Biology subjects

Debille, S.

Publications and source records attributed to Debille, S..

2 recordsLinked to original sources

bioRxiv2022

Pollen contamination and mating structure in maritime pine (Pinus pinaster Ait.) clonal seed orchards revealed by SNP markers

Maritime pine (Pinus pinaster Ait.) is a major forest tree species in south-western Europe. In France, an advanced breeding program for this conifer species has been underway since the early 1960s. Open-pollinated seed orchards currently supply more than 90% of maritime pine seedlings for plantation forestry. However, pollen contamination and mating structure have been poorly studied in such seed orchards whereas they could impact genetic gains and diversity. We analyzed these features in three maritime pine clonal seed orchards. We addressed biological (tree genotype, age, flowering phenology) and environmental factors (vicinity with external pollen sources, orchard structure, soil type, climatic conditions) that are expected to determine the genetic composition of seed lots. Genetic analyses were based on an optimized set of 60 SNP markers and performed on 2,552 seedlings with Cervus software (likelihood inference methodology). Pollen contamination rates were highly variable between seed lots (from 20 to 96%), with a mean value of 50%. Interpretative factors included the distance between the seed orchard and external pollen sources, rain during the pollination period, seed orchard age, soil conditions and seed parent identity. All parental genotypes from the seed orchards contributed to the offspring as pollen parents, but differences in paternal reproductive success were detected. Finally, the overall self-fertilization rate was estimated at 5.4%, with considerable variability between genotypes (from 0% to 26%). These findings are useful to formulate recommendations for seed orchard management (seed orchard location, soil and climate optimal conditions, minimum age for commercial seed lots harvesting) and for identifying new research perspectives (exploring links between pollen contamination and climatic data, genetic control of flowering traits).

genetics↗

bioRxiv2019

Genetic diversity and structure of sweet chestnut (Castanea sativa Mill.) in France: At the intersection between Spain and Italy

ContextRenewed interest in European chestnut in France is focused on finding locally adapted populations partially resistant to ink disease and identifying local landraces. AimsWe genotyped trees to assess (i) the genetic diversity of wild and cultivated chestnut across most of its range in France, (ii) their genetic structure, notably in relation with the sampled regions, and (iii) relations with its neighbors in Spain and Italy. MethodsA total of 693 trees in 16 sampling regions in France were genotyped at 24 SSRs, and 1,401 trees in 17 sampling regions at 13 SSRs. ResultsGenetic diversity was high in most sampling regions, with redundancy between them. No significant differentiation was found between wild and cultivated chestnut. A genetic structure analysis with no a priori information found a low, yet significant structure, and identified two clusters. One cluster gathers trees from south-east France and Corsica (RPP1) and another cluster gathers trees from all other sampled regions (RPP2). A substructure was detected at 13 SSRs suggesting differentiation within both RPP1 and RPP2. RPP1 was split between south-east France and Corsica. RPP2 was split between north-west France, Aveyron, Pyrenees and a last cluster gathering individuals from several other regions. ConclusionThe genetic structure within and between our sampling regions is likely the result of natural events (recolonization after the last glaciation) and human activities (migration and exchanges). Notably, we provide evidence for a common origin of most French and Iberian chestnut trees, except those from south-east France that were associated with the Italian gene pool. This advances our knowledge of chestnut genetic diversity and structure, will benefit conservation and help our local partners valorization efforts.

genetics↗