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Nickel is a crucial metal widely used in various industrial applications, such as lithium‐ion batteries and stainless‐steel production. The increasing demand for nickel and resource depletion challenges highlight the need for sustainable extraction methods. Agromining employs hyperaccumulator plants to extract nickel from soils that are either contaminated or naturally enriched in nickel. Bornmuellera emarginata is a nickel hyperaccumulator originating from Greece and a promising candidate for nickel agromining. This study aimed to identify suitable genotypes for a successful "domestication" breeding program, focusing on phenotypic traits. Seeds from 35 plants across six wild populations were cultivated under controlled conditions for 7 months to complete a full life cycle. In this period, growth parameters (e.g., plant height (PH), leaf size, and biomass) were determined. Geographically proximate populations displayed greater phenotypic similarity than those from distant locations. Substantial morphological variations, including PH (40–126 cm) and leaf length (6–13 cm), were observed. Nickel concentrations in plants ranged from 290 to 6250 mg kg−1 dry weight, resulting in nickel yields of 10–145 mg/plant. The notable phenotypic differences among genotypes provide a valuable biological resource for initiating a breeding program to enhance overall nickel yield in B. emarginata agromining crops. Selection and breeding efforts should prioritize genotypes with high biomass production and nickel concentrations. This research lays the foundation for targeted breeding to optimize the potential of B. emarginata in nickel agromining. [ABSTRACT FROM AUTHOR]

The 10th International Conference on Serpentine Ecology was held in Nancy, France on June 12–16, 2023. The main goals of the conference were to create a platform for the exchange of ideas and experiences and to promote scientific dialogue among scientists from numerous fields who share expertise in the study of ultramafic habitats worldwide. The proceedings of the conference are being published as two Special Issues of Ecological Research, of which this is the second. In this article, we present the major topics and provide some highlights of the contributions to the 10th International Conference on Serpentine Ecology. [ABSTRACT FROM AUTHOR]

Agromining describes the technique of growing plants to "mine" metals present in naturally enriched or contaminated soils. This technique comprises a series of processes including improvement of soil quality and production of biomass in order to obtain metals from the ash of harvested hyperaccumulators, which can be considered bio‐ore. The aim of this study was to evaluate different agronomic practices for Ni agromining of the hyperaccumulator species Odontarrhena chalcidica by analyzing (i) Ni yields and (ii) parameters related to soil fertility, biodiversity, and Ni availability. We tested various types of fertilizers including farmyard manure and assessed cultivation of the hyperaccumulator in either continuous monoculture or cropping in rotation with the legume Vicia ervilia. A 2‐year field experiment was established on typical ultramafic Vertisols in eastern Albania. The current study presents the results obtained in the second year of cultivation. After 2 years of agromining, fertilization with animal manure or rotation with the legume improved several soil properties and increased the yield of phytoextracted Ni by four and five times, respectively, relative to non‐fertilized plots. The fertilization treatments did not affect the bacterial diversity indexes but significantly impacted the bacterial community structure. We suggest a fertilization regime including the application of pig or chicken manure (at doses equivalent to NPK 260:105:260; 260:390:260, respectively) every 2 years or the implementation of crop rotation with legumes as effective strategies for developing Ni agromining on Vertisols. [ABSTRACT FROM AUTHOR]

Hyperaccumulators are unusual plants that accumulate specific metals or metalloids in their living tissues to concentrations that may be hundreds or thousands of times greater than those normal for most plants. Hyperaccumulator plants are of practical importance as they can be used in soil remediation technologies. The Shebenik Mountain massif, located on the eastern border of Albania, hosts a wide diversity of rare and endemic plant species, including nickel hyperaccumulators. The aim of this study was to evaluate the taxa present on the Shebenik Mt. in relation to soil conditions and to test their potential for phytomining in a replicated field trial. Previous morphological and karyological analyses of material from field collections across ultramafic outcrops of the Shebenik resulted in the identification of the following nickel hyperaccumulator taxa: Odontarrhena chalcidica (Janka) Španiel & al., Odontarrhena smolikana subsp. glabra (Nyár.) Španiel & al., Odontarrhena rigida (Nyár.) L. Cecchi & Selvi, and Bornmuellera baldaccii (Degen) Heywood. In addition, a species of the genus Noccaea, formerly referred to Noccaea ochroleuca (Boiss. & Heldr.) F.K. Mey, but likely belonging to a still undescribed taxon, was also collected. An in situ replicated trial was undertaken to evaluate the potential for phytomining of three nickel (Ni) hyperaccumulators collected in the Shebenik Mt. Measurement of aboveground biomass, analysis of nickel in the biomass, and analyses of plant‐available nickel in the soil allowed calculation of bioaccumulation and phytoextraction yield. This provides a realistic evaluation of the efficacy of the plant taxa in hyperaccumulating nickel and their potential use for phytoextraction/phytomining technologies. [ABSTRACT FROM AUTHOR]

Research on metal hyperaccumulating plants has concentrated on New Caledonia, Brazil, Cuba, the Mediterranean basin, and southeastern Asia, while other regions remain under studied. This work used a systematic approach in the targeted search for new hyperaccumulators in Mesoamerica, with a focus on characterizing nickel (Ni) hyperaccumulation in six species of Orthion and the monotypic genus Mayanaea (Violaceae), to complement earlier global studies on the related genus Hybanthus. We screened major herbarium collections, using x‐ray fluorescence (XRF) analysis to measure metal concentrations in specimens of Orthion and Mayanaea ranging from Mexico to Nicaragua. In addition, fresh samples collected in Mexico were analyzed with associated rhizosphere soils. The results indicated that all species of Orthion and Mayanaea are able to hyperaccumulate Ni. Ni concentration ranges in leaves of herbarium specimens were (in mg kg−1 dry weight): Orthion guatemalense (380–5100), O. malpighiifolium (24–5620), O. montanum (1620–5850), O. oblanceolatum (60–1440), O. subsessile (450–18,700), and O. veracruzense (22–3660). The available specimen of Mayanaea caudata had foliar Ni concentration of 5390 mg kg−1. Field‐collected samples of O. veracruzense and O. subsessile had similar Ni concentrations to herbarium specimens. Additionally, many Orthion species were facultative hyperaccumulators of cobalt. This is the first report of Ni hyperaccumulation in Violaceae from the Western Hemisphere. Ni hyperaccumulation in Orthion and Mayanaea is consistent with published phylogenies showing that they belong to a clade which also includes strong hyperaccumulators in the genus Hybanthus from Australia and New Caledonia. Orthion subsessile has suitable traits to become a potential crop for agromining of Ni. [ABSTRACT FROM AUTHOR]

Until 2019, there were no published reports of trace element hyperaccumulation in the plants of Central America or Mexico. Recent reports, based mostly on measurement of herbarium specimens using x‐ray fluorescence (XRF) spectroscopy, have begun to identify hyperaccumulators of nickel (Ni) in this region. The most extensive deposits of Ni‐rich ultramafic rocks and soils in Central America occur along the Polochic‐Motagua fault system in eastern Guatemala. This study focused on discovery and characterization of new hyperaccumulators in Guatemala, starting with surveys of herbarium specimens, followed by field studies to understand the ultramafic soils of the region and the ecology of hyperaccumulators that occur there. Initial XRF screening at the Missouri Botanical Garden Herbarium, along with two herbaria in Guatemala, identified four previously unreported Ni hyperaccumulators—Arachnothryx linguiformis, Arachnothryx buddleioides, Chionanthus panamensis, and Orthion guatemalense. Field studies in Guatemala characterized the communities in which these species occur, some of which include multiple hyperaccumulator species growing in close proximity. In two taxa that showed phenotypic variation in foliar Ni concentration, there was no statistically significant correlation between Ni concentrations in leaves and either the total or DTPA‐extractable Ni in soils, suggesting that other genetic or environmental variables may influence hyperaccumulation. [ABSTRACT FROM AUTHOR]

A new species of Odontarrhena (Brassicaceae) is described from Mount Vourinos in western Macedonia, Greece. The species is restricted to the ridge and the northern slopes of Mt. Vourinos above 1500 m a.s.l. and grows on stony slopes and dry rocky grassland on ultramafic soil with elevated trace metal concentrations. Based on morphological, karyological, and nrDNA sequences, the species is tetraploid with supernumerary B‐chromosomes (2n = 4× = 32 + 2B) and related to the Balkan endemic Odontarrhena decipiens. It differs from the latter mainly by the habit of subshrub with woody base and a denser indumentum of stellate trichomes, resulting in a white‐silvery color of the leaves and shoots. The presence of four degenerate positions in the ITS1 region was detected only in the new species from Mt. Vourinos. Shoot Ni concentrations determined by x‐ray fluorescence analysis and atomic absorption spectroscopy were largely variable (6200–18,700 μg g−1 dw), but always significantly higher than in roots. Hydroponic trials confirmed the typical features of Ni hyperaccumulating plants, such as growth stimulating effect at low metal doses and shoot metal concentration above the hyperaccumulation threshold. The new species of Odontarrhena is a Ni hyperaccumulator with substantial aboveground biomass production, making it a promising candidate for phytomining applications. [ABSTRACT FROM AUTHOR]