Publicação
Innovative strategies to mitigate effects of climate change for sustainable hazelnut production
| Resumo: | Climate change affects directly several economic sectors, namely agriculture, forestry, energy consumptions, tourism among others. In agriculture, the climate change has a huge impact on crop growth and yield. This takes great importance in perennial fruit crops due to their higher sensitivity to environmental conditions, particularly on floral differentiation, blossom, pollination, fruit setting and growth stages. Temperate fruit treesrequire some chilling during the development, however climate change is making climates warmer, which significantly influence the crops growth and yield. Furthermore, the average global temperature will move plant species to new areas with more favourable climate conditions. These difficulties will be transversal to all perennial fruit species being hazelnut (Corylus avellana L.) one of them, especially those growing in Mediterranean countries. The main objective of this Doctoral Thesis is to contribute with strategies to mitigate effects of climate change and on the other hand, to enhance the quality and production of hazelnut by different approaches. To achieve these goals, an evaluation of the suitability of preharvest foliar spray treatments was performed, gaining a further insight in the agricultural management strategies by understanding the plant physiological and biochemical response, enhance hazelnut quality, environmental sustainability and economic viability for hazelnut production. In addition, regarding the massive amounts of bio-wastes, namely the hazelnut husks, the determination of the suitability of husks (hazelnut by-product) as a source of bioactive compounds was also studied. In this sense, two experiments were carried out, the first experiment consisted in spraying treatments combined with irrigation: kaolin (K, 4%); natural bioestimulant Ascophyllum nodosum (An, 0.15%); salicylic acid (SA, 0.01 %); K with irrigation (Ki); An with irrigation (Ani); SA with irrigation (SAi); control with irrigation (Ci) and control (C), during 2016 and 2017, in a hazelnut orchard with adult trees in full production using an economically important hazelnut cultivar ‘Grada de Viseu’, located in Moimenta da Beira (Northern Portugal). A positive effect of the spray treatment on ‘Grada de Viseu’ yield, physiological and biochemical responses was shown. Results showed that K and An were effective for reducing hazelnut heat and drought stresses by increasing the relative water content, net CO2 assimilation rate, water use efficiency and by reducing the leaf mass per area and electrolyte leakage. Moreover, concentration of abscisic acid, malondialdehyde, proline, lipid peroxidation and the average content of antioxidant enzymes was lower, suggesting that under K and An treatments, plants have a better physiological performance than control trees. Under K, An and SA with and without irrigation treatments, the content of total sugars decreased and the content of starch, salicylic acid, thiols and the ratio between total chlorophylls and total carotenoids increased, demonstrating that these treatments can be effective against drought. These treatments affected positively the biometric parameters, namely nut and kernel sizes, vitamin E levels, antioxidant activity and some phenolic compound contents. The sensorial attributes were not affected by the treatments, this way the application of K, AN and SA improve the hazelnut tree physiological response to the climate change, without compromising the hazelnut chemical and sensorial quality. Other experiment was carried in a hazelnut orchard with adult trees in full production in Vila Real, Portugal. Hazelnuts husks were obtained from four cultivars: ‘Butler’, ‘Grada de Viseu’, ‘Morell’ and ‘Lansing’, and the bioactive potential of hazelnut husks was determined as a function of their cultivar source and extraction solvent. A total of 11 phenolics were identified. The results showed that cultivar and extraction solvent influenced significantly the extraction yield. Methanolic husk extracts exhibited the greatest antioxidant potentials followed by water and acetone. ‘Grada de Viseu’ husks presented the highest content of individual phenolics and antioxidant activity, while the husks from the cultivar ‘Lansing’ showed the lowest levels. The valorization of hazelnuts husks gives an important contribution for the isolation and purification of bioactive molecules. In conclusion, this thesis contributed to increase knowledge of the use of promising preharvest compounds for the improvement of the hazelnut physiological and biochemical performance as well the nut quality. Nonetheless lower and non-significant differences between treatments with and without irrigation were observed revealing that K, An and SA can be used without irrigation to mitigate summer stress effects being these compounds useful strategies to mitigate climate change effects for sustainable hazelnut production |
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| Autores principais: | Cabo, Sandra Cristina Santos do |
| Assunto: | Corylus avellana L. kaolin |
| Ano: | 2020 |
| País: | Portugal |
| Tipo de documento: | tese de doutoramento |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade de Trás-os-Montes e Alto Douro |
| Idioma: | inglês |
| Origem: | Repositório da UTAD |
| Resumo: | Climate change affects directly several economic sectors, namely agriculture, forestry, energy consumptions, tourism among others. In agriculture, the climate change has a huge impact on crop growth and yield. This takes great importance in perennial fruit crops due to their higher sensitivity to environmental conditions, particularly on floral differentiation, blossom, pollination, fruit setting and growth stages. Temperate fruit treesrequire some chilling during the development, however climate change is making climates warmer, which significantly influence the crops growth and yield. Furthermore, the average global temperature will move plant species to new areas with more favourable climate conditions. These difficulties will be transversal to all perennial fruit species being hazelnut (Corylus avellana L.) one of them, especially those growing in Mediterranean countries. The main objective of this Doctoral Thesis is to contribute with strategies to mitigate effects of climate change and on the other hand, to enhance the quality and production of hazelnut by different approaches. To achieve these goals, an evaluation of the suitability of preharvest foliar spray treatments was performed, gaining a further insight in the agricultural management strategies by understanding the plant physiological and biochemical response, enhance hazelnut quality, environmental sustainability and economic viability for hazelnut production. In addition, regarding the massive amounts of bio-wastes, namely the hazelnut husks, the determination of the suitability of husks (hazelnut by-product) as a source of bioactive compounds was also studied. In this sense, two experiments were carried out, the first experiment consisted in spraying treatments combined with irrigation: kaolin (K, 4%); natural bioestimulant Ascophyllum nodosum (An, 0.15%); salicylic acid (SA, 0.01 %); K with irrigation (Ki); An with irrigation (Ani); SA with irrigation (SAi); control with irrigation (Ci) and control (C), during 2016 and 2017, in a hazelnut orchard with adult trees in full production using an economically important hazelnut cultivar ‘Grada de Viseu’, located in Moimenta da Beira (Northern Portugal). A positive effect of the spray treatment on ‘Grada de Viseu’ yield, physiological and biochemical responses was shown. Results showed that K and An were effective for reducing hazelnut heat and drought stresses by increasing the relative water content, net CO2 assimilation rate, water use efficiency and by reducing the leaf mass per area and electrolyte leakage. Moreover, concentration of abscisic acid, malondialdehyde, proline, lipid peroxidation and the average content of antioxidant enzymes was lower, suggesting that under K and An treatments, plants have a better physiological performance than control trees. Under K, An and SA with and without irrigation treatments, the content of total sugars decreased and the content of starch, salicylic acid, thiols and the ratio between total chlorophylls and total carotenoids increased, demonstrating that these treatments can be effective against drought. These treatments affected positively the biometric parameters, namely nut and kernel sizes, vitamin E levels, antioxidant activity and some phenolic compound contents. The sensorial attributes were not affected by the treatments, this way the application of K, AN and SA improve the hazelnut tree physiological response to the climate change, without compromising the hazelnut chemical and sensorial quality. Other experiment was carried in a hazelnut orchard with adult trees in full production in Vila Real, Portugal. Hazelnuts husks were obtained from four cultivars: ‘Butler’, ‘Grada de Viseu’, ‘Morell’ and ‘Lansing’, and the bioactive potential of hazelnut husks was determined as a function of their cultivar source and extraction solvent. A total of 11 phenolics were identified. The results showed that cultivar and extraction solvent influenced significantly the extraction yield. Methanolic husk extracts exhibited the greatest antioxidant potentials followed by water and acetone. ‘Grada de Viseu’ husks presented the highest content of individual phenolics and antioxidant activity, while the husks from the cultivar ‘Lansing’ showed the lowest levels. The valorization of hazelnuts husks gives an important contribution for the isolation and purification of bioactive molecules. In conclusion, this thesis contributed to increase knowledge of the use of promising preharvest compounds for the improvement of the hazelnut physiological and biochemical performance as well the nut quality. Nonetheless lower and non-significant differences between treatments with and without irrigation were observed revealing that K, An and SA can be used without irrigation to mitigate summer stress effects being these compounds useful strategies to mitigate climate change effects for sustainable hazelnut production |
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