for planning crosses in line development, plant variety protection and conservation management. The purposes of this work were to assess, with microsatellite (SSR) DNA molecular markers, the genetic diversity among maize Portuguese breeders inbred lines and compare this with world wide representatives.