Environmental pollution of heavy metals has become an increasing problem. Environmental risk assessments can be conducted to investigate and determine the potential risk of polluted terrestrial environments. Traditionally, risk assessments are based on total soil metal concentrations on a dry weight basis. Assessments based on total concentrations do not account for metal bioavailability. The bioavailable fraction of the metal is that available for metabolic uptake over a biological membrane, and it is largely controlled by the physiochemical characteristics of the soil solution. For soil-dwelling organisms the most important physiochemical parameters governing copper toxicity are pH and dissolved organic carbon. To incorporate these parameters into risk assessments mechanistic chemical equilibrium models can be used, such as biotic ligand models. These have previously been applied to mainly aquatic environments and only in recent years they have been expanded to the terrestrial realm. The overall aim of this thesis was to test the applicability of a leachate-based biotic ligand model, which takes pH dependency into account, for ecotoxicological risk assessment of soil-dwelling organisms. Toxicity data with associated soil solution pH for seven soil-dwelling organisms and microbially mediated soil processes were obtained from the Swedish Geotechnical Institute. Physiochemical soil characteristics of three Swedish field sampled soils amended with biochar were also obtained from the Swedish Geotechnical Institute. The toxicity data were used to derive two key parameters for calibration of the soil biotic ligand model through linear regression analysis i.e., the pH dependency and the species-specific intrinsic sensitivity. The calibrated biotic ligand models were applied to the field soils and species sensitivity distributions were derived for each soil to calculate hazardous metal concentrations. A simplified risk assessment of the soils was performed based on the results of the leachate-based biotic ligand models and on measured total concentrations on a dry weight basis.  As expected, the results of the regression analysis showed a strong pH dependency between toxicity effect concentrations and pH. For all included test organisms, the copper toxicity effect concentration decreased as the pH of the soil solution increased. Although Cu2+ toxicity increased with increasing pH, the considered organisms showed individual and varying pH-dependencies especially at pH 3-4 and pH 7-8. Further, the results showed that the risk assessment based on the Swedish EPA method, which use total metal concentrations on a dry weight basis, yielded different results than risk assessment based on the leachate-based biotic ligand models. The soils that had been amended with biochar contained lower total Cu concentrations on a dry weight basis compared to those which had not been amended. Consequently, total Cu concentrations exceeded the guideline value for sensitive land-use only in the non-amended soils. Total Cu concentrations exceeded the guideline value for less sensitive land-use in all field soils. Similar to total Cu concentrations on a dry weight basis, the total dissolved Cu concentrations also decreased with added biochar. The same trend could not be seen for Cu2+ in CaCl2 leachates. DOC in the leachates decreased with added biochar, suggesting that biochar sorbs DOC. A majority of the total dissolved Cu was bound to DOC and only a small fraction left as free ions.  The lower DOC concentrations led to higher Cu2+ concentrations in the leachate. Consequently, two of the biochar amended soils had Cu2+ concentrations exceeding the calculated HC50 (protection level for LSL). The predicted toxic effect concentrations ranged from 0.001 μg/L for the most sensitive organism Tomato shoot (L. esculentum) to 3.53 μg/L for the least sensitive organism Soil induced respiration (SIR). The most sensitive field soil had the highest measured pH and had been amended with 6% biochar, the two least sensitive field soils had the lowest measured pH and had been amended with 3 and 6% biochar respectively. The risk assessment based on the soil-BLM approach yielded different, but not less conservative, results compared to the traditional risk assessment based on total concentrations on a dry weight basis. The expected result was for the BLM-based risk assessment to be less conservative as it takes the site-specific bioavailability into account. The leachate-based soil-BLM seems to be sensitive to changes and variations of the input parameters in the speciation. To improve the robustness of the model, and accuracy of risk assessments, additional organisms should be included in the SSDs and speciation should be performed on soils with a wider range of pH. The potential of leachate-based BLMs for risk assessment has been demonstrated. The results invite to further v development of leachate-based soil-BLMs and has the potential to increase the knowledge of the chemistry and toxicology of copper in soils as well as the effects and behaviour of biochar as a metal sorbent.

[ES] El pimiento (C. annuum) ocupa un importante lugar en la economía agrícola del mundo y en particular para España. La agricultura intensiva empleada en las últimas décadas está demostrando no ser sostenible a largo plazo, esto, y la aceleración del cambio climático, hace necesario la búsqueda de plantas más adaptadas a las nuevas presiones de estresores tanto bióticos como abióticos. Adicional al uso de variedades mejoradas para este tipo de estresores, es importante tomar en cuenta las interacciones que ocurren en el suelo e introducirlas en los programas de mejora genética vegetal. Por ello, esta tesis se ha centrado, por un lado, en la búsqueda de fuentes de resistencia frente a oídio (L. taurica), enfermedad que cada vez está resultando más problemática en pimiento, especialmente en agricultura ecológica. Por otro lado, y teniendo en cuenta la importancia de la sanidad y fertilidad del suelo para la resiliencia de los cultivos, se estudia la interacción del sistema radicular del pimiento con la zona de la rizosfera y la microbiota de la raíz. Como principales resultados obtenidos en la presente tesis se pueden destacar la identificación de fuentes de resistencia a oídio en las accesiones de C. annuum var. glabriusculum, lo que puede facilitar la introducción de genes de resistencia en variedades comerciales de pimientos. Además, se ha demostrado cómo las propiedades de la rizosfera (actividad enzimática, movilización de nitrógeno, respiración) y su microbioma es altamente dependiente de las condiciones de cultivo y del genotipo cultivado. Así se observó que la parcela de cultivo ecológico mostró mayores recuentos microbianos, actividades enzimáticas y movilización de nitrógeno que la convencional además de poseer más diversidad microbiana y mayor recuento de microorganismos. Por último, se observó también una gran especificidad de la interacción suelo-planta, observándose cómo ciertos microorganismos beneficiosos colonizaban preferentemente ciertos genotipos. Esta especificidad debería de ser considerada para futuros programas de mejoramiento para una agricultura más sostenible y adaptada. / [CA] El pebrot (C. annuum) ocupa un lloc important en l'economia agrícola del món i en particular per a Espanya. L'agricultura intensiva emprada en les últimes dècades està demostrant no ser sostenible a llarg termini, açò, i l'acceleració del canvi climàtic, fa necessari la recerca de plantes més adaptades a les noves pressions d'estressors tant biòtics com a abiòtics. Addicional a l'ús de varietats millorades per a este tipus d'estressors, és important tindre en compte les interaccions que ocorren en el sòl i introduir-les en els programes de millora genètica vegetal. Per açò, aquesta tesi s'ha centrat, d'una banda, en la recerca de fonts de resistència front a oídi (L. taurica), malaltia que cada vegada està resultant més problemàtica en pebrot, especialment en agricultura ecològica. D'altra banda, i tenint en compte la importància de la salut i fertilitat del sòl per a la resiliència dels cultius, s'estudia la interacció del sistema radicular del pebrot amb la zona de la rizosfera i la microbiota de l'arrel. Com a principals resultats obtinguts en la present tesi es poden destacar la identificació de fonts de resistència a oídi en les accessions de C. annuum var. glabriusculum, la qual cosa pot facilitar la introducció de gens de resistència en varietats comercials de pebrots. A més, s'ha demostrat com les propietats de la rizosfera (activitat enzimàtica, mobilització de nitrogen, respiració) i el seu microbioma és altament dependent de les condicions de cultiu i del genotip cultivat. Així es va observar que la parcel·la de cultiu ecològic va mostrar majors recomptes microbians, activitats enzimàtiques i mobilització de nitrogen que la convencional, a més de posseir més diversitat microbiana i major recompte de microorganismes. Finalment, es va observar també una gran especificitat de la interacció sòl-planta, observant-se com certs microorganismes beneficiosos colonitzaven preferentment certs genotips. Aquesta especificitat hauria de ser considerada per a futurs programes de millorament per a una agricultura més sostenible i adaptada. / [EN] The pepper (C. annuum) holds an important place in the global agricultural economy and particularly for Spain. Intensive agriculture used in recent decades is proving not to be sustainable in the long term, and, coupled with the acceleration of climate change, it necessitates the search for plants more adapted to new pressures from both biotic and abiotic stressors. In addition to using improved varieties for these types of stressors, it is important to consider the interactions that occur in the soil and incorporate them into plant genetic improvement programs. Therefore, this thesis has focused on one hand, on the search for sources of resistance against powdery mildew (L. taurica), a disease that is increasingly problematic in pepper, especially in organic agriculture. On the other hand, considering the importance of soil health and fertility for crop resilience, the interaction of the pepper root system with the rhizosphere zone and root microbiota is studied. The main results obtained in this thesis include the identification of sources of resistance to powdery mildew in the accessions of C. annuum var. glabriusculum, which can facilitate the introduction of resistance genes in commercial pepper varieties. Furthermore, it has been shown how the properties of the rhizosphere (enzymatic activity, nitrogen mobilization, respiration) and its microbiome are highly dependent on the cultivation conditions and the cultivated genotype. It was observed that the organic farming plot showed higher microbial counts, enzymatic activities, and nitrogen mobilization than the conventional one, in addition to possessing greater microbial diversity and higher counts of microorganisms. Lastly, a high specificity of the soil-plant interaction was also observed, with certain beneficial microorganisms preferentially colonizing specific genotypes. This specificity should be considered for future breeding programs for more sustainable and adapted agriculture. / El presente trabajo no podría haberse llevado a cabo sin el apoyo financiero de la beca predoctoral otorgada por CONACYT-CONCYTEP con el número identificador 47274 por parte del gobierno de México. / Morales Manzo, II. (2023). Mejora genética del chile (Capsicum annuum L.) para estrés biótico: Oídio (Leveillula taurica (Lév.) Arn.) y fertilidad del suelo: retos de la agricultura ecológica y búsqueda de fuentes de variación de interés y factores genéticos relacionados [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/194538

At present, soils face great threats. Consequences of human activities, such as climate change, acidification and contamination result in decreased soil health. This is a threat to human health and well-being, since our society is dependent on soil ecosystem services. The soil ecosystems provide resources, such as food and fresh water, regulate the climate and play key parts in important life supporting biological processes, e.g. cycling of carbon and nutrients. Due to increased awareness of the threats that soils face, and its importance to humans, soil quality monitoring has recently received increased attention. Microorganisms run most biological processes in the soil, such as decomposition of organic material and nutrient cycling. Thus, microbial activity and diversity are considered useful biological indicators for soil quality monitoring. These biological properties can be examined using different methods. The aim of the project was to evaluate the potential of multiple substrate-induced respiration (MSIR), using the MicroRespTM system, and isothermal calorimetry for determining microbial activity and diversity in soils contaminated with copper (Cu) and polycyclic aromatic hydrocarbons (PAH). Thereby, the methods’ applicability in risk assessment of contaminated soil could be decided. MSIR is considered appropriate for determining microbial activity and functional diversity, while isothermal calorimetry has not been tested as much in this area. The calorespirometric ratio (produced heat per unit CO2) was calculated to evaluate potential relationships between heat and CO2 at different contamination levels. Although there was some variation between the methods, Cu had a clear effect on both microbial activity and functional diversity. Both methods were thus considered applicable in risk assessment of soil contaminated with Cu. The impact of PAH appeared to be more complex, the effects on microbial activity varied and PAH had little significant effect on functional diversity. Neither of the methods were therefore considered applicable for assessment of soil contaminated with PAH. The calorespirometric ratio did not provide useful results, and cannot be recommended for risk assessment purposes at present. / I dagsläget utsätts marken för stora hot. Följder av mänsklig aktivitet, så som klimatförändringar, försurning och förorening försämrar markens kvalitet. Detta är ett hot mot människors hälsa och välmående, eftersom vårt samhälle är beroende av markens ekosystemtjänster. Markens ekosystem förser oss med exempelvis mat och rent vatten, reglerar klimatet, och har nyckelroller i viktiga biologiska processer, exempelvis cirkulering av kol och näringsämnen. På grund av ökad medvetenhet om hoten mot marken samt dess betydelse för människan, har kontroll av markens kvalitet börjat få ökad uppmärksamhet. Mikroorganismer sköter de flesta biologiska processer som sker i marken, så som nedbrytning av organiskt material och cirkulering av näringsämnen. Därmed anses mikrobiell aktivitet och diversitet vara lämpliga biologiska indikatorer vid kontroll av markens kvalitet. Dessa biologiska egenskaper kan mätas med flera olika metoder. Syftet med projektet var att utvärdera potentialen i att använda multipla substrat-inducerad respiration (MSIR), genom att använda systemet MicroRespTM, samt isotermisk kalorimetri för att mäta mikrobiell aktivitet och funktionell diversitet i mark förorenad med koppar (Cu) och polycykliska aromatiska kolväten (PAH). Därmed kunde metodernas tillämplighet i riskbedömning av förorenad mark bestämmas. MSIR anses vara en lämplig metod i syfte att undersöka mikrobiell aktivitet och funktionell diversitet, medan isotermisk kalorimetri inte är lika beprövat. Kvoten mellan värmeproduktion och respirerad CO2, the calorespirometric ratio, beräknades för att utvärdera eventuella samband mellan värmeproduktion och respiration vid olika föroreningskoncentrationer. Trots att det förekom viss variation mellan metoderna, hade Cu en tydlig effekt på både mikrobiell aktivitet och funktionell diversitet. Båda metoder ansågs därför vara tillämpbara i riskbedömning av Cu-förorenad jord. PAH hade varierande effekt på mikrobiell aktivitet och liten signifikant effekt på funktionell diversitet. Ingen av metoderna ansågs därför tillämpbar i riskbedömning av jord förorenad med PAH. The calorespirometric ratio tillhandahöll ej användbara resultat, och kunde därmed inte rekommenderas i riskbedömningssyfte.

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