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We argue that the need for a quality seed supply chain is a major bottleneck for the restoration of Chile's native ecosystems, thus supplementing the list of bottlenecks proposed by Bannister et al. in 2018. Specifically, there is a need for defining seed transfer zones, developing standards and capacities for properly collecting and storing seeds, reducing information gaps on seed physiology and longevity, and implementing an efficient seed supply chain with certification of seed origin and quality. Without such capacities, countries are unlikely to meet their restoration commitments. Although we focus on bottlenecks in Chile, the issues we raise are relevant to other countries and thus the global agenda for ecological restoration.

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From anthesis to mature seed formation, burrs from cross-pollinated adult Castanea sativa Miller trees were characterized and seven developmental stages defined based on macro and micromorphological traits. In order to get an insight into the involvement of epigenetic mechanisms in sexual embryogenesis and to define somatic embryogenesis induction capability, global DNA methylation and the somatic embryogenic competence were quantified. On cross-pollinated trees once fertilization takes place, at least one ovule per ovary becomes dominant, and transient DNA demethylation occurs coinciding with the start of the sexual embryogenic programme. Unfertilized ovules from the same cluster, which maintain their prior size, increase their methylation level and undergo degeneration. These results were validated using non-cross-pollinated trees and the asynchrony of flower receptivity. When testing in vitro somatic embryogenesis response of isolated dominant ovules and axes from zygotic embryos under cross-pollinated conditions, the highest competence was found for reaching seed maturity. Thus, a "developmental window" of somatic embryogenesis in chestnut has been characterized. It includes from fertilization to embryo maturity, and a transient decrease in methylation is necessary after fertilization for the development of the somatic embryogenesis response.

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