Efectos a largo plazo del riego deficitario en la producción del almendro

Introduction. The recent favourable market perspectives for almonds around the world have induced important changes in Spanish almond production systems during the last 10 years. Earlier, the production was dominated by traditional rainfed orchards in marginal areas with small trees and average yields below 300 kg ha-1. Such systems have given way in some areas to an intensification of the crop with the important appearance of new irrigated plantations. These plantations have increased their area by more than 300% since 2014, and follow the Californian production standards where irrigation together with intensive mineral fertilization and phytosanitary management aim at yield objectives above 2000 kg ha-1. However, the lower availability of irrigation water in Spain makes the use of deficit irrigation strategies a widely adopted practice. Furthermore, the risks of severe restrictions of water availability for agriculture caused by the recurring droughts, common in the Mediterranean basin, poses an unknown challenge with potentially devastating effects for these new almond plantations. Research content. In 2014, López-López et al. (2018b) conducted research on almond irrigation in which they established four irrigation treatments (three deficit and one fully irrigated) to obtain the water production functions for irrigation, transpiration and evapotranspiration. In the present work, the experiment begun by López-López et al. (2018b) was continued for three more years in order to extend the period of study of the relationship between production and evapotranspiration and thus be able to generate a six-year production function. In addition, this extension allowed the study of the productive response during this second triennium and compare it with the response obtained during the first triennia and thus be able to identify adaptation or exhaustion phenomena of the trees as a result of the continued application of deficit irrigation strategies that could have altered the yield response. Additionally, another experiment was performed to study the effects associated with a single-season water deprivation to simulate a situation of severe water scarcity for agriculture caused by a persistent drought period. The effects on physiology and yield were measured during the season where the irrigation deficit was applied and in the subsequent seasons where irrigation was recovered to meet the ETC needs. Conclusions. The present work has generated an almond water production function obtained during six years. This water production function demonstrates that the evapotranspiration of an intensive adult almond plantation in southern Spain, yielding over 2.5 t ha-1, can exceed 1200 mm on the average, which corresponds to an irrigation depth of about 800-900 mm under the climatic conditions of Southwestern Spain. Under average productions greater than 2500 kg ha-1; deficit irrigation reduces kernel yields at a rate of 0.05 kg m-3 for irrigation levels close to the maximum and up to 0.35 kg m-3 for severe deficit irrigation (around 220 mm). These results are obtained when water stress is concentrated during the kernel-filling period, the least sensitive phenological stage of almond production to water stress. Furthermore, the data obtained suggest the non-significant appearance of adaptation or exhaustion phenomena due to the prolonged water deficits, which suggests the sustainability of the deficit irrigation strategies, at least for a six-year period under the experimental conditions. Remarkably, our experimental results simulating a single year drought, emphasised the vulnerability of irrigated almond orchards to a single-season severe irrigation deprivation. Despite the almond reputation as a drought-tolerant species, a total irrigation cut-off caused tree mortality greater than 90%. In the severe DI treatment (25% of full irrigation), negative effects on yield persisted in the two subsequent seasons, despite resuming full irrigation to restore the ETC demand in the following seasons.Introducción. Las recientes buenas perspectivas económicas del mercado de la almendra a nivel mundial han inducido importantes cambios en el cultivo del almendro en España durante los últimos 10 años. Un cultivo tradicionalmente dominado por las plantaciones en secano, relegadas a zonas marginales, árboles de escaso desarrollo y producciones medias inferiores a los 300 kg ha-1 de pepitas. Sin embargo, este sistema ha empezado a dar paso a una intensificación del cultivo con la aparición de nuevas plantaciones en regadío. Estas plantaciones han aumentado su superficie en más de un 300% desde 2014 y son plantaciones jóvenes que siguen los cánones productivos californianos donde el riego junto a un manejo intensivo de la fertilización y fitosanitario hacen que los objetivos productivos estén por encima de 2000 kg ha-1. No obstante, la baja disponibilidad hídrica de España provoca que el uso de estrategias de riego deficitario sean una actividad ampliamente adoptada. Además, el riesgo de restricciones severas de la disponibilidad hídrica para agricultura causadas por las recurrentes sequías persistentes en la Cuenca Mediterránea suponen un desafío desconocido con efectos potencialmente devastadores para estas nuevas plantaciones de almendro. Contenido de la investigación. En 2014, López-López et al.(2018b) comenzó un estudio en el cual estableció cuatro tratamientos de riego (tres deficitarios y uno totalmente regado) con el fin de obtener las funciones de producción para riego, transpiración y evapotranspiración. El presente trabajo continúa el trabajo de López-López et al.(2018b) durante tres años más con el objetivo de extender el periodo de estudio de las relaciones productiva y así poder construir una función de producción en respuesta al agua de seis años. Esta ampliación del estudio permitió además el estudio de la respuesta productiva durante este segundo trienio y la comparación con la respuesta obtenida durante el primer trienio con la finalidad de identificar fenómenos de adaptación o agotamiento de los árboles, fruto de la continuada aplicación de estrategias de riego deficitario y que hubieran podido alterar la respuesta productiva. También se realizó un experimento donde se aplicó durante una temporada un recorte severo de las dotaciones de riego simulando una situación de escasez de agua de riego por una sequía con el fin de estudiar los efectos tanto en la fisiología como en la producción de dos niveles severos de recorte de riego. Posteriormente se recuperaron los tratamientos de riego para cubrir la totalidad de las necesidades hídricas y se continuó monitoreando los árboles en busca de efectos arrastrados derivados del estrés aplicado. Conclusiones. El presente trabajo ha servido para determinar las funciones de producción en respuesta al agua en el cultivo del almendro durante un periodo de 6 años. Los datos obtenidos han demostrado que las necesidades hídricas de una plantación intensiva adulta de almendro en el sur de España pueden superar evapotranspiraciones (ETc) superiores a 1200 mm, lo que corresponde a necesidades de riego en torno 800-900 mm en las condiciones del suroeste español. Para producciones medias superiores a los 2500 kg ha-1; el riego deficitario reduce las producciones a un ritmo de 0.05 kg m-3 cuando los valores de riego están próximos a los máximos y estas reducciones alcanzan los 0.35 kg m-3 para valores de riego deficitario severo (en torno a 220 mm). Estos resultados se han obtenido concentrado el estrés hídrico durante el periodo de llenado de grano, la cual es reconocida como la fase fenológica con menor sensibilidad en términos de producción al estrés. Además, los datos obtenidos sugieren la no aparición significativa de fenómenos de adaptación o agotamiento por la acumulación del estrés hídrico, lo que sugiere la sostenibilidad de las estrategias de riego deficitario, al menos para un periodo de seis años bajo las condiciones experimentales aplicadas. Es especialmente destacable la vulnerabilidad de las plantaciones de almendro en regadío a un recorte severo del riego que ha mostrado este trabajo. A pesar de la reputación de esta especie como tolerante a la sequía un recorte total del riego puede provocar una mortalidad de árboles superior al 90%. Finalmente, los efectos negativos del estrés hídrico sobre la producción pueden persistir durante las siguientes temporadas si el estrés ha sido lo suficientemente severo, incluso habiéndose restablecido el riego para cubrir la totalidad de las necesidades hídricas de los árboles

Mechanosensitive regulation of stanniocalcin-1 by zyxin and actin-myosin in human mesenchymal stromal cells

Stanniocalcin-1 (STC1) secreted by mesenchymal stromal cells (MSCs) has anti-inflammatory functions, reduces apoptosis, and aids in angiogenesis, both in vitro and in vivo. However, little is known about the molecular mechanisms of its regulation. Here, we show that STC1 secretion is increased only under specific cell-stress conditions. We find that this is due to a change in actin stress fibers and actin-myosin tension. Abolishment of stress fibers by blebbistatin and knockdown of the focal adhesion protein zyxin leads to an increase in STC1 secretion. To also study this connection in 3D, where few focal adhesions and actin stress fibers are present, STC1 expression was analyzed in 3D alginate hydrogels and 3D electrospun scaffolds. Indeed, STC1 secretion was increased in these low cellular tension 3D environments. Together, our data show that STC1 does not directly respond to cell stress, but that it is regulated through mechanotransduction. This research takes a step forward in the fundamental understanding of STC1 regulation and can have implications for cell-based regenerative medicine, where cell survival, anti-inflammatory factors and angiogenesis are critical

Water Stress Enhances the Progression of Branch Dieback and Almond Decline under Field Conditions

Branch dieback and tree decline have been described as a common complex disease worldwide in woody crops, with Botryosphaeriaceae and Diaporthaceae being considered the most frequent fungi associated with the disease symptoms. Their behaviour is still uncertain, since they are considered endophytes becoming pathogenic in weakened hosts when stress conditions, such as water deficiency occur. Therefore, the main goal of this study was to determine if water stress enhances general decline on weakened almond trees subjected to different irrigation treatments under natural field conditions. In parallel, the occurrence of fungal species associated with almond decline was also determined in relation to disease progression by fungal isolation, and morphological and molecular based-methods. The symptoms of branch dieback and general decline were observed over time, mainly in the experimental plots subjected to high water deficiency. Botryosphaeriaceae were the most consistently isolated fungi, and Botryosphaeria dothidea was the most frequent. Collophorina hispanica was the second most frequent species and Diaporthe and Cytospora species were isolated in a low frequency. Most of them were recovered from both asymptomatic and symptomatic trees, with their consistency of isolation increasing with the disease severity. This work reveals the need to elucidate the role of biotic and abiotic factors which increase the rate of infection of fungal trunk pathogens, in order to generate important knowledge on their life cycle

Almond responses to a single season of severe irrigation water restrictions

A substantial area of the new almond plantations in Spain is under irrigation, but due to recurring severe droughts, the irrigation water allocation for agriculture can be drastically reduced eventually. This study assesses the physiological and yields effects of a single-season water deprivation (2017) over three seasons (2017–2019) on a previously well-irrigated mature almond [Prunus dulcis (Mill) D.A. Web, cv. Guara] orchard in southern Spain. Three irrigation treatments were imposed during 2017: full irrigation, applying the amount required to match maximum crop evapotranspiration (FI); sustained deficit irrigation applying 25% of FI (DI); and rain-fed which received no irrigation at all (RF). During 2018 and 2019, all treatments were irrigated as FI. The results document the vulnerability of irrigated almond orchards to severe water stress, as the rainfed treatment resulted in 92% tree mortality. In relation to FI, yield and quality were reduced in RF and DI by the negative impact of water stress on kernel weight and the formation of hull tights in the season of water deprivation. In the two following years, the negative impact on yields persisted due to reductions in fruit load (carry-over effects) even though trees in DI and RF were restored to full-irrigation levels. The three-year average yields of DI and RF treatments were less than what could be predicted from an almond production function obtained in the same orchard. This highlights the long-term negative impacts that severe water stress resulting from suspending or reducing drastically irrigation in a single season has on almond trees.This research was partially funded by the Spanish Ministry of Science, Innovation and Universities (MICINN), project AGL2015-66141-R, co-financed by the European Union FEDER Funds and project INNOVA-Clima (PR.AVA.AVA2019.051) funded by the European Regional Development Fund (FEDER). D.M. is a holder of a pre-doctoral fellowship funded by MICINN. ÁL-B was supported by a postdoctoral fellowship of the ‘Juan de la Cierva-Formación’ program (FJCI-2015-24109, Spanish Ministry of Economy and Competitiveness)

Mechanosensitive regulation of stanniocalcin-1 by zyxin and actin-myosin in human mesenchymal stromal cells

Stanniocalcin-1 (STC1) secreted by mesenchymal stromal cells (MSCs) has anti-inflammatory functions, reduces apoptosis, and aids in angiogenesis, both in vitro and in vivo. However, little is known about the molecular mechanisms of its regulation. Here, we show that STC1 secretion is increased only under specific cell-stress conditions. We find that this is due to a change in actin stress fibers and actin-myosin tension. Abolishment of stress fibers by blebbistatin and knockdown of the focal adhesion protein zyxin leads to an increase in STC1 secretion. To also study this connection in 3D, where few focal adhesions and actin stress fibers are present, STC1 expression was analyzed in 3D alginate hydrogels and 3D electrospun scaffolds. Indeed, STC1 secretion was increased in these low cellular tension 3D environments. Together, our data show that STC1 does not directly respond to cell stress, but that it is regulated through mechanotransduction. This research takes a step forward in the fundamental understanding of STC1 regulation and can have implications for cell-based regenerative medicine, where cell survival, anti-inflammatory factors and angiogenesis are critical

Correction to: Long-term almond yield response to deficit irrigation

A substantial area of the new almond plantations in Spain is under irrigation but because of water scarcity, deficit irrigation (DI) strategies have to be adopted. This study assesses the long-term sustainability of different DI strategies over 6 years (2014–2019) on a mature almond [Prunus dulcis (Mill) D.A. Web] orchard in southern Spain. Four irrigation treatments were imposed: full irrigation (FI); two moderate DI, (SDIM) and (RDIM), where applied irrigation was 65% of FI but differed in the seasonal water distribution; and a severe DI, where applied irrigation was 35% of FI. The results emphasise the key role of soil water storage and the importance to consider crop evapotranspiration (ETC) as the principal driving variable of productivity instead of irrigation in many situations. Soil water partially buffered the irrigation reductions imposed, leading to no significant differences in yield performance between the two different moderate DI treatments. The water production functions (yield versus applied irrigation and yield versus ETC) did not show statistical differences when comparing the first (2014–2016) against that of the second triennia (2017–2019), suggesting the non-existence of exhaustion or adaptation phenomena that could jeopardize the longer term sustainability of DI strategies. Average annual ETC ranged from 580 mm in the RDIS treatment to a maximum value of 1300 mm, yielding between 1370 and 2750 kg ha−1 of nuts, and showed that water deficits caused yield losses ranging from 0.05 to 0.35 kg m−3 of irrigation water depending on the irrigation level.This research was partially funded by the Spanish Ministry of Science, Innovation and Universities (MICINN), project AGL2015-66141-R, co-financed by the European Union FEDER Funds, project INNOVA-Clima (PR.AVA.AVA2019.051) funded by the European Regional Development Fund (FEDER) and project PCI2019-103621 by the MICINN. D.M. is a holder of a pre-doctoral fellowship funded by MICINN. ÁL-B was supported by a postdoctoral fellowship of the ‘Juan de la Cierva-Formación’ program (FJCI-2015-24109, Spanish Ministry of Economy and Competitiveness).Peer reviewe

Long-term almond yield response to deficit irrigation

A substantial area of the new almond plantations in Spain is under irrigation but because of water scarcity, deficit irrigation (DI) strategies have to be adopted. This study assesses the long-term sustainability of different DI strategies over 6 years (2014–2019) on a mature almond [Prunus dulcis (Mill) D.A. Web] orchard in southern Spain. Four irrigation treatments were imposed: full irrigation (FI); two moderate DI, (SDIM) and (RDIM), where applied irrigation was 65% of FI but differed in the seasonal water distribution; and a severe DI, where applied irrigation was 35% of FI. The results emphasise the key role of soil water storage and the importance to consider crop evapotranspiration (ETC) as the principal driving variable of productivity instead of irrigation in many situations. Soil water partially buffered the irrigation reductions imposed, leading to no significant differences in yield performance between the two different moderate DI treatments. The water production functions (yield versus applied irrigation and yield versus ETC) did not show statistical differences when comparing the first (2014–2016) against that of the second triennia (2017–2019), suggesting the non-existence of exhaustion or adaptation phenomena that could jeopardize the longer term sustainability of DI strategies. Average annual ETC ranged from 580 mm in the RDIS treatment to a maximum value of 1300 mm, yielding between 1370 and 2750 kg ha−1 of nuts, and showed that water deficits caused yield losses ranging from 0.05 to 0.35 kg m−3 of irrigation water depending on the irrigation level.This research was partially funded by the Spanish Ministry of Science, Innovation and Universities (MICINN), project AGL2015-66141-R, co-financed by the European Union FEDER Funds, project INNOVA-Clima (PR.AVA.AVA2019.051) funded by the European Regional Development Fund (FEDER) and project PCI2019-103621 by the MICINN. D.M. is a holder of a pre-doctoral fellowship funded by MICINN. ÁL-B was supported by a postdoctoral fellowship of the ‘Juan de la Cierva-Formación’ program (FJCI-2015-24109, Spanish Ministry of Economy and Competitiveness).Peer reviewe