Institut für Tropische Agrarwissenschaften (Hans-Ruthenberg-Institut)

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A low-tech approach to mobilize nutrients from organic residues to produce bioponic stock solutions
(2024) Heintze, Sebastian; Beckett, Marc; Kriem, Lukas Simon; Germer, Jörn; Asch, Folkard; Liu, Guodong
Organic residues, as a nutrient source suitable of producing solutions for hydroponic crop production, have the potential to reduce the dependence on mineral fertilizers. Especially in remote and resource-constrained regions, organic residues might be the only option to produce hydroponic nutrient solutions. However, nutrient solutions made from organic residues, called bioponic solutions, are usually unbalanced in their nutrient composition, which leads to deficiencies and poor plant growth. This study aimed to experimentally develop a low-tech approach to produce bioponic stock solutions rich in NO3−, P, and K, to create a balanced bioponic solution. The mixed bioponic solution contained 58 mg L−1 NH4+-N, 43 mg L−1 NO3−-N, 50 mg L−1 PO43−-P, and 246 mg L−1 K+. This approach resulted in satisfactory levels of P, K and micronutrients. The solution was tested pure and spiked with Ca(NO3)2 on lettuce in comparison with a mineral Hoagland nutrient solution. Neither the bioponic nor the spiked bioponic solution achieved comparable lettuce yields to the Hoagland solution. The poor growth of the plants in the bioponic solution was attributed to an unfavorable NH4+:NO3− ratio, high microorganism load, and elevated pH levels. However, the approach of preparing bioponic stock solutions could be promising for future research into the production of balanced bioponic nutrient solutions from organic residues.
Abundance and symbiotic efficiency of indigenous rhizobia nodulating faba bean and common bean in southern Ethiopia
(2025) Geremu, Tadele; Abera, Girma; Lemma, Bekele; Rasche, Frank
The symbiotic association between legumes and indigenous rhizobia is crucial for enhancing legume productivity. However, inconsistent results and suboptimal performance of rhizobia inoculation in promoting legume production have been observed. In this regard, we assessed the abundance and symbiotic efficiency of indigenous rhizobia nodulating faba bean and common bean, as well as the soil factors affecting rhizobia abundance in southern Ethiopia. The study also compared the performance of indigenous rhizobia with commercial strains and mineral nitrogen treatment plants. A total of 132 soil samples were collected from barley, wheat, maize, potato, common bean, faba bean, intercropped common bean and maize, enset, and grazing land. Indigenous rhizobia were isolated and enumerated from these samples. Faba bean (FB) and common bean (CB) rhizobia population ranged from 0.0 to 1.7 x 10 4 and 1.7 x 10 1 to 1.7 x 10 7 cells g -1 soil, respectively. Rhizobia populations were significantly influenced by soil pH, EC, OC, TN, CEC, exchangeable acidity, aluminium, and the host crop occurrence. The isolated indigenous rhizobia demonstrated significant potential in enhancing nodulation, shoot dry weight, and TN accumulation in plants. Symbiotic efficiency indices revealed that over 95% of the indigenous rhizobia were effective in nodulation and shoot dry matter accumulation, indicating that naturally occurring rhizobia are efficient and may reduce the need for commercial inoculants in areas with abundant indigenous populations. However, in areas where rhizobia populations are low, strains isolated from faba bean (33FB, 84FB) and common bean (44CB, 102CB), which outperformed commercial strains should be further evaluated. The results suggest that soil rhizobia population levels should be assessed prior to inoculation to optimize nodulation and crop performance. To this end, it is emphasized to evaluate soil rhizobia strains to assess their stability and competitiveness relative to commercial inoculants across different agroecological conditions.
Arbuscular mycorrhizal fungi-based bioremediation of mercury: insights from zinc and cadmium transporter studies
(2023) Guo, Yaqin; Martin, Konrad; Hrynkiewicz, Katarzyna; Rasche, Frank
Phytoremediation, a sustainable approach for rehabilitating mercury (Hg)-contaminated soils, can be enhanced by arbuscular mycorrhizal (AM) fungi, which promote plant growth and metal uptake, including Hg, in contaminated soils. Hg, despite lacking a biological function in plants, can be absorbed and translocated using Zn and/or Cd transporters, as these elements belong to the same group in the periodic table (12/2B). In fact, the specific transporters of Hg in plant roots remain unknown. This study is therefore to provide fundamental insights into the prospect to remediate Hg-contaminated soils, with a focus on the role of AM fungi. The hypothesis posits that Hg uptake in plants may be facilitated by transporters responsible for Zn/Cd, affected by AM fungi. The Scopus database was used to collect studies between 2000 and 2022 with a focus on the ecological role of AM fungi in environments contaminated with Zn and Cd. Particular emphasis was laid on the molecular mechanisms involved in metal uptake and partitioning. The study revealed that AM fungi indeed regulated Zn and/or Cd transporters, influencing Zn and/or Cd uptake in plants. However, these effects vary significantly based on environmental factors, such as plant and AM fungi species and soil conditions (e.g., pH, phosphorus levels). Given the limited understanding of Hg remediation, insights gained from Zn and Cd transporter systems can guide future Hg research. In conclusion, this study underscores the importance of considering environmental factors and provides fundamental insights into the potential of Hg phytoremediation with the assistance of AM fungi.
Back to the roots: understanding banana below‐ground interactions is crucial for effective management of Fusarium wilt
(2022) Were, Evans; Viljoen, Altus; Rasche, Frank
Global banana production is affected by Fusarium wilt, a devastating disease caused by the soilborne root‐infecting fungus, Fusarium oxysporum f. sp. cubense (Foc). Fusarium wilt is notoriously difficult to manage because infection arises through complex below‐ground interactions between Foc, the plant, and the soil microbiome in the root–soil interface, defined as the rhizosphere. Interactions in the rhizosphere play a pivotal role in processes associated with pathogen development and plant health. Modulation of these processes through manipulation and management of the banana rhizosphere provides an auspicious prospect for management of Fusarium wilt. Yet, a fundamental understanding of interactions in the banana rhizosphere is still lacking. The objective of this review is to discuss the state‐of‐the‐art of the relatively scant data available on banana below‐ground interactions in relation to Fusarium wilt and, as a result, to highlight key research gaps. Specifically, we seek to understand (a) the biology of Foc and its interaction with banana; (b) the ecology of Foc, including the role of root‐exuded metabolites in rhizosphere interactions; and (c) soil management practices and how they modulate Fusarium wilt. A better understanding of molecular and ecological factors influencing banana below‐ground interactions has implications for the development of targeted interventions in the management of Fusarium wilt through manipulation of the banana rhizosphere.
Brewing a sustainable future: a firm-level analysis of sustainability initiatives in the coffee sector
(2025) Boller, Meta Leonie; Bosch, Christine; Heinzel, Kathleen; Birkenberg, Athena; Krupitzer, Christian
The coffee industry has long relied on third-party certification as their approach to sustainability, driven by customer demand and changing consumer behavior. Today, multiple forms of sustainability engagement have developed in the industry. This study uses a machine learning approach to analyze the engagement in sustainability initiatives of 100 firms active in the German market. Results reveal that company size and value chain position influence choice and engagement intensity in sustainability initiatives. A complementary literature analysis on policy recommendations to promote sustainability engagement in the coffee industry revealed a fragmented and insufficiently granular picture to address the diverse needs of stakeholders. While company characteristics significantly influence their choice of sustainability initiatives, policymakers often adopt generic approaches that do not reflect these nuances. Future research could extend this approach to deepen understanding or validate findings of policies for sustainable transformation in the coffee sector to other critical crops.
Coffee berry borer control, but not coffee yield, is mediated by non-additive interaction between birds and ants across different cultivation systems
(2026) Cardona Tejada, Damaris A.; Parra, Juan L.; Grass, Ingo; Schurr, Frank M.
Coffee is one of the most traded tropical crops, cultivated in some of the most biodiverse regions on the planet. Coffee production can be seriously reduced by the coffee berry borer (CBB), a specialized beetle that feeds on the endosperm of coffee berries. Given the CBB's economic relevance, coffee-producing countries have developed extensive Integrated Pest Management programs. Nonetheless, most of these programs fail to incorporate CBB control by natural enemies such as birds and ants. While the effects of birds and ants on CBB suppression have been demonstrated to be positive when studied in isolation, their interactive effects have been little studied. To better understand the effects of the trophic interaction between birds and ants on CBB control, we conducted a full-factorial block experiment excluding birds and ants from coffee shrubs. We distributed 49 experimental blocks across three different coffee systems in a Colombian landscape: sun-exposed coffee, coffee-plantain intercropping, and shade coffee. We found birds to be key control agents of CBB: in the presence of ants, bird exclusion increased CBB infestation by 36 %. However, in the absence of ants, birds had little effect on CBB infestation, demonstrating that the effects of birds and ants were non-additive. This suggests that birds control CBB through a trophic cascade mediated by ants. We also found that the effects of exclusions were modified by the cultivation system, with the shade coffee system consistently reducing CBB infestation. Our experiment demonstrates that crop diversification is an effective measure for integrating local enemies into IPM strategies. Nonetheless, we acknowledge that trophic interactions are highly complex and exhibit a context-dependency that can result in the suppression of biological pest control. Therefore, we recommend conducting future analysis on evaluating the effects of predator´s community composition to encourage the development of IPM programs that leverage biodiversity in agroecosystems.
Complementary ecosystem services from multiple land uses highlight the importance of tropical mosaic landscapes
(2023) Raveloaritiana, Estelle; Wurz, Annemarie; Osen, Kristina; Soazafy, Marie Rolande; Grass, Ingo; Martin, Dominic Andreas; Bemamy, Claudine; Ranarijaona, Hery Lisy Tiana; Borgerson, Cortni; Kreft, Holger; Hölscher, Dirk; Rakouth, Bakolimalala; Tscharntke, Teja
Tropical agricultural landscapes often consist of a mosaic of different land uses, yet little is known about the spectrum of ecosystem service bundles and materials they provide to rural households. We interviewed 320 households on the different benefits received from prevalent land-use types in north-eastern Madagascar (old-growth forests, forest fragments, vanilla agroforests, woody fallows, herbaceous fallows, and rice paddies) in terms of ecosystem services and plant uses. Old-growth forests and forest fragments were reported as important for regulating services (e.g. water regulation), whilst fallow lands and vanilla agroforests as important for provisioning services (food, medicine, fodder). Households reported the usage of 285 plant species (56% non-endemics) and collected plants from woody fallows for varying purposes, whilst plants from forest fragments, predominantly endemics, were used for construction and weaving. Multiple land-use types are thus complementary for providing ecosystem services, with fallow lands being particularly important. Hence, balancing societal needs and conservation goals should be based on diversified and comprehensive land management.
Complementary effects of pollination and biocontrol services enable ecological intensification in macadamia orchards
(2024) Anders, Mina; Westphal, Catrin; Linden, Valerie M. G.; Weier, Sina; Taylor, Peter J.; Grass, Ingo
In many crops, both pollination and biocontrol determine crop yield, whereby the relative importance of the two ecosystem services can be moderated by the landscape context. However, additive and interactive effects of pollination and biocontrol in different landscape contexts are still poorly understood. We examined both ecosystem services in South African macadamia orchards. Combining observations and experiments, we disentangled their relative additive and interactive effects on crop production with variation in orchard design and landscape context (i.e., cover of natural habitat and altitude). Insect pollination increased the nut set on average by 280% (initial nut set) and 525% (final nut set), while biocontrol provided by bats and birds reduced the insect damage on average by 40%. Pollination services increased in orchards where macadamia tree rows were positioned perpendicular to orchard edges facing natural habitat. Biocontrol services decreased with elevation. Pest damage was reduced by higher cover of natural habitat at landscape scale but increased with elevation. Pollination and biocontrol are both important ecosystem services and complementary in providing high macadamia crop yield. Smart orchard design and the retention of natural habitat can simultaneously enhance both services. Conjoint management of ecosystem services can thus enable the ecological intensification of agricultural production.
Determining the footprint of breeding in the seed microbiome of a perennial cereal
(2024) Michl, Kristina; David, Christophe; Dumont, Benjamin; Mårtensson, Linda-Maria Dimitrova; Rasche, Frank; Berg, Gabriele; Cernava, Tomislav
Background: Seed endophytes have a significant impact on plant health and fitness. They can be inherited and passed on to the next plant generation. However, the impact of breeding on their composition in seeds is less understood. Here, we studied the indigenous seed microbiome of a recently domesticated perennial grain crop (Intermediate wheatgrass, Thinopyrum intermedium L.) that promises great potential for harnessing microorganisms to enhance crop performance by a multiphasic approach, including amplicon and strain libraries, as well as molecular and physiological assays. Results: Intermediate wheatgrass seeds harvested from four field sites in Europe over three consecutive years were dominated by Proteobacteria (88%), followed by Firmicutes (10%). Pantoea was the most abundant genus and Pantoea agglomerans was identified as the only core taxon present in all samples. While bacterial diversity and species richness were similar across all accessions, the relative abundance varied especially in terms of low abundant and rare taxa. Seeds from four different breeding cycles (TLI C3, C5, C704, C801) showed significant differences in bacterial community composition and abundance. We found a decrease in the relative abundance of the functional genes nirK and nifH as well as a drop in bacterial diversity and richness. This was associated with a loss of amplicon sequence variants (ASVs) in Actinobacteria , Alphaproteobacteria , and Bacilli , which could be partially compensated in offspring seeds, which have been cultivated at a new site. Interestingly, only a subset assigned to potentially beneficial bacteria, e.g. Pantoea, Kosakonia , and Pseudomonas , was transmitted to the next plant generation or shared with offspring seeds. Conclusion: Overall, this study advances our understanding of the assembly and transmission of endophytic seed microorganisms in perennial intermediate wheatgrass and highlights the importance of considering the plant microbiome in future breeding programs.
Development of highly digestible fish feeds from locally available resources in Iran
(2025) Salehi, Hamed; Focken, Ulfert
In 2012, global aquaculture production (excluding aquatic plants) was 63.5 million tons, increasing to 94.4 million tons by 2022—a growth of 48%. In Iran, production rose by 62% during the same period, from 296,514 to 480,624 tons. Iran is a leading producer of rainbow trout (Oncorhynchus mykiss W.), contributing 15-21% of the global supply from 2012 to 2022. However, aquafeed, which accounts for 70% of production costs and 80% of environmental effluents, has been impacted by a decline in fish meal production in 2023. This may increase costs, especially for carnivorous species like rainbow trout, necessitating alternative protein sources. Currently, canola meal, a potential plant-based protein, is not widely used in Iran due to poor utilization by fish. Furthermore, local poultry by-products are viewed as low-quality protein sources compared to those in countries like Germany, due to a lack of processing technologies, which restricts their utilization in aquafeed industry. Therefore, some of these products like blood and feather meals are realised not comparable to fish meal in feeding rainbow trout for the aquafeed industry in Iran. Nutrient eutrophication in water bodies necessitates development of environmentally friendly aquafeed out of highly-digestible feed components, as well. Therefore, this research was conducted to assess the digestibility of various feed components, including poultry by-products such as PBM, BM, FeM, PPCon and plant-based proteins like CM and SBM, in rainbow trout. The test ingredients were incorporated into a semi-purified casein-based diet at a 30:70 ratio, with TiO₂ used as a marker, and then fed to the experimental fish. Feces were collected using the settling method in 57-liter aquaria. The apparent protein digestibility coefficients for PBM, FeM, PPCon, BM, CM, and SBM were 73%–93%, 73%–96%, 100%, 87%, 94%, and 97%, respectively. The most digestible feed components in terms of CP were chosen to create five fish-meal-free diets, with increasing levels of CM ranging from 20% to 40%, to compare with a casein-based diet in terms of growth performance and apparent digestibility in juvenile rainbow trout. Subsequently, the 35% CM diet, which achieved the least cost FCR, was slightly modified and extruded to feed fattening rainbow trout in tanks. This diet was then compared to a pelleted caseinbased diet to assess growth performance and nutrient effluents in tanks and simultaneously, the assessment of CP, CL,OMdigestibility as well as the availability of P in juvenile rainbow trout in aquaria set-up using the settling method. This extruded grow-out feed, which included 35% CM and approximately 32% highly digestible poultry by-products, proved to be comparable to the highly digestible semi-purified casein-based diet in terms of supporting growth performance and body criteria in rainbow trout. The utilization of macronutrients like CL, CP, and OM in this extruded feed was remarkably similar to that of the control feed (p>0.05). However, the P load from this practical diet was higher in the water compared to the control feed (p<0.05). This issue could potentially be addressed by lowering the phosphorus concentration in the feed for fish of that size and considering the phosphorus availability of each component used in the diet. This investigation showed that when terrestrial protein sources are properly combined to provide all essential nutrients to the fish, feeds without FM can not only promote high growth performance but also enable efficient nutrient utilization in rainbow trout. Lastly, properly processed poultry by-products can serve as valuable protein sources for the growing aquafeed industry in developing countries like Iran.
Diacetoxyscirpenol, a Fusarium exometabolite, prevents efficiently the incidence of the parasitic weed Striga hermonthica
(2022) Anteyi, Williams Oyifioda; Klaiber, Iris; Rasche, Frank
Background: Certain Fusarium exometabolites have been reported to inhibit seed germination of the cereal-parasitizing witchweed, Striga hermonthica , in vitro . However, it is unknown if these exometabolites will consistently prevent S. hermonthica incidence in planta . The study screened a selection of known, highly phytotoxic Fusarium exometabolites, in identifying the most potent/efficient candidate (i.e., having the greatest effect at minimal concentration) to completely hinder S. hermonthica seed germination in vitro and incidence in planta , without affecting the host crop development and yield. Results: In vitro germination assays of the tested Fusarium exometabolites (i.e., 1,4-naphthoquinone, equisetin, fusaric acid, hymeglusin, neosolaniol (Neo), T-2 toxin (T-2) and diacetoxyscirpenol (DAS)) as pre- Striga seed conditioning treatments at 1, 5, 10, 20, 50 and 100 µM, revealed that only DAS, out of all tested exometabolites, completely inhibited S. hermonthica seed germination at each concentration. It was followed by T-2 and Neo, as from 10 to 20 µM respectively. The remaining exometabolites reduced S. hermonthica seed germination as from 20 µM ( P < 0. 0001). In planta assessment (in a S. hermonthica -sorghum parasitic system) of the exometabolites at 20 µM showed that, although, none of the tested exometabolites affected sorghum aboveground dry biomass ( P > 0.05), only DAS completely prevented S. hermonthica incidence. Following a 14-d incubation of DAS in the planting soil substrate, bacterial 16S ribosomal RNA (rRNA) and fungal 18S rRNA gene copy numbers of the soil microbial community were enhanced; which coincided with complete degradation of DAS in the substrate. Metabolic footprinting revealed that the S. hermonthica mycoherbicidal agent, Fusarium oxysporum f. sp. strigae (isolates Foxy-2, FK3), did not produce DAS; a discovery that corresponded with underexpression of key genes (Tri5, Tri4) necessary for Fusarium trichothecene biosynthesis ( P < 0.0001). Conclusions: Among the tested Fusarium exometabolites, DAS exhibited the most promising herbicidal potential against S. hermonthica . Thus, it could serve as a new biocontrol agent for efficient S. hermonthica management. Further examination of DAS specific mode of action against the target weed S. hermonthica at low concentrations (≤ 20 µM), as opposed to non-target soil organisms, is required.
Enhancing weed suppression in plants by artificial stress induction
(2025) Merkle, Michael; Petschenka, Georg; Belz, Regina; Gerhards, Roland
Various plant species from the Poaceae, Cannabaceae, and Brassicaceae families are used as cover crops to suppress weeds and volunteer crops through competition and allelopathy. This study examined the effects of artificially induced stress on the physiological processes, total phenolic content (TPC), and allelopathic potential of the plant species Avena strigosa, Cannabis sativa , and Sinapis alba at an early growth stage with the aim to increase their weed suppression abilities. Stress was induced at the 3–4 leaf stage in greenhouse-grown plants via harrowing, methyl jasmonate (MeJA) application, insect stress simulation, or a combination of insect stress and harrowing. Maximum quantum yield of photosystem II and shoot dry matter in the three plant species were only minimally or not affected a few days after treatment (DAT). Insect stress caused visible symptoms on treated leaves in all plants. The TPC in the shoot extracts of combined stress-treated C. sativa and insect-stressed S. alba was significantly higher by 1.7 and 1.9 times, respectively, five DAT compared to the shoot extracts from untreated control plants. Additionally, laboratory bioassays with aqueous shoot extracts from the untreated and treated plants were conducted to identify changes in allelopathic potential within the shoot tissues. The application of shoot extracts from MeJA-treated C. sativa and S. alba resulted in the lowest seed germination rates for the two weed species Alopecurus myosuroides and Stellaria media , as well as for the volunteer wheat Triticum aestivum , which were up to 65% lower 10 DAT compared to seeds treated with shoot extracts from non-stressed plants. However, the root-suppressing effect of the shoot extracts on weeds was not influenced by the stress treatments. This study reveals that artificial stress induction can be a suitable management strategy to enhance weed and volunteer cereal suppression in plants in an early growth stage but may vary between stress types and plant species, and requires further optimization and field testing.
Evaluating the protein value of fresh tropical forage grasses and forage legumes using in vitro and chemical fractionation methods
(2021) Salazar-Cubillas, Khaterine C.; Dickhöfer, Uta
The objectives of the present study were (1) to assess the adequacy of the in vitro and chemical methods to predict post-ruminal crude protein supply (PRCP) from fresh tropical forage, and (2) to identify PRCP supply predictors. Twenty-three fresh forage grasses and 15 forage legumes commonly used in domestic cattle feeding in the tropics and subtropics were incubated in the rumen of cows to determine ruminal crude protein (CP) degradation. The PRCP supply was calculated from in situ rumen-undegraded CP and in vitro organic matter digestibility (i.e., reference method), from ammonia-nitrogen release during in vitro incubation (i.e., in vitro method), and from the concentrations of chemical CP fractions (i.e., chemical method). The adequacy was evaluated using error-index and dimensionless parameters, and stepwise regression was used to select PRCP predictors. Adequacy ranged from poor to moderate (0.53 to 0.74) for the in vitro method being lower for forage legumes at a slow rumen passage rate (0.20), and even poorer (0.02 to 0.13) for the chemical method. Hence, the in vitro method can estimate PRCP supply in tropical forages with moderate to high but not with slow passage rates. Equations developed in the present study appear to predict PRCP supply with reasonable adequacy.
Genetic and non‐genetic factors influencing KLH binding natural antibodies and specific antibody response to Newcastle disease in Kenyan chicken populations
(2022) Miyumo, Sophie; Wasike, Chrilukovian B.; Ilatsia, Evans D.; Bennewitz, Jörn; Chagunda, Mizeck G. G.
This study aimed at investigating the influence of genetic and non‐genetic factors on immune traits to inform on possibilities of genetic improvement of disease resistance traits in local chicken of Kenya. Immune traits such as natural and specific antibodies are considered suitable indicators of an individual's health status and consequently, used as indicator traits of disease resistance. In this study, natural antibodies binding to Keyhole Limpet Hemocyanin (KLH‐NAbs) was used to measure general disease resistance. Specific antibodies binding to Newcastle disease virus (NDV‐IgG) post vaccination was used to measure specific disease resistance. Titers of KLH‐NAbs isotypes (KLH‐IgM, KLH‐IgG and KLH‐IgA) and NDV‐IgG were measured in 1,540 chickens of different ages ranging from 12 to 56 weeks. A general linear model was fitted to determine the effect of sex, generation, population type, phylogenetic cluster, line, genotype and age on the antibody traits. A multivariate animal mixed model was fitted to estimate heritability and genetic correlations among the antibody traits. The model constituted of non‐genetic factors found to have a significant influence on the antibody traits as fixed effects, and animal and residual effects as random variables. Overall mean (±SE) concentration levels for KLH‐IgM, KLH‐IgG, KLH‐IgA and NDV‐IgG were 10.33 ± 0.04, 9.08 ± 0.02, 6.00 ± 0.02 and 10.12 ± 0.03, respectively. Sex, generation and age (linear covariate) significantly (p < 0.05) influenced variation across all the antibody traits. Genotype effects (p < 0.05) were present in all antibody traits, apart from KLH‐IgA. Interaction between generation and line was significant (p < 0.05) in KLH‐IgM and NDV‐IgG while nesting phylogenetic cluster within population significantly (p < 0.05) influenced all antibody traits, apart from KLH‐IgA. Heritability estimates for KLH‐IgM, KLH‐IgG, KLH‐IgA and NDV‐IgG were 0.28 ± 0.08, 0.14 ± 0.06, 0.07 ± 0.04 and 0.31 ± 0.06, respectively. There were positive genetic correlations (0.40–0.61) among the KLH‐NAbs while negative genetic correlations (−0.26 to −0.98) were observed between the KLH‐NAbs and NDV‐IgG. Results from this study indicate that non‐genetic effects due to biological and environmental factors influence natural and specific antibodies and should be accounted for to reduce bias and improve accuracy when evaluating the traits. Subsequently, the moderate heritability estimates in KLH‐IgM and NDV‐IgG suggest selection possibilities for genetic improvement of general and specific immunity, respectively, and consequently disease resistance. However, the negative correlations between KLH‐NAbs and NDV‐IgG indicate the need to consider a suitable approach that can optimally combine both traits in a multiple trait selection strategies.
Governance of land rehabilitation and remediation: case studies of Ghana’s small-scale mining sector
(2024) Adu-Baffour, Ferdinand Ababio; Birner, Regina
The artisanal and small-scale mining (ASM) sector is a complex and evolving industry that presents unique challenges within the global resource landscape. Despite its traditional labeling as artisanal, ASM operations are increasingly becoming mechanized, utilizing heavy machinery and hazardous chemicals such as mercury and cyanide for mineral extraction. Concurrently, the informal nature of most ASM operations limits effective top-down regulatory enforcements due to governance challenges. These developments have led to wide spreads of degraded, contaminated and abandoned rural community lands which also serve as valuable agricultural and forest lands for inhabitants of affected mining communities. While the existing literature has extensively analyzed the impacts of these developments on local, national, and global economies, ecologies, health, and welfare, there remains a notable gap in understanding the governance of rehabilitating and remediating affected environments post-mineral extraction. Furthermore, phytoremediation – a biological innovation which can help remediate contaminated sites and address the problem of soil degradation and erosion, with reported economic and environmental benefits – has only seen very limited global commercial adoption. In regions where traditional remediation approaches are financially untenable, like in the Global South, however, phytoremediation is argued to be a suitable and viable solution towards a greener future for remediation and environmental restoration. This thesis aims to address the knowledge gaps pertaining to the governance of rehabilitating and remediating affected environments affected by mineral extraction in the artisanal and small-scale mining (ASM) sector. Specifically, it focuses on systematically investigating the governance challenges in ASM, exploring community-based solutions for sustainable land restoration, and proposing a framework for the broader-based application of phytoremediation to address land contamination in the small-scale gold mining sector in Ghana. These research objectives are structured around three chapters, with the first two focusing on empirical case studies and the last chapter serving as a review of scientific and grey literature, as well as project reports on land rehabilitation and phytoremediation. Chapter 2, which addresses the first objective, delves into the obstacles hindering the implementation of the legal framework for artisanal small-scale mining (ASM) in Ghana. The first part conducts an institutional analysis of the legal and political framework governing Ghana’s small scale mining sector, with a particular focus on its implications for post-mined land rehabilitation efforts. This is followed by an assessment of the practical application of the legal framework in the context of small-scale gold mining (ASGM) value chain, using the Process Net-Mapping tool along with stakeholder interviews. The study reveals outdated legislation, formal licensing bureaucracies, land tenure issues, and ineffective collaboration among stakeholders as major bottlenecks. Drawing on these insights, the chapter discusses the broader implications of the findings for the effective running of the ASGM value chain and recommends, among other things, the adoption of collaborative governance systems, like co-management, to ensure sustainability. Chapter 3, which addresses the second objective, examines community-based solutions for sustainable mined land restoration through a case study of an NGO-initiated project in five active mining communities in Ghana's Amansie West district. The chapter utilizes a combination of qualitative methods including the participatory Net-Mapping tool to explore conditions under which local communities would engage in restoration efforts without financial incentives, revealing community support, using communal labor, dependent on factors like land tenure arrangements and local leadership influence. The study underscores the potential of community-led efforts for land rehabilitation, emphasizing the role of social networks, norms, and land tenure structures. Chapter 4, which addresses the third objective, introduces a conceptual framework for the effective and sustainable application of phytoremediation to clean contaminated lands resulting from mining activities. This is the result of insights drawn from existing phytoremediation literature, including case studies where the field application or/and commercialization of phytoremediation has been successful, and lessons gleaned from other real-world applications of the technology. The framework encompasses technical considerations across the phytoremediation process and identifies the socio-cultural, economic, political, and institutional conditions necessary for successful large-scale implementation. The paper provides valuable guidance for regions seeking to leverage phytoremediation to benefit society and the environment. In conclusion, this thesis contributes to understanding the challenges facing the ASM sector and proposes innovative solutions to address governance issues, promote community-based land restoration, and facilitate the scaling of phytoremediation initiatives for sustainable development in the mining sector, particularly in developing regions. The holistic approach advocated in this thesis underscores the importance of legal reforms tailored to the constantly evolving ASM sector, stakeholder collaboration, adaptive governance systems, and community engagement to effectively navigate the intricate ASM landscape and maximize its beneficial effects on local livelihoods and development worldwide.
Identifying governance challenges in scaling biofortification programs and the potential of training: a case study of Uganda
(2025) Alioma, Richard; Zeller, Manfred; Birner, Regina; Bosch, Christine; Muayahoto, Bho; Zeller, Manfred; Department of Rural Development Theory and Policy, Hohenheim University, Stuttgart, Germany; Birner, Regina; Department of Social and Institutional Change in Agricultural Development, Hohenheim University, Stuttgart, Germany; Bosch, Christine; Department of Social and Institutional Change in Agricultural Development, Hohenheim University, Stuttgart, Germany; Muayahoto, Bho; HarvestPlus, International Food Policy Research Institute, Washington, DC, United States
Introduction: Biofortification initiatives can significantly help reduce micronutrient deficiencies in developing countries. However, when hidden hunger affects a large segment of the population, large-scale implementation is necessary to achieve the desired results. We aimed to identify governance challenges in biofortification, and potential remedies based on a conceptual framework that considers low demand and the invisible nature of micronutrient traits in crops. Methods: Using process net maps and quantitative methods, this paper explores how farmer training can address governance issues. Results: Results show that, in addition to common agricultural marketing issues, sweet potato vine multipliers struggle with vine supply, value chain actors adulterate iron beans, and consumers are hesitant to pay higher prices for biofortified crops. These problems may result from information asymmetry, merit goods, collective action issues, and free riding. Furthermore, training had little impact on reducing the governance challenge arising from information asymmetry. Discussion/conclusion: One of the key solutions was investing in subsidies to increase production and raise awareness of the importance of nutritious foods. With governance problems, there is a need to take them into consideration when planning and expanding biofortification programs.
Market potential for organic dairy and meat products from “calf-friendly” dairy farms across different consumer segments
(2025) Herrler, Mareike; Chagunda, Mizeck G. G.; Stroebele-Benschop, Nanette
As public criticism of the management of surplus dairy calves increases, new approaches are required to improve calf welfare to maintain the dairy industry’s license to produce. Little is known about consumers’ willingness to buy (WTB) organic dairy and meat products from farms that aim to improve the welfare of surplus dairy calves. This study aims to address this research gap by identifying potential target groups for assessing the market potential of these products in south-west Germany. For this purpose, an online survey was conducted among 922 participants in this region. Participants were presented with one of three scenarios describing different rearing systems for dairy calves that hold the potential to provide enhanced calf welfare in comparison to current dairy farming practices: Cow-calf contact, the use of dual-purpose breeds and on-farm slaughter. Factor and cluster analyses were performed to identify potential target groups for organic dairy and meat products from these “calf-friendly” rearing systems. The four clusters Conscious organic shoppers, Moderate sustainability advocates, The indifferent consumers and the Interested organic refusers were identified. The findings indicate that organic consumers who care about calf welfare and prioritize product quality and sustainability when buying food are a promising target group for products from “calf-friendly” organic dairy farms. Consumers’ WTB seems to depend more on their general attitudes and financial means than on the presented scenarios. By identifying a potential target group for these products, this study fills a research gap and may contribute to more effective and targeted marketing.
Mungbean response to regulated deficit irrigation: a trade‐off between productivity and adaptability?
(2025) Pataczek, Lisa; Hakenberg, Tim; Hilger, Thomas; Nair, Ramakrishnan M.; Schafleitner, Roland; Asch, Folkard; Cadisch, Georg
Water scarcity, elevated temperatures, as well as pests and diseases have been demonstrated to have a detrimental effect on the yield potential of mungbean ( Vigna radiata ). The cultivation of improved mungbean genotypes with regulated deficit irrigation (RDI), a water‐saving irrigation strategy, has been identified as a promising approach to enhance yield stability of the crop and ensure food security. Thus, the purpose of this study was to identify adaptation strategies and possible trade‐offs to drought of mungbean genotypes under deficit irrigation and the effect on yield by investigating in particular assimilate re‐allocation. Four genotypes (NM11, AVMU 1604, AVMU 1635, KPS2) were cultivated in a greenhouse under three treatments of RDI with depletion fractions as a percentage of total available soil water (TAW) of 0.45, 0.65, and 0.8, corresponding to a recommended irrigation schedule, moderate and severe water deficit, respectively. Samples were collected at the flowering and maturity stages, and the dry matter, dry matter partitioning, yield, harvest index, pod harvest index, water use efficiency, and carbon‐13 isotope discrimination to estimate transpiration efficiency were determined. The study found that productivity (i.e., grain yield) was not lowered as a trade‐off of adaptability to water deficit irrigation. The genotypes either did not respond to deficit irrigation (KPS2 and AVMU 1635) in terms of grain yield or exhibited increased remobilisation of assimilates, either from pod walls to seeds (NM11) or from vegetative plant parts to pods/seeds (AVMU 1604), thereby increasing yields by 38% and 52%, respectively, under water deficit. However, the genotype KPS2 demonstrated stable yields and the greatest harvest index/pod harvest index (36%/69%) across all RDI treatments, suggesting superior adaptability to fluctuating water availability and efficient resource allocation, providing a suitable choice for a range of environmental conditions.
Rainforest fragmentation decreases the robustness of plant‐frugivore interaction networks
(2025) Becker, David; Li, Wande; Gurung, Ashtha; Rodriguez Martinez, Eduardo; Rojas, Emmanuel; Rodríguez‐Herrera, Bernal; Vollstädt, Maximilian G. R.; Grass, Ingo; Hiller, Thomas
Tropical rainforests are biodiversity hotspots that provide a variety of ecosystem functions and services. Seed dispersal by fruit‐eating birds is an important ecosystem process in the regeneration of tropical rainforests, which is increasingly threatened by widespread deforestation. In particular, the expansion of agricultural land often leads to forest fragmentation, which can have a negative impact on the interactions between plants and frugivores and thus on seed dispersal. However, little is known about how forest fragmentation affects the structure and robustness of plant–frugivore interaction networks. Here, we examined the effects of forest fragmentation on species richness of frugivorous birds interacting with focal tree species, and the structure and robustness of plant–frugivore interaction networks in the tropical lowland forests of northern Costa Rica. Species richness of frugivorous birds at the forest edges increased with fragment size and forest cover in the surrounding landscape as well as with local fruit availability. Modularity and robustness of plant–frugivore networks increased with enhanced fragment size and forest cover, while network specialization (H2′) increased only with greater forest cover. Additionally, the three common tanager species ( Ramphocelus passerinii , Thraupis palmarum , and Thraupis episcopus ) were identified as key bird species for network functioning by promoting among‐module and within‐module connectivity. Conservation measures should therefore not only focus on threatened specialist species, but more on the key species that enhance network structure and consequently increase the robustness of these trophic interaction networks. Ultimately, our study demonstrates that tropical forest fragmentation simplifies network structure, making these interactions more vulnerable to anthropogenic disturbances.
Reclaimed water driven lettuce cultivation in a hydroponic system: the need of micropollutant removal by advanced wastewater treatment
(2021) Kreuzig, Robert; Haller-Jans, Jaqueline; Bischoff, Cornelia; Leppin, Johannes; Germer, Jörn; Mohr, Marius; Bliedung, Alexa; Dockhorn, Thomas
For a novel approach of resource-efficient water reuse, a municipal wastewater treatment plant was extended at pilot scale for advanced wastewater treatment, i.e., ozonation and biological activated carbon filtration, and a hydroponic system for reclaimed water driven lettuce cultivation. The treatment specific wastewater lines with the corresponding lettuce plants, differentiated into roots and shoots, were monitored for priority wastewater micropollutants, i.e., acesulfame (sweetener), caffeine (stimulant), carbamazepine, diclofenac, ibuprofen, sulfamethoxazole with acetyl-sulfamethoxazole (human pharmaceuticals), 1H-benzotriazole, and 4/5-methylbenzotriazole (industrial chemicals). As clearly demonstrated, conventional tertiary treatment could not efficiently clean up wastewater. Removal efficiencies ranged from 3% for carbamazepine to 100% for ibuprofen. The resulting pollution of the hydroponic water lines led to the accumulation of acesulfame, carbamazepine, and diclofenac in lettuce root systems at 32.0, 69.5, and 135 μg kg−1 and in the uptake of acesulfame and carbamazepine into lettuce shoots at 23.4 and 120 μg kg−1 dry weight, respectively. In contrast, both advanced treatment technologies when operating under optimized conditions achieved removal efficiencies of > 90% also for persistent micropollutants. Minimizing the pollution of reclaimed water thus met one relevant need for hydroponic lettuce cultivation.

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