International Scientific Journal on Reforestation, Afforestation and Tree Reproduction
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Issue 21, 2026

Online ISSN: 2466-4367

, Issue 21, (2026)

Published: 22.01.2026.

Open Access

This Special Issue of Reforesta, International Practices for Regenerating and Restoring Forest Trees by Seeding, brings together regional practice and research from North America, South America, Europe, Asia, and Oceania on using broadcast and direct seeding to create forest cover. It presents a significant range of seeding activities inclusive of species, forests, sites, and climates. Seeding has regained interest because of its scalability and cost-effectiveness, particularly for remote or inaccessible areas, sites with low productivity where planting seedling costs are prohibitive, or when aiming for a more natural forest structure. Technological innovations, particularly in seed treatments, automation, and precision seeding improve success of large-scale seed dispersal.

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01.12.2024.

Research paper

Lethals can be estimated from doubled haploid <i>Larix decidua </i>female gametophytes
We present a novel way of estimating embryo lethals using doubled haploid (dihaploid or DH) female gametophytes grown in tissue culture. This DH-based lethals estimate is hypothesized to be lower than the more common method where lethals are estimated from one generation of selfing. The chief reasoning is the early mortality spike observed for selfed embryos of larch and other genera in the Pinaceae. This early mortality spike occurs at the stage when diploid embryos embed into haploid female gametophyte tissue. However, this stage is missing for DH embryos which grow in a petri dish thus the DH lethals estimate is hypothesized to be lower compared to seed counts. This DH estimate is based on 20,000 haploid female gametophytes cultures from which two surviving diploidized embryos were recovered. Lethals based on diploidized haploids (DH) have not been reported for a conifer previously because, aside from larch, only a few conifer species continue female gametophyte development in absence of pollen. Our chief finding is that, contrary to our hypothesis, the DH-based lethals estimate was similar to lethals estimated obtained from selfed seeds in published studies. Thus doubling haploid female gametophytes can be used to estimate embryo lethals when diploidization is conducted on a massive scale.

Claire Williams, Patrick Von Aderkas

01.12.2024.

Research paper

Gametophytic apomixis in a gymnosperm, Larix decidua Mill., results in normal male meiosis
An adult tree of Larix decidua Mill., European larch, was produced from doubling one haploid female gametophyte. Whether this tree can produce normal male meiocytes is the crucial question. This adult’s pollen mother cells (PMCs), or male meiocytes, were squashed and stained. Male meiosis was normal and no abortive pollen grains were observed. This female gametophytic apomict of a conifer, a dihaploid adult, is 100% homozygous yet also reproductively competent with normal male meiosis and functional male pollen. Here we show that doubled female gametophytes can produce embryos and reproductively competent adult trees. This shows a way to gain rapid homozygosity and produce completely inbred lines for larch. This is a novel breeding shortcut reported for the first time for a conifer species.

Patrick Von Aderkas, Claire Williams