-This study assessed variability, heritability and correlations of agronomic traits in an onion

Genetic diversity and structure of plant germplasm collections, frequently determined by molecular markers, can be used to assist breeding programs, to validate core collections determined by other methodologies, to identify priority accessions for conservation, and to confirm genetic integrity after regeneration. This research aimed to study the genetic diversity and structure of the Uruguayan white dent maize collection, to evaluate the genetic representativeness of its core collection (previously defined by phenotypic traits), and to confirm the genetic integrity of seven regenerations made in Mexico and Uruguay in comparison with the original accessions. Ninety accessions were fingerprinted using 26 simple sequence repeat (SSR) markers. Genetic structure was analyzed by Ward clustering, canonical analysis, and a Bayesian approach based on allelic frequencies. All SSR markers were polymorphic with a mean number of alleles (A) of 7.43, an effective allele number (Ae) of 3.04, and expected heterozygosity of 0.579. The genetic variation between accessions was 0.251, and variation within accessions was 0.749. Four genetic groups were obtained using the three approaches. The core collection represented the structure of the whole collection because the four genetic groups were proportionally represented. The genetic diversity in the core collection did not differ from the entire collection in A, Ae, expected heterozygosity (He) percentage of polymorphic loci (%P), and expected heterozygosity within accessions (Hs). Most regenerations (9 out of 14) preserved the genetic integrity of original accessions, whereas in other cases, either new or lost alleles caused genetic differences. The analysis of genetic structure and diversity of germplasm collections, in combination with morphological characterizations, helps to define ex situ conservation strategies and usage in breeding programs.

Bulk sampling and subsequent DNA fingerprinting are applied to obtain estimated allelic frequency data and unveil population structure for outbreeding species. We developed 'Gametes Simulator', a routine to simulate gametes from allelic frequencies of unlinked loci, which enables the analysis of population structure through Bayesian analysis. Based on the allelic frequencies in the populations, the software simulates the alleles per population in the right proportions and assigns one allele per marker to each gamete following Mendel's laws that govern gametogenesis.