New insights in seed orchards pollen contamination, study case in an advanced breeding program
Pollen contamination and mating structure in maritime pine (Pinus pinaster Ait.) clonal seed orchards revealed by SNP markers
Recommendation: posted 26 July 2023, validated 08 August 2023
Alia, R. (2023) New insights in seed orchards pollen contamination, study case in an advanced breeding program. Peer Community in Forest and Wood Sciences, 100109. 10.24072/pci.forestwoodsci.100109
This preprint (Bouffier et al, 2023) analyses different biological (tree genotype, age, flowering phenology) and environmental factors (vicinity with external pollen sources, orchard structure, soil type, climatic conditions) with influence on the of seed lots in seed orchards of an important forest tree species (Pinus pinaster Ait.). The analysis is based on an optimized set of 60 SNP markers that constitute a new tool for characterizing improved material in the breeding program of the species.
One of the main questions when managing seed orchard is to obtain a precise estimation of pollen contamination, as it causes major losses to genetic improvement from selection and breeding (Di Giovanni and Kevan, 19911) but also will determine the adaptive potential of the species (Kremer et al. 2012). The results indicate that contamination rates were highly variable between seed lots (from 20 to 96%), with a mean value of 50%). The main factors determining these rates include the distance between the seed orchard and external pollen sources, rain during the pollination period, seed orchard age, soil conditions and seed parent identity.
A second point of interest in this paper is the determination of the overall self-fertilization rate. This factor also determines the quality of the seed-lots and was estimated as 5.4%, with high variability between genotypes (from 0% to 26%). The overall value is of the same order of magnitude than in other species.
These results are used to define some recommendations for managing seed orchards in the French breeding program, but that can be generalized to other species (eg. Mullin and Lee, 2013). As an example, they recommend that sampling 100 seeds annually should be sufficient to estimate pollen contamination (with a standard error of 5%). Also, they suggest that one of the main measures to reduce pollen contamination is carefully selecting the location of the orchard, in terms of its distance from external pollen sources and soil conditions, and not collecting seeds from young trees (below 8 years old).
The present preprint revisits an important topic of research with interest for the biology of tree species, but also with great implications in applied breeding activities. The main conclusions are essential to understand the importance of different factors in managing seed orchards and in the future performance of the reproductive material.
In conclusion, this paper stresses the need for more studies, taking advantage of new genomic tools, to advance the knowledge of factors influencing the success of breeding programs.
Bouffier L, Debille S, Alazard P, Raffin A, Pastuszka P, Trontin JF (2023). Pollen contamination and mating structure in maritime pine (Pinus pinaster Ait.) clonal seed orchards revealed by SNP markers. bioRxiv, 2022.09.27.509769, ver. 2 peer-reviewed and recommended by Peer Community in Forest and Wood Science. https://doi.org/10.1101/2022.09.27.509769
Di-Giovanni F, Kevan PG (1991) Factors affecting pollen dynamics and its importance to pollen contamination: a review. Can J For Res 21(8):1155-1170.
Kremer A, Ronce O, Robledo-Arnuncio JJ, Guillaume F, Bohrer G, Nathan R, Bridle JR, Gomulkiewicz R, Klein EK, Ritland K, Kuparinen A, Gerber S, Schueler S (2012) Long-distance gene flow and adaptation of forest trees to rapid climate change. Ecol Lett 15(4):378-92.
Mullin TJ, Lee SJ (2013) Best practice for tree breeding in Europe. Skogforsk, Uppsala, Sweden. ISBN: 530 978-91-977649-6-4. https://www.skogforsk.se/contentassets/42acda01f83843bf925f690bd0a6ed37/best-practice-hela-low.pdf
The recommender in charge of the evaluation of the article and the reviewers declared that they have no conflict of interest (as defined in the code of conduct of PCI) with the authors or with the content of the article. The authors declared that they comply with the PCI rule of having no financial conflicts of interest in relation to the content of the article.
This study was supported by a national grant (QUASEGRAINE project, French Ministry of Agriculture/DGAL, no. 2014-352, coordinated by ONF/B. Musch) and regional funds from the Conseil Régional d’Aquitaine (IMAF project, no. 12009468-052, coordinated by FCBA/L. Harvengt) and the Conseil Régional Centre Val de Loire (IMTEMPERIES project, no. 2014-00094511, coordinated by INRAE/M.-A. Lelu-Walter). We thank Vilmorin and Forelite for providing access to the orchards and the Maritime Pine Breeding Cooperative (GIS Groupe Pin Maritime du Futur) for its support through the FORTIUS project (grants from the Conseil Régional d’Aquitaine and the French Ministry of Agriculture, coordinated by INRAE/P. Pastuszka)
Evaluation round #1
DOI or URL of the preprint: https://doi.org/10.1101/2022.09.27.509769
Version of the preprint: 1
Author's Reply, 21 Jun 2023
Decision by Ricardo Alia, posted 17 Feb 2023, validated 17 Feb 2023
The paper covers a very interesting topic for managing seed orchards, and the extensive study is highly relevant for the area of research. As one of the reviewers points out, there are minor suggestions to improve the manuscript, dealing with a more detailed description of objectives and reducing the discussion. But the quality of the research and writing allows the acceptance of this manuscript.