Background and Aims The number of plastome sequences has increased exponentially during the last decade. However, there is still little knowledge of the levels and distribution of intraspecific variation. The aims of this study were to estimate plastome diversity within Zea mays and analyze the distribution of haplotypes in connection with the landrace groups previously delimited for South American maize based on nuclear markers. Methods We obtained the complete plastomes of 30 South American maize landraces and three teosintes by means of Next Generation Sequencing and used them in combination with data from public repositories. After quality filtering, the curated data was employed to search for SNPs, INDELs and cpSSRs. Exact permutational contingency tests were performed to assess associations between plastome and nuclear variation. Network and Bayesian phylogenetic analyses were used to infer evolutionary relationships among haplotypes. Key Results Our analyses identified a total of 124 polymorphic plastome loci, with the intergenic regions psbE-rps18, petN-rpoB, trnL_UAG-ndhF and rpoC2-atpI exhibiting the highest marker densities. Although restricted in number, these markers allowed the discrimination of 27 haplotypes in a total of 51 Zea mays individuals. Andean and lowland South America landraces differed significantly in haplotype distribution. However, overall differentiation patterns were not informative with respect to subspecies diversification, as evidenced by the scattered distribution of maize and teosinte plastomes in both the network and Bayesian phylogenetic reconstructions. Conclusions Knowledge of intraspecific plastome variation provides the framework for a more comprehensive understanding of evolutionary processes at low taxonomic levels and may become increasingly important for future plant barcoding efforts. Whole-plastome sequencing provided useful variability to contribute to maize phylogeographic studies. The structuring of haplotype diversity in the maize landraces examined here clearly reflects the distinction between the Andean and South American lowland gene pools previously inferred based on nuclear markers.

Maize (Zea mays ssp. mays) is a major cereal crop worldwide and is traditionally or commercially cultivated almost all over the Americas. The North-Western Argentina (NWA) region constitutes one of the main diversity hotspots of the Southern Andes, with contrasting landscapes and a large number of landraces. Despite the extensive collections performed by the “Banco Activo de Germoplasma INTA Pergamino, Argentina” (BAP), most of them have not been characterized yet. Here we report the morphological and molecular evaluation of 30 accessions collected from NWA, along an altitudinal gradient between 1120 and 2950 meters above sea level (masl). Assessment of morphological variation in a common garden allowed the discrimination of two groups, which differed mainly in endosperm type and overall plant size. Although the groups retrieved by the molecular analyses were not consistent with morphological clusters, they showed a clear pattern of altitudinal structuring. Affinities among accessions were not in accordance with racial assignments. Overall, our results revealed that there are two maize gene pools co-existing in NWA, probably resulting from various waves of maize introduction in pre-Columbian times as well as from the adoption of modern varieties by local farmers. In conclusion, the NWA maize landraces preserved at the BAP possess high morphological and molecular variability. Our results highlight their potential as a source of diversity for increasing the genetic basis of breeding programs and provide useful information to guide future sampling and conservation efforts.

Las variedades locales de maíz presentan una gran relevancia socioeconómica en los sistemas agrícolas familiares de la provincia de Misiones. La pérdida de costumbres y tradiciones asociadas a su uso ponen en riesgo su conservación. Con el fin de aportar al conocimiento de la variabilidad genética local, contribuir a la conservación, revalorización y utilización de estos recursos, se estudiaron 16 poblaciones nativas de diferente origen y fecha de colecta mediante descriptores agromorfológicos. Los resultados permiten concluir que 1) las poblaciones nativas evaluadas albergan niveles considerables de variabilidad genética; 2) Se mantiene la identidad de razas dentro de cada origen; y 3) existe una tendencia al aumento de productividad en las colectas actuales. Esto pone de manifiesto, por un lado, la existencia de barreras geográficas y culturales que preservan el ideotipo, y por otro, la naturaleza dinámica de la conservación sometida a procesos de selección, sustitución y/o introgresión genética.

Los Recursos Fitogenéticos se conservan ex situ en bancos de germoplasma. Para que los mismos sean utilizados por los mejoradores deben ser caracterizados y evaluados. En el banco de Germoplasma del INTA Pergamino se realiza la caracterización y evaluación de poblaciones locales de maíz, donde los datos obtenidos pueden presentarse como matrices de tres vías (poblaciones * variable * ambiente). A partir de datos empíricos de tres vías se generaron datos simulados, los cuales se utilizaron para comparar las técnicas de Análisis de Componentes Principales (ACP), Análisis Factorial Múltiple (AFM) y Análisis de Procrustes Generalizado (APG). La correlación entre las matrices de datos se cuantifi có con el coefi ciente RV de Escoufi er. Los resultados muestran una alta concordancia entre las confi guraciones encontradas con las tres estrategias de análisis. Se destaca el potencial que tienen AFM y el APG en el estudio de la interacción genotipo-ambiente multivariada. También se pudo comprobar que el coefi ciente RV de Escoufi er, puede ser usado como una sencilla herramienta para cuantifi car dicha interacción.