Records of the occurrence of wild relatives of maize in South American lowlands are unprecedented, especially in sympatric coexistence with landraces. This fact is relevant, because regions of occurrence of wild relatives of cultivated plants should be a priority for conservation, even if they do not correspond to the center of origin of the species. The aim of this study was to identify and characterize the wild relatives of maize in the Far West of Santa Catarina, southern Brazil. Therefore, phenotypic characterization was performed for five populations, based on 22 morphological traits deemed as fundamental for classifying the species of the genus Zea, and validated through the characterization of chromosomal knobs of two populations. The occurrence and distribution of teosinte populations were described through semi-structured interviews applied to a sample of 305 farmers. A total of 136 teosinte populations were identified; 75% of them occur spontaneously, 17% are cultivated populations, and 8% occur both ways, for the same farm. Populations that were characterized morphologically had trapezoidal fruits mostly, upright tassel branch (4–18), non-prominent main branch and glabrous glumes, with two protruding outer ribs and 8 inner ribs, on average. Cytogenetic analysis identified 10 pairs of homologous chromosomes (2n = 20) with 26 knobs, located in the terminal region of all chromosomes. The similarity of these results with the information reported in the literature indicates that the five populations of wild relatives of maize in this region of Santa Catarina belong to the botanical species Zea luxurians.

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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.

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A germplasm collection should represent the diversity of the target species and the gene pools associated with it. However, it is critical to establish collection plans which ensure such representativeness. At times it is difficult to identify the best strategy for collecting domesticated species that are conserved in situ/on farm, since, in general, the magnitude of the diversity existing in a geographical area was hitherto unknown. The Diversity Census methodology was developed for previous diagnosis of the diversity of Zea mays subsp. mays L., conserved by farmers in two municipalities in the far western region of the state of Santa Catarina, southern Brazil. The Diversity Census database allowed for the identification of the best strategy to collect different types of maize landraces. Thus, tests were carried out using two methods described for Core Collections (Modified Random Sampling and Maximization) and a third statistical method for random sampling, stratified by farm area. The Maximization method enabled the capture of all the morphological variation of the traits evaluated in the Diversity Census from the smallest sample size. The relevance of this result is the feasibility of adapting the Core Collection strategy in order to plan more efficient expeditions to collect maize landraces conserved in microregions. Such planning allows for organizing the collection work efficiently, reducing costs, simplifying the work of characterization and helping to plan integrated strategies of in situ/on fam conservation.

Resumen La co-evolución de plantas, ambientes y culturas hace posible la existencia de variedades vegetales denominadas criollas. Conservadas de forma dinámica por agricultores, constituyen elementos identitarios de las comunidades productivas en las que son mantenidas para satisfacer necesidades alimenticias, medicinales, culturales, entre otras. Esta investigación aporta evidencias empíricas para la comprensión de los procesos culturales y conocimientos tradicionales asociados al cultivo de variedades criollas, desarrollados y compartidos por agricultores familiares en tres localidades uruguayas, en un contexto de homogeneización de la agrodiversidad. A partir del análisis de entrevistas e instancias de observación, los resultados indican que existen motivos productivos, a la vez que afectivos y emocionales para la conservación in situ de decenas de variedades criollas integradas a los sistemas productivos y mundos de vida de dos tipos de agricultores: tradicionales y neorrurales. Ambos tipos de productores desarrollan conocimientos, prácticas y significados vinculados a las variedades criollas que atesoran como recursos propios en procesos de interdependencia entre naturaleza y comunidad.