Genetic diversity of maize landraces from the South-West of France

Abstract

From the 17th century until the arrival of hybrids in 1960s, maize landraces were cultivated in the South-West of France, a traditional region for maize cultivation. A set of landraces were collected in this region between the 1950s and 1980s and were then conserved ex situ in a germplam collection. Previous studies using molecular markers on approx. twenty landraces fo this region showed that they belonged to a Pyrenees-Galicia Flint genetic group and originated from hybridization between Caribbean and Northern Flint germplasms introduced in Europe. In this study, we assessed the structure and genetic diversity of 194 SWF maize landraces to elucidate their origin, using a 50K SNP array and a bulk DNA approach. We identified two weakly differentiated genetic groups, one in the Western part and the other in the Eastern part. We highlighted the existence of a longitudinal gradient along the SWF area that was probably maintained through the interplay between genetic drifts and restricted gene flows, rather than through differential climatic adaptation. The contact zone between the two groups observed near the Garonne valley may be the result of these evolutionnary forces. We found only few significant cases of hybridization between Caribbean and Northern Flint germplasms in the region. We also found gene flows from various maize genetic groups to SWF landraces. Thus, we assumed that SWF landraces had a multiple origin with a slightly higher influence of Tropical germplasm in the West and preponderance of Northern Flint germplasm in the East.

Genome-wide SNP genotyping of DNA pools identifies untapped landraces and genomic regions that could enrich the maize breeding pool

“…landraces from northern Spain and southwestern France, located along the Pyrenean Mountains, were admixed either with Caribbean or Northern Flint. This result supports the hypothesis that new Pyrenean-Galicia Flint groups originated from hybridization between Caribbean and Northern Flint material that were introduced in southern Spain and northern Europe, respectively (27,29,59)…”

Genotyping of DNA pools identifies untapped landraces and genomic regions to develop next‐generation varieties

“…Some landraces from northern Spain and southwestern France, located along the Pyrenean Mountains, were admixed either with Caribbean or Northern Flint. This result supports the hypothesis that new Pyrenean‐Galicia Flint groups originated from hybridization between Caribbean and Northern Flint material that were introduced in southern Spain and northern Europe, respectively (Brandenburg et al ., 2017; Camus‐Kulandaivelu et al ., 2006; Diaw et al ., 2020). Interestingly, some southwestern Spanish landraces have elevated admixture with Italian Flint groups and are closely related to Italian landraces on the NJ tree (Figure S5), while northern Spanish landraces (latitude >42°N) do not.…”

Deciphering the Genetic Diversity of Landraces With High-Throughput SNP Genotyping of DNA Bulks: Methodology and Application to the Maize 50k Array

“…As proof of concept, we used the DNA pooling approach to estimate allelic frequencies in maize landraces in order to identify original maize landraces in germplasm for pre-breeding purposes and selective footprints between geographic and/or admixture groups of landraces cultivated in contrasted agro-climatic conditions ( Arca et al, 2020 ). Our approach could be very interesting for studying plant germplasm since time, money and molecular skills can be limiting factors to study and compare large collections of landraces maintained in seedbank ( Mir et al, 2013 ; Diaw et al, 2020 ). Applications could be expanded to QTL identification in pools ( Gallais et al, 2007 ), detecting signatures of selection in multi-generation experiments, or detection of illegitimate seed-lots during multiplication in genebanks.…”