Forest creation has the potential to reduce biodiversity loss and mitigate climate change but, tree disease emergence may counteract this. Further, given decadal timescales required for forest establishment, climate change is increasingly likely to act as a filter on plant community assembly. In the temperate lowlands succession takes 30 to 50 years for non-forest land to establish woodland plant assemblages, while the timescales required for new forest to sequester carbon suggest unassisted succession will be too slow for net zero 2050 targets. However, if plantations can establish faster than succession it would be beneficial to recommend planting native species as soon as possible. We explore scenarios of broadleaved woodland development across Wales, UK, as a case study area. We use a suite of empirical species niche models for British plants to estimate the potential species composition of forests with, and without, projected climate change. Additionally, we examine how tree canopy composition alters if Fraxinus excelsior is widely impacted by ash-dieback ( Hymenoscyphus fraxineus ). The results suggest soil total carbon and nitrogen could achieve baseline broadleaved forest values in less than 30 years. However only timber and woody flora species groups showed diversity surpassing baseline broadleaved forest diversity, with nectar plants and ancient woodland indicator species failing to reach baseline equivalents within 30 years; although complete congruence is unlikely given baseline forests could be hundreds of years old. Where Fraxinus excelsior was removed from the species pool we predicted that a scrub phase will persist or, if present, Acer pseudoplatanus will become the canopy dominant. The heavier shade cast this species is likely to result in differences in species composition of the understory and ground flora diversity is likely to decrease. Reliance on unassisted succession will also depend critically on (a) dispersal from local source populations and (b) on establishment filters that could be severe in landscapes with high management intensity history. These findings indicate that leaving the UK’s fragmented habitats to relying on already degraded successional processes could lead to poor afforestation outcomes. Highlights Afforestation can mitigate global change but tree disease makes outcomes uncertain Afforestation methods establishment timescales and time for benefits to occur We model afforestation and predict how soils and plants change with climate Ash loss from die-back is replaced by low low-canopy woodland / scrub over 30 years Afforestation achieves baseline forest values for some variables within 30 years

[This corrects the article DOI: 10.1093/conphys/coab099.].

Loss of sexual reproductive capacity has been proposed as a syndrome of domestication in vegetatively propagated crops, but there are relatively few examples from agricultural systems. In this study, we compare sexual reproductive capacity in wild (sexual) and domesticated (vegetative) populations of enset (Ensete ventricosum (Welw.) Cheesman), a tropical banana relative and Ethiopian food security crop. We examined floral and seed morphology and germination ecology across 35 wild and domesticated enset. We surveyed variation in floral and seed traits, including seed weight, viability and internal morphology, and germinated seeds across a range of constant and alternating temperature regimes to characterize optimum germination requirements. We report highly consistent floral allometry, seed viability, internal morphology and days to germination in wild and domesticated enset. However, seeds from domesticated plants responded to cooler temperatures with greater diurnal range. Shifts in germination behaviour appear concordant with a climatic envelope shift in the domesticated distribution. Our findings provide evidence that sexual reproductive capacity has been maintained despite long-term near-exclusive vegetative propagation in domesticated enset. Furthermore, certain traits such as germination behaviour and floral morphology may be under continued selection, presumably through rare sexually reproductive events. Compared to sexually propagated crops banked as seeds, vegetative crop diversity is typically conserved in living collections that are more costly and insecure. Improved understanding of sexual propagation in vegetative crops may have applications in germplasm conservation and plant breeding.

Collection and storage of crop wild relative (CWR) germplasm is crucial for preserving species genetic diversity and crop improvement. Nevertheless, much of the genetic variation of CWRs is absent in ex situ collections and detailed passport data are often lacking. Here, we focussed on Musa balbisiana, one of the two main progenitor species of many banana cultivars. We investigated the genetic structure of M. balbisiana across its distribution range using microsatellite markers. Accessions stored at the International Musa Germplasm Transit Centre (ITC) ex situ collection were compared with plant material collected from multiple countries and home gardens from Vietnam. Genetic structure analyses revealed that accessions could be divided into three main clusters. Vietnamese and Chinese populations were assigned to a first and second cluster respectively. A third cluster consisted of ITC and home garden accessions. Samples from Papua New Guinea were allocated to the cluster with Chinese populations but were assigned to a separate fourth cluster if the number of allowed clusters was set higher. Only one ITC accession grouped with native M. balbisiana populations and one group of ITC accessions was nearly genetically identical to home garden samples. This questioned their wild status, including accessions used as reference for wild M. balbisiana. Moreover, most ITC accessions and home garden samples were genetically distinct from wild populations. Our results highlight that additional germplasm should be collected from the native distribution range, especially from Northeast India, Myanmar, China, and the Philippines and stored for ex situ conservation at the ITC. The lack of passport data for many M. balbisiana accessions also complicates the interpretation of genetic information in relation to cultivation and historical dispersal routes.

Northern Viet Nam displays a remarkable diversity of wild bananas (Musa L.), including the species from which the majority of cultivated bananas derive. The taxonomy and exact distribution of these wild bananas are however not well known, limiting their conservation and use. In the present study, we describe the morphology, ecology, and phytogeography of the 6 Musa species that were collected between 2016 and 2019 in northern Viet Nam: Musa acuminata Colla, M. balbisiana Colla, M. itinerans Cheesman, M. haekkinenii N.S.Ly & Haev, M. lutea R.V.Valmayor, L.D.Danh and Hakkinen and M. paracoccinea A.Z.Liu and D.Z.Li:. Of these, M. itinerans was the species with the most widespread distribution range, occurring as large mats in various habitats between 136 and 1331 m, whereas M. acuminata was found between 136 and 989 m and M. balbisiana was between 108 and 981 m. Furthermore, M. lutea, M. paracoccinea and M. haekkinenii were distributed in open areas with low competition for light, between 80 and 800 m. These latter three species have the potential to become ornamental plants, being characterized by bright and colourful upright inflorescences. The data presented here will help in providing a valuable contribution to the conservation and use of the wild bananas in northern Viet Nam.

[This corrects the article DOI: 10.1093/conphys/coab099.].

Crop wild relatives (CWR) are an indispensable source of alleles to improve desired traits in related crops. While knowledge on the genetic diversity of CWR can facilitate breeding and conservation strategies, it has poorly been assessed. Cultivated bananas are a major part of the diet and income of hundreds of millions of people and can be considered as one of the most important fruits worldwide. Here, we assessed the genetic diversity and structure of Musa balbisiana, an important CWR of plantains, dessert and cooking bananas. Musa balbisiana has its origin in subtropical and tropical broadleaf forests of northern Indo-Burma. This includes a large part of northern Vietnam where until now, no populations have been sampled. We screened the genetic variation and structure present within and between 17 Vietnamese populations and six from China using 18 polymorphic SSR markers. Relatively high variation was found in populations from China and central Vietnam. Populations from northern Vietnam showed varying levels of genetic variation, with low variation in populations near the Red River. Low genetic variation was found in populations of southern Vietnam. Analyses of population structure revealed that populations of northern Vietnam formed a distinct genetic cluster from populations sampled in China. Together with populations of central Vietnam, populations from northern Vietnam could be subdivided into five clusters, likely caused by mountain ranges and connected river systems. We propose that populations sampled in central Vietnam and on the western side of the Hoang Lien Son mountain range in northern Vietnam belong to the native distribution area and should be prioritised for conservation. Southern range edge populations in central Vietnam had especially high genetic diversity, with a high number of unique alleles and might be connected with core populations in northern Laos and southwest China. Southern Vietnamese populations are considered imported and not native.

1. Ecologically meaningful seed germination experiments are constrained by access to seeds and relevant environments for testing at the same time. This is particularly the case when research is carried out far from the native area of the studied species. 2. Here, we demonstrate an alternative - the use of glass houses in botanic gardens as simulated-natural habitats to extend the ecological interpretation of germination studies. Our focal taxa were banana crop wild relatives (Musa acuminata subsp. burmannica, M. acuminata subsp. siamea and M. balbisiana), native to tropical and subtropical Southeast Asia. Tests were carried out in Belgium, where we performed germination tests in relation to exposure to sun and foliage-shading, seed burial-depth in different heated glass house compartments, as well as seed survival and dormancy release in the soil. We anchored the interpretation of these studies by also conducting an experiment in a semi-natural habitat in the species native range (M. balbisiana - Los Baños, the Philippines), where we tested germination responses to exposure to the sun and shade. Using temperature data loggers, we determined temperature dynamics suitable for germination in both these settings. 3. In semi-natural and simulated-natural habitats, seeds germinated in response to exposure to direct solar radiation. Seed burial-depth had a significant but marginal effect by comparison, even when seeds were buried to 7cm in the soil. Temperatures at sun-exposed compared to shaded environments differed by only a few degrees Celsius. Maximum temperature of the period prior to germination was the most significant contributor to germination responses and germination increased linearly above a threshold of 23°C to the maximum temperature in the soil (in simulated natural habitats) of 35°C. 4. Glass houses can provide useful environments to aid interpretation of seed germination responses to environmental niches.

Abstract Ecologically meaningful seed germination experiments are constrained by access to seeds and relevant environments for testing at the same time. This is particularly the case when research is carried out far from the native area of the studied species. Here, we demonstrate an alternative—the use of glasshouses in botanic gardens as simulated‐natural habitats to extend the ecological interpretation of germination studies. Our focal taxa were banana crop wild relatives (Musa acuminata subsp. burmannica, Musa acuminata subsp. siamea, and Musa balbisiana), native to tropical and subtropical South‐East Asia. Tests were carried out in Belgium, where we performed germination tests in relation to foliage‐shading/exposure to solar radiation and seed burial depth, as well as seed survival and dormancy release in the soil. We calibrated the interpretation of these studies by also conducting an experiment in a seminatural habitat in a species native range (M. balbisiana—Los Baños, the Philippines), where we tested germination responses to exposure to sun/shade. Using temperature data loggers, we determined temperature dynamics suitable for germination in both these settings. In these seminatural and simulated‐natural habitats, seeds germinated in response to exposure to direct solar radiation. Seed burial depth had a significant but marginal effect by comparison, even when seeds were buried to 7 cm in the soil. Temperatures at sun‐exposed compared with shaded environments differed by only a few degrees Celsius. Maximum temperature of the period prior to germination was the most significant contributor to germination responses and germination increased linearly above a threshold of 23℃ to the maximum temperature in the soil (in simulated‐natural habitats) of 35℃. Glasshouses can provide useful environments to aid interpretation of seed germination responses to environmental niches.

Since natural habitats are disappearing fast, there is an urgent need to collect, characterize, and phenotype banana (Musa spp.) crop wild relatives to identify unique genotypes with specific traits that fill the gaps in our gene banks. We report on a collection mission in Papua New Guinea carried out in 2019. Seed containing bunches were collected from Musa peekelii ssp. angustigemma (N.W.Simmonds) Argent (3), M. schizocarpa N. W. Simmonds (4), M. balbisiana Colla (3), M. acuminata ssp. banksii (F. Muell.) Simmonds (14), M. boman Argent (3), M. ingens Simmonds (2), M. maclayi ssp. maclayi F.Muell. ex Mikl.-Maclay (1), and M. lolodensis Cheesman (1). This material, together with the seeds collected during a previous mission in 2017, form the basis for the development of a wild banana seed bank. For characterization and phenotyping, we focused on the most ubiquitous indigenous species of Papua New Guinea: M. acuminata ssp. banksii, the ancestor of most edible bananas. We calculated that the median genomic dissimilarity of the M. acuminata ssp. banksii accessions was 4% and that they differed at least 5% from accessions present in the International Transit Centre, the world's largest banana gene bank. High-throughput phenotyping revealed drought avoidance strategies with significant differences in root/shoot ratio, soil water content sensitivity, and response towards vapor pressure deficit (VPD). We deliver a proof of principle that the wild diversity is not yet fully covered in the gene banks and that wild M. acuminata ssp. banksii populations contain individuals with unique traits, useful for drought tolerance breeding programs.

Abstract Storing seed collections of crop wild relatives, wild plant taxa genetically related to crops, is an essential component in global food security. Seed banking protects genetic resources from degradation and extinction and provides material for use by breeders. Despite being among the most important crops in the world, banana and plantain crop wild relatives are largely under‐represented in genebanks. Nevertheless, banana crop wild relative seed collections are in fact held in different countries, but these have not previously been part of reporting or analysis. To fill this gap, we firstly collated banana seed accession data from 13 institutions in 10 countries. These included 537 accessions containing an estimated 430,000 seeds of 56 species. We reviewed their taxonomic coverage and seed storage conditions including viability estimates. We found that seed accessions have low viability (25% mean) representing problems in seed storage and processing. Secondly, we surveyed 22 institutions involved in banana genetic resource conservation regarding the key constraints and knowledge gaps that institutions face related to banana seed conservation. Major constraints were identified including finding suitable material and populations to collect seeds from, lack of knowledge regarding optimal storage conditions and germination conditions. Thirdly, we carried out a conservation prioritization and gap analysis of Musaceae taxa, using established methods, to index representativeness. Overall, our conservation assessment showed that despite this extended data set banana crop wild relatives are inadequately conserved, with 51% of taxa not represented in seed collections at all; the average conservation assessment showing high priority for conservation according to the index. Finally, we provide recommendations for future collecting, research, and management, to conserve banana and plantain crop wild relatives in seed banks for future generations.

Seed banks were first established to conserve crop genetic diversity, but seed banking has more recently been extended to wild plants, particularly crop wild relatives (CWRs) (e.g., by the Millennium Seed Bank (MSB), Royal Botanic Gardens Kew). CWRs have been recognised as potential reservoirs of beneficial traits for our domesticated crops, and with mounting evidence of the importance of the microbiome to organismal health, it follows that the microbial communities of wild relatives could also be a valuable resource for crop resilience to environmental and pathogenic threats. Endophytic fungi reside asymptomatically inside all plant tissues and have been found to confer advantages to their plant host. Preserving the natural microbial diversity of plants could therefore represent an important secondary conservation role of seed banks. At the same time, species that are reported as endophytes may also be latent pathogens. We explored the potential of the MSB as an incidental fungal endophyte bank by assessing diversity of fungi inside stored seeds. Using banana CWRs in the genus Musa as a case-study, we sequenced an extended ITS-LSU fragment in order to delimit operational taxonomic units (OTUs) and used a similarity and phylogenetics approach for classification. Fungi were successfully detected inside just under one third of the seeds, with a few genera accounting for most of the OTUs–primarily Lasiodiplodia , Fusarium , and Aspergillus –while a large variety of rare OTUs from across the Ascomycota were isolated only once. Fusarium species were notably abundant–of significance in light of Fusarium wilt, a disease threatening global banana crops–and so were targeted for additional sequencing with the marker EF1α in order to delimit species and place them in a phylogeny of the genus. Endophyte community composition, diversity and abundance was significantly different across habitats, and we explored the relationship between community differences and seed germination/viability. Our results show that there is a previously neglected invisible fungal dimension to seed banking that could well have implications for the seed collection and storage procedures, and that collections such as the MSB are indeed a novel source of potentially useful fungal strains.

Abstract Background Conservation of plant genetic resources, including the wild relatives of crops, plays an important and well recognised role in addressing some of the key challenges faced by humanity and the planet including ending hunger and biodiversity loss. However, the genetic diversity and representativeness of ex situ collections, especially that contained in seed collections, is often unknown. This limits meaningful assessments against conservation targets, impairs targeting of future collecting and limits their use. We assessed genetic representation of seed collections compared to source populations for three wild relatives of bananas and plantains. Focal species and sampling regions were M. acuminata subsp. banksii (Papua New Guinea), M. balbisiana (Viet Nam) and M. maclayi s.l. (Bougainville, Papua New Guinea). We sequenced 445 samples using suites of 16–20 existing and newly developed taxon-specific polymorphic microsatellite markers. Samples of each species were from five populations in a region; 15 leaf samples from different individuals and 16 seed samples from one infructescence (‘bunch’) were analysed for each population. Results Allelic richness of seeds compared to populations was 51, 81 and 93% (M. acuminata, M. balbisiana and M. maclayi respectively). Seed samples represented all common alleles in populations but omitted some rarer alleles. The number of collections required to achieve the 70% target of the Global Strategy for Plant Conservation was species dependent, relating to mating systems. Musa acuminata populations had low heterozygosity and diversity, indicating self-fertilization; many bunches were needed (> 15) to represent regional alleles to 70%; over 90% of the alleles from a bunch are included in only two seeds. Musa maclayi was characteristically cross-fertilizing; only three bunches were needed to represent regional alleles; within a bunch, 16 seeds represent alleles. Musa balbisiana, considered cross-fertilized, had low genetic diversity; seeds of four bunches are needed to represent regional alleles; only two seeds represent alleles in a bunch. Conclusions We demonstrate empirical measurement of representation of genetic material in seeds collections in ex situ conservation towards conservation targets. Species mating systems profoundly affected genetic representation in seed collections and therefore should be a primary consideration to maximize genetic representation. Results are applicable to sampling strategies for other wild species.

Ex situ seed conservation of banana crop wild relatives (Musa spp. L.), is constrained by critical knowledge gaps in their storage and germination behaviour. Additionally, challenges in collecting seeds from wild populations impact the quality of seed collections. It is, therefore, crucial to evaluate the viability of seeds from such collecting missions in order to improve the value of future seed collections. We evaluate the seed viability of 37 accessions of seven Musa species, collected from wild populations in Papua New Guinea, during two collecting missions. Seeds from one mission had already been stored in conventional storage (dried for four months at 15% relative humidity, 20 °C and stored for two months at 15% relative humdity, −20 °C), so a post-storage test was carried out. Seeds from the second mission were assessed freshly extracted and following desiccation. We used embryo rescue techniques to overcome the barrier of germinating in vivo Musa seeds. Seeds from the first mission had low viability (19 ± 27% mean and standard deviation) after storage for two months at 15% relative humidity and −20 °C. Musa balbisiana Colla seeds had significantly higher post-storage germination than other species (p < 0.01). Desiccation reduced germination of the seeds from the second collecting mission, from 84 ± 22% (at 16.7 ± 2.4% moisture content) to 36 ± 30% (at 2.4 ± 0.8% moisture content). There was considerable variation between and (to a lesser extent) within accessions, a proportion of individual seeds of all but one species (Musa ingens N.W.Simmonds) survived desiccation and sub-zero temperature storage. We identified that seeds from the basal end of the infructescence were less likely to be viable after storage (p < 0.001); and made morphological observations that identify seeds and infructescences with higher viability in relation to their developmental maturity. We highlight the need for research into seed eco-physiology of crop wild relatives in order to improve future collecting missions.

AbstractSeed conservation of banana crop wild relatives (Musa L. spp.) is limited because of lack of knowledge about their germination ecology. Musa acuminata Colla, the most important banana crop wild relative, is distributed in tropical and subtropical Asian and Pacific rainforests and colonizes disturbed sites. The role of temperature in stimulating/inhibiting germination to detect disturbance when canopy gaps are formed is not well known. We assessed seed germination thermal requirements of three subspecies of M. acuminata using nine seed accessions which had been stored in the Millennium Seed Bank. Diurnally alternating temperature cycles were almost completely essential for germination compared with constant temperatures. Germination was optimal when the upper temperature of a diurnal cycle was at 35°C; the lower temperature of the cycle was less important. Subspecies occurrence coordinates were used to extract climate temperature data which were then compared against the temperature requirements for germination from our experiment results. Maximum temperatures of the warmest month across subspecies ranges were close to but below optimal germination temperatures, as were diurnal ranges, suggesting soil-warming at the micro-climate level following gap creation is important for M. acuminata seed germination. Additionally, pre-treatment for 3 months at 60% relative humidity at constant 25°C improved germination from 14 ± 10 (mean, standard deviation) to 41 ± 29% suggesting a period in the soil seed bank under the canopy may increase sensitivity to alternating temperature cycles. Overall viability was low (49 ± 28%), and considerable variance was caused by the different accessions. Germination remained somewhat inconsistent.

BACKGROUNDEnset (Ensete ventricosum, Musaceae) is an African crop that currently provides the staple food for approx. 20 million Ethiopians. Whilst wild enset grows over much of East and Southern Africa and the genus extends across Asia to China, it has only ever been domesticated in the Ethiopian Highlands. Here, smallholder farmers cultivate hundreds of landraces across diverse climatic and agroecological systems.SCOPEEnset has several important food security traits. It grows over a relatively wide range of conditions, is somewhat drought-tolerant, and can be harvested at any time of the year, over several years. It provides an important dietary starch source, as well as fibres, medicines, animal fodder, roofing and packaging. It stabilizes soils and microclimates and has significant cultural importance. In contrast to the other cultivated species in the family Musaceae (banana), enset has received relatively little research attention. Here, we review and critically evaluate existing research, outline available genomic and germplasm resources, aspects of pathology, and explore avenues for crop development.CONCLUSIONEnset is an underexploited starch crop with significant potential in Ethiopia and beyond. Research is lacking in several key areas: empirical studies on the efficacy of current agronomic practices, the genetic diversity of landraces, approaches to systematic breeding, characterization of existing and emerging diseases, adaptability to new ranges and land-use change, the projected impact of climate change, conservation of crop wild relatives, by-products or co-products or non-starch uses, and the enset microbiome. We also highlight the limited availability of enset germplasm in living collections and seedbanks, and the lack of knowledge of reproductive and germination biology needed to underpin future breeding. By reviewing the current state of the art in enset research and identifying gaps and opportunities, we hope to catalyse the development and sustainable exploitation of this neglected starch crop.

Seed banking is an invaluable tool in plant conservation, both as an archive and a source of genetic variation. Despite the increasing focus on the validation of sampling strategies, few studies have empirically related diversity in seed bank collections with variation in wild-provenance populations. By using a set of nuclear microsatellites, we investigated genetic diversity in British populations of Taxus baccata (European yew tree). We used our findings as a baseline for the quantification of genetic diversity captured in the germplasm collections maintained by the Millennium Seed Bank (Royal Botanic Gardens, Kew), in terms of allelic richness and allelic capture. We observed that genetic differentiation in wild populations of yew is compatible with highly effective gene flow, with no geographic patterns. Heterozygosity is lower than expected for a dioecious obligate outbreeder. Seed collections are representative of wild populations in terms of allelic capture, including rare and locally common variants, indicating that the current sampling protocol implemented by the UK National Tree Seed Project is appropriate. Specific sampling strategies might be improved by including more populations at the edge of the range and in remote localities, even at the expense of contiguous populations. Our methods may be applied to evaluate allelic capture in other germplasm collections for which a baseline exists, i.e. in which genetic diversity in the wild-provenance populations is known. Our recommendations related to sampling strategies can be extended to other tree species with continuous distributions and effective gene flow.

Gene conservation programs help safeguard species and tangibly benefit ecological restoration, agriculture, forestry, and horticulture. Here we describe a new method for deciding which and how many populations and individuals to conserve ex situ, and we demonstrate the method by evaluating collections of European Ash (Fraxinus excelsior) for an ongoing seed-banking project, the UK National Tree Seed Project (NTSP). The method uses simulations and geographic distribution data, and does not require (but can utilize) genetic data. We estimate that NTSP collections have captured >90% of all alleles and of locally common alleles. We identified optimal sampling solutions at large and small spatial scales, and for northern isolated vs. southern core populations. We also quantified genetic “points of diminishing returns” with a more precise method than previous studies. This analysis revealed that (for European ash, for a goal of capturing one copy of each allele) an optimal “stopping point” is approximately 35 populations, 10 to 30 trees per population, and 30 seeds per tree. Overall, we conclude that the NTSP protocol of random sampling of at least 15 trees per population from two populations per seed zone is effective. We demonstrated how collectors can adjust the number of populations, individuals and seeds sampled using the concept of “genetic equivalence”, allowing projects to accommodate practical or ecological constraints. Lastly we showed that for a conservation goal of 50 allele copies rather than one copy, a much larger sampling effort is needed (>150 populations). This new approach can be tailored to any species. It is applicable to any seed collection seeking to capture genetic diversity, as well as in situ gene conservation approaches. We emphasize that the ability to quantitatively estimate the outcome of gene conservation activities can help design, justify, or evaluate future programs.