Beyond conventional crops: exploring the potential of the alternative crops buckwheat and sorghum to cope with the future climate change conditions
- Autores: Xabier Simón Martínez de Goñi
- Directores de la Tesis: Usue Perez Lopez (dir. tes.), Ana Isabel Caño Delgado (dir. tes.)
- Lectura: En la Universidad del País Vasco - Euskal Herriko Unibertsitatea ( España ) en 2024
- Idioma: español
- Tribunal Calificador de la Tesis: Fermín Morales Iribas (presid.), Amaia Mena Petite (secret.), Omar Vergara Díaz (voc.), Beatriz Fernández Marín (voc.), Juan Arellano Martínez (voc.)
- Programa de doctorado: Programa de Doctorado en Agrobiología Ambiental por la Universidad del País Vasco/Euskal Herriko Unibertsitatea y la Universidad Pública de Navarra
- Materias:
- Enlaces
- Tesis en acceso abierto en: ADDI
- Resumen
- español
Environmental [CO2] has been rising exponentially over the last century, and projections indicate that this trend will continue through the end of the 21st century. In fact, it is expected that environmental [CO2] will rise from the current 400 ppm [CO2] to 700 ppm [CO2] by the end of the century. As a consequence, global temperatures are predicted to increase by 3 °C, causing drought episodes to increase not only in frequency, but also in intensity. Hence, climate change is one of the major threats to future agriculture and food demand, as future crops will face drought episodes in a high temperature and high [CO2] environment. Drought and high temperature are among the most damaging abiotic stresses for conventional crops such as wheat (Triticum aestivum) and maize (Zea mays). Currently, wheat and maize have great relevance, as they represent more than half of daily calorie intake derived from all cereal sources. Nevertheless, the global reliance on a limited number of conventional crops has put food security at risk, given that future climate change is projected to diminish their growth and yield. Considering that the human population is anticipated to reach 10.4 billion inhabitants by the end of the century, it is essential to identify alternative crops capable of withstanding future abiotic stresses to safeguard future food supply.In this PhD, we have worked with spelt (Triticum spelta) and buckwheat (Fagopyrum esculentum) two underutilized C3 crops as alternative crops for wheat. Likewise, sorghum (Sorghum bicolor), a C4 species primarily cultivated in Africa, was explored as an alternative crop for maize. The main hypotheses were that: 1) Alternative C3 crops spelt and buckwheat will be capable of withstanding drought better than the conventional C3 crop wheat, due to the ancestral genes of spelt and enhanced stomatal regulation and water use efficiency of buckwheat; 2) Modern varieties of the alternative C4 crop sorghum will exhibit superior growth compared to landrace sorghum varieties, but landraces are expected to show enhanced tolerance to water stress; and 3) Given that alternative crops are expected to exhibit greater drought resistance than conventional crops, they are expected to have a higher stress-threshold, and consequently will benefit more from the higher availability of environmental [CO2].In the Chapter 1 of this PhD thesis, we analysed the response of wheat and spelt to mild drought (one week at 40 % field capacity) and the response of buckwheat to extreme drought (one week at 20 % field capacity) in a greenhouse setup. We found mild drought to extremely damage photosynthetic machinery and processes in spelt, as well as increasing the dehydration in this species. Mild drought also caused decreases in photosynthesis in wheat, although to a lesser extent compared to spelt. On the contrary, upon exposure to extreme drought, buckwheat exhibited enhanced stomatal regulation, higher water-use efficiency, adequate water content within the plant and higher growth than wheat and spelt. Hence, the results of Chapter 1 indicate that buckwheat has the potential to be an alternative crop to wheat, while spelt does not.Chapter 2 delves deeper into the responses of wheat and buckwheat. In fact, we grewthese species in a growth chamber under ambient (400 ppm [CO2] and 24/18 °C day/night) and future (700 ppm [CO2] and 27/21 °C day/night) environmental conditions, with and without drought (one week at 20 % field capacity). In wheat, while high [CO2] and high temperature caused dehydration to increase, future drought extremely decreased photosynthesis, the quantum yield of PSII and increased antioxidant metabolism. In contrast, buckwheat exhibited optimal hydration levels, higher photosynthetic rates and increased water-use efficiency under the future conditions, regardless of the drought. This was explained by the enhanced stomatal regulation in buckwheat, and resulted in an outperforming growth compared to wheat. Therefore, the results of Chapter 2 underscore the promising potential of buckwheat as a suitable alternative crop to wheat for the future climatic scenarios.In Chapter 3 the focus shifts towards the response of maize and sorghum to the abiotic stresses of the future: we grew maize and sorghum under ambient (400 ppm [CO2] and 24/18 °C day/night) and future (700 ppm [CO2] and 27/21 °C day/night) environmental conditions, with and without drought (one week at 20 % field capacity). Under high [CO2] and high temperature, sorghum showed an enhanced stomatal regulation and water-use efficiency, which allowed it to consistently allocate resources towards growth. However, despite also exhibiting increased water-use efficiency, maize allocated resources towards maintenance. As a consequence, only the growth of sorghum was promoted. Under future drought, photosynthetic processes and machinery were extremely affected in maize, causing growth to be inhibited. In contrast, the improved stomatal regulation and increased root growth of sorghum led to a more moderate impact on photosynthesis and growth. Thus, the results of Chapter 3 highlight the potential of sorghum as an alternative crop to maize for the future.Lastly, Chapter 4 focuses on characterising the response of modern and landrace sorghum varieties under water-stress, evaluating their performance in both field and glasshouse conditions. We also included a maize variety as a conventional crop reference. In the field, water stress had little effect on the agronomic and photosynthetic traits. Conversely, in the glasshouse, landrace varieties exhibited greater height and a higher proportion of productive tillers. In the same manner, landrace varieties had an improved capacity to preserve water and a higher tolerance to water stress when their root system was not constrained by space. As species, sorghum produced more biomass than maize regardless of the environment and the water treatment. Hence, the results of Chapter 4 indicate that 1) although landraces showed greater tolerance to water stress for certain traits, specific modern varieties also showed high tolerance, 2) sorghum has superior growth under water stress compared to maize and 3) the experiments conducted under controlled environments may not be reproducible in real-field scenarios.Overall, the findings of this PhD thesis suggest that the alternative crops buckwheat and sorghum have the potential be alternatives for wheat and maize in the future, as they are capable of withstanding the abiotic stresses of the future. // Environmental [CO2] has been rising exponentially over the last century, and projections indicate that this trend will continue through the end of the 21st century. In fact, it is expected that environmental [CO2] will rise from the current 400 ppm [CO2] to 700 ppm [CO2] by the end of the century. As a consequence, global temperatures are predicted to increase by 3 °C, causing drought episodes to increase not only in frequency, but also in intensity. Hence, climate change is one of the major threats to future agriculture and food demand, as future crops will face drought episodes in a high temperature and high [CO2] environment. Drought and high temperature are among the most damaging abiotic stresses for conventional crops such as wheat (Triticum aestivum) and maize (Zea mays). Currently, wheat and maize have great relevance, as they represent more than half of daily calorie intake derived from all cereal sources. Nevertheless, the global reliance on a limited number of conventional crops has put food security at risk, given that future climate change is projected to diminish their growth and yield. Considering that the human population is anticipated to reach 10.4 billion inhabitants by the end of the century, it is essential to identify alternative crops capable of withstanding future abiotic stresses to safeguard future food supply.In this PhD, we have worked with spelt (Triticum spelta) and buckwheat (Fagopyrum esculentum) two underutilized C3 crops as alternative crops for wheat. Likewise, sorghum (Sorghum bicolor), a C4 species primarily cultivated in Africa, was explored as an alternative crop for maize. The main hypotheses were that: 1) Alternative C3 crops spelt and buckwheat will be capable of withstanding drought better than the conventional C3 crop wheat, due to the ancestral genes of spelt and enhanced stomatal regulation and water use efficiency of buckwheat; 2) Modern varieties of the alternative C4 crop sorghum will exhibit superior growth compared to landrace sorghum varieties, but landraces are expected to show enhanced tolerance to water stress; and 3) Given that alternative crops are expected to exhibit greater drought resistance than conventional crops, they are expected to have a higher stress-threshold, and consequently will benefit more from the higher availability of environmental [CO2].In the Chapter 1 of this PhD thesis, we analysed the response of wheat and spelt to mild drought (one week at 40 % field capacity) and the response of buckwheat to extreme drought (one week at 20 % field capacity) in a greenhouse setup. We found mild drought to extremely damage photosynthetic machinery and processes in spelt, as well as increasing the dehydration in this species. Mild drought also caused decreases in photosynthesis in wheat, although to a lesser extent compared to spelt. On the contrary, upon exposure to extreme drought, buckwheat exhibited enhanced stomatal regulation, higher water-use efficiency, adequate water content within the plant and higher growth than wheat and spelt. Hence, the results of Chapter 1 indicate that buckwheat has the potential to be an alternative crop to wheat, while spelt does not.Chapter 2 delves deeper into the responses of wheat and buckwheat. In fact, we grewthese species in a growth chamber under ambient (400 ppm [CO2] and 24/18 °C day/night) and future (700 ppm [CO2] and 27/21 °C day/night) environmental conditions, with and without drought (one week at 20 % field capacity). In wheat, while high [CO2] and high temperature caused dehydration to increase, future drought extremely decreased photosynthesis, the quantum yield of PSII and increased antioxidant metabolism. In contrast, buckwheat exhibited optimal hydration levels, higher photosynthetic rates and increased water-use efficiency under the future conditions, regardless of the drought. This was explained by the enhanced stomatal regulation in buckwheat, and resulted in an outperforming growth compared to wheat. Therefore, the results of Chapter 2 underscore the promising potential of buckwheat as a suitable alternative crop to wheat for the future climatic scenarios.In Chapter 3 the focus shifts towards the response of maize and sorghum to the abiotic stresses of the future: we grew maize and sorghum under ambient (400 ppm [CO2] and 24/18 °C day/night) and future (700 ppm [CO2] and 27/21 °C day/night) environmental conditions, with and without drought (one week at 20 % field capacity). Under high [CO2] and high temperature, sorghum showed an enhanced stomatal regulation and water-use efficiency, which allowed it to consistently allocate resources towards growth. However, despite also exhibiting increased water-use efficiency, maize allocated resources towards maintenance. As a consequence, only the growth of sorghum was promoted. Under future drought, photosynthetic processes and machinery were extremely affected in maize, causing growth to be inhibited. In contrast, the improved stomatal regulation and increased root growth of sorghum led to a more moderate impact on photosynthesis and growth. Thus, the results of Chapter 3 highlight the potential of sorghum as an alternative crop to maize for the future.Lastly, Chapter 4 focuses on characterising the response of modern and landrace sorghum varieties under water-stress, evaluating their performance in both field and glasshouse conditions. We also included a maize variety as a conventional crop reference. In the field, water stress had little effect on the agronomic and photosynthetic traits. Conversely, in the glasshouse, landrace varieties exhibited greater height and a higher proportion of productive tillers. In the same manner, landrace varieties had an improved capacity to preserve water and a higher tolerance to water stress when their root system was not constrained by space. As species, sorghum produced more biomass than maize regardless of the environment and the water treatment. Hence, the results of Chapter 4 indicate that 1) although landraces showed greater tolerance to water stress for certain traits, specific modern varieties also showed high tolerance, 2) sorghum has superior growth under water stress compared to maize and 3) the experiments conducted under controlled environments may not be reproducible in real-field scenarios.Overall, the findings of this PhD thesis suggest that the alternative crops buckwheat and sorghum have the potential be alternatives for wheat and maize in the future, as they are capable of withstanding the abiotic stresses of the future.
- euskara
[EU]Ingurumeneko [CO2] etengabe hazi da azken hamarkadetan, eta mende amaierarako espero da heltzea egungo 400 ppm [CO2]-tik 700 ppm [CO2]-ra. Horren ondorioz, aurreikusten da munduko tenperaturak 3 °C igotzeaz gain, gora egingo dutela lehorte-gertaeren kopuruak eta larritasunak. Beraz, etorkizunean labore konbentzionalek lehorteak jasango dituzte tenperatura altua eta [CO2] altua dituen ingurune batean. Gaur egun, garrantzi handia dute garia (Triticum aestivum) eta artoa (Zea mays) labore konbentzionalek, izan ere, eguneko zereal-iturrietatik jaten diren kalorien erdia baino gehiago dira. Dena dela, elikadura-segurtasuna arriskuan jarri du labore konbentzionalen kopuru txiki batekiko dugun elikadura-mendekotasun horrek, aurreikusten baita etorkizuneko klima-aldaketak horien hazkundea eta errendimendua txikituko dituela. Aintzakotzat hartuta giza populazioa 10.400 milioi biztanlera iritsiko dela mende bukaerarako, elikadura-hornidura ziurtatzeko ezinbestekoa da aurkitzea etorkizuneko estres abiotikoei aurre egiteko gai diren labore alternatiboak.
- español
