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Four new modes of action, oxathiapiprolin, fluopicolide, mandipropamid, and ethaboxam, have or are pending registrations on multiple tree crops in the USA including avocado, citrus, almond (and other tree nuts), and stone fruits to be used in sustainable anti-resistance rotation and mixture programs for managing Phytophthora diseases. All four fungicides are highly toxic in vitro against species of Phytophthora from different tree crops. Efficacy of foliar applications of oxathiapiprolin and mandipropamid for the management of citrus brown rot persisted for over 10 weeks. Still, residues could be removed to non-detectable levels by postharvest washing and brushing of fresh-market fruit. The four fungicides were highly effective in reducing root rot and crown/trunk cankers on tree crops and demonstrated acropetal systemic movement through the xylem after soil application and absorption by almond, citrus, and cherry roots. This was substantiated by reduced lesion size in stem inoculations of potted trees that were treated by soil applications or by in vitro bioassays and HPLC–MS–MS analyses of root, stem, and leaf extracts. Using an adapted Bromilow model that is based on the partition coefficient logP that indicates the lipo- or hydrophilicity and the acid dissociation constant pKa, mobility of ethaboxam, fluopicolide, mandipropamid, and oxathiapiprolin in plants was predicted, and this was supported by our studies. Mandipropamid and a mandipropamid–oxathiapiprolin pre-mixture are now registered as foliar applications for managing citrus brown rot, whereas oxathiapiprolin and fluopicolide are registered, and ethaboxam is pending registration as soil applications to control citrus root rot. Oxathiapiprolin has also been registered for soil use on almond and other nut crops, as well as avocado, and soil applications of mandipropamid are planned to be restricted to nursery use of multiple crops. [ABSTRACT FROM AUTHOR]

Recent economic, environmental, and regulative concerns force farmers to precise their fertilization practices. Yet, a critical knowledge gap concerning the temporal variability in perennials' nutritional requirements renders most fertilization applications inefficient. While mass balance studies could illustrate the dynamics of crops' mineral uptake, their association to field conditions remains a challenge. Hence, we constructed an empirical framework to convert data from lysimeter studies to applicable farming information. We fitted quadratic equations to the correlations between irrigation and drainage mineral concentrations of three perennial crops—almond, avocado, and pomegranate. Then, we derived the optimal irrigation mineral composition by the interpolation point of the nitrogen, phosphorus, and potassium curves. We also matched polynomials to the relations between leaf mineral concentrations and fertilization compositions and established mineral diagnostic references for each sampling period. Repeated measures of the crops' response curves illustrated a temporal variability in their nutrient uptake, highlighting that the evergreen avocado extracts nutrients throughout winter, early blooming almond extracts nutrients in spring, and late fruiting pomegranates obtain minerals throughout summer. Moreover, the deciduous almond and pomegranate require extensive summer fertilization for the following spring's bloom. Recurrent leaf diagnosis exhibited that almond leave's optimal nitrogen concentrations drop by midsummer. Optimal phosphorus concentrations in avocado and pomegranates doubled during summer, as did the optimal potassium concentration in pomegranates' leaves. Accordingly, we established an empirical approach to process data from lysimeter studies and constructed specific fertigation assays for almond, avocado, and pomegranate trees. [ABSTRACT FROM AUTHOR]

The differential stomatal regulation of transpiration among plant species in response to water deficit is not fully understood, although several hydraulic traits have been reported to influence it. This knowledge gap is partly due to a lack of direct and concomitant experimental data on transpiration, stomatal conductance, and hydraulic traits. We measured sap flux density (J s), stomatal conductance (g s), and different hydraulic traits in five crop species. Our aim was to contribute to establishing the causal relationship between water consumption and its regulation using a hydraulic trait-based approach. The results showed that the species-specific regulation of J s by g s was overall coordinated with the functional hydraulic traits analysed. Particularly relevant was the negative and significant relationship found between the Huber value (H v) and its functional analogue ratio between maximum J s and g s (J smax/ g smax) which can be understood as a compensation to maintain the hydraulic supply to the leaves. The H v was also significantly related to the slope of the relationship between g s and J s response to vapour pressure deficit and explained most of its variability, adding up to evidence recognizing H v as a major trait in plant water relations. Thus, a hydraulic basis for regulation of tree water use should be considered. [ABSTRACT FROM AUTHOR]

Temperate perennial fruit and nut trees play varying roles in world food diversity—providing edible oils and micronutrient, energy, and protein dense foods. In addition, perennials reuse significant amounts of biomass each year providing a unique resilience. But they also have a unique sensitivity to seasonal temperatures, requiring a period of dormancy for successful growing season production. This paper takes a global view of five temperate tree fruit crops—apples, cherries, almonds, olives, and grapes—and assesses the effects of future temperature changes on thermal suitability. It uses climate data from five earth system models for two CMIP6 climate scenarios and temperature‐related indices of stress to indicate potential future areas where crops cannot be grown and highlight potential new suitable regions. The loss of currently suitable areas and new additions in new locations varies by scenario. In the southern hemisphere (SH), end‐century (2081–2100) suitable areas under the SSP 5–8.5 scenario decline by more than 40% compared to a recent historical period (1991–2010). In the northern hemisphere (NH) suitability increases by 20% to almost 60%. With SSP1‐2.6, however, the changes are much smaller with SH area declining by about 25% and NH increasing by about 10%. The results suggest substantial restructuring of global production for these crops. Essentially, climate change shifts temperature‐suitable locations toward higher latitudes. In the SH, most of the historically suitable areas were already at the southern end of the landmass limiting opportunities for adaptation. If breeding efforts can bring chilling requirements for the major cultivars closer to that currently seen in some cultivars, suitable areas at the end of the century are greater, but higher summer temperatures offset the extent. The high value of fruit crops provides adaptation opportunities such as cultivar selection, canopy cooling using sprinklers, shade netting, and precision irrigation. [ABSTRACT FROM AUTHOR]

Olive agro-ecosystems in southern Italy have been heavily damaged due to Xylella fastidiosa subsp. pauca (Xfp). Replacing the Xfp-infected olive-growing areas with economically viable fruit tree species is thought to be a practical control measure. A land suitability analysis can provide an appropriate evaluation of a crop's suitability in these areas. We evaluate the suitability of almond (Prunus dulcis B.), fig (Ficus carica L.), hazelnut (Corylus avellana L.), kiwifruit (Actinidia chinensis P.), pistachio (Pistacia vera L.), and pomegranate (Punica granatum L.) as fruit tree species immune/resistant to Xfp to be planted within the Xfp-infected olive-growing areas in the Apulia region to compensate for economic and environmental losses. Climate and soil data were used to carry out the land suitability analysis. We combined information for each parameter to obtain the overall suitability maps for the six proposed fruit tree crops using GIS (Geographic Information System). The analysis showed that the Xfp-infected olive-growing areas are suitable for the plantation of most of the proposed fruit tree crops, with different suitability levels as the climate and soil conditions vary among the study areas. In particular, large olive-growing areas are suitable for the cultivation of pomegranate (268,886 ha), fig (103,975 ha), and almond (70,537 ha), followed by kiwifruit (43,018 ha) and pistachio (40,583 ha). Hazelnut, with just 2744 ha of suitable land, was the species with fewer suitable areas in these semi-arid environments. This is the first study to provide practical containment measures against the diffusion of Xfp in southern Italy. Our results can help in the selection of the right immune/resistant tree species for replanting in Xfp-infected zones, therefore providing guidelines within the decision-making process to encourage the planting of some underrepresented fruit tree crops with viable economic values as well. [ABSTRACT FROM AUTHOR]

The sustainability of woody crop agroecosystems requires continued improvements to water, nutrient and soil management. In this work, the combination of resource availability or fertigation dose with soil management practices was tested in a 2 × 2 factorial design in a drip irrigated young almond orchard. The fertigation doses were: the farmer supply at 60% of crop evapotranspiration and full nutrient requirements and the half-farmer supply at 30% of crop evapotranspiration and half nutrient requirements. The soil management practices were: bare soil and cover crops in the inter-row (mixture of grasses and legumes). Tree growth, yield, water and nutrient status, and cover crop biomass and nutrient status were determined, as well as inter-row soil C and N concentration. Results showed that the effect of resource availability was independent of soil management and vice versa. The half farmer treatment reduced tree vegetative growth and yield compared to farmer treatment, due to a negative effect on the water status, without observing a decrease in the concentration of nutrients in leaves or fruit. Trees with cover crop also reduced growth and yield compared to bare soil management. This was due to a nutritional competition, mainly of Ca, Fe, Mn and Zn, rather than to a decline in tree water status. Cover crops sequester up to 1 t/ha/year of carbon but do not increase soil organic carbon, nor soil total nitrogen. Cover crops proved to be efficient in reducing soil nitrate concentration in the topsoil and therefore has potential to prevent its leaching. Deficit fertigation and the use of cover crops can be effective practices to preserve and save water and nutrient resources in Mediterranean agroecosystems, but should be established with caution so as not to compromise the profitability of the orchard. [ABSTRACT FROM AUTHOR]

Almond (Amygdalus communis), is the most produced tree nut crop globally, with total production exceeding 1.3 million metric tons (INC 2020; RIJAL et al., 2021). Being a globally expanding crop lately, due to climate change caused by global warming, but also due to the growing demand for almond kernels (global demand has increased by 220%) - which leads to a potentially high profit, farmers' interest in this walnut, has also taken shape in Romania. In the world, the annual yield losses, in the case of almond orchards, due to the attack of diseases and pests can reach 20-30%. Studies on the taxonomy and diversity of harmful insects in almond orchards obviously have a large number of pests often found in Romania and around the world. Methods of direct observations and colored adhesive traps are used to collect specimens. Insects in the present study were collected from April to September 2021, with a decadal frequency, from an almond orchards located in Lovrin Development Research Station (Timiș, Romania). A number of 324 insect were collected and classified in two different orders (Hemiptera and Lepidoptera). The most abundant were the species belonging to the Aphididae family. Also, a high abundance presented the Diaspididae family. [ABSTRACT FROM AUTHOR]

BACKGROUND Water scarcity is a worldwide problem that leads to environmental and economic issues. Agriculture is one of the main consumers of water for irrigation and fertilization and almond is the major tree nut crop in the Mediterranean area. Furthermore, there is a continuous growing demand for healthy, vegan and sustainable products. Consequently, the present study aimed to chemically characterize almond milk powder enriched with probiotics manufactured from hydroSOStainable almonds (i.e. generated under water stress conditions). Almond milk powder enriched with probiotic bacteria was produced with almonds grown under optimal irrigation conditions (100% of the crop evapotranspiration) and was chemically compared to the samples made from hydroSOStainable almonds. Antioxidant activity, total phenolic content (TPC), minerals, organic acids and sugars, fatty acids, and descriptive sensory analysis were evaluated. RESULTS: The results showed that almond milk powder produced from hydroSOStainable almonds had a higher content of TPC, polyunsaturated fatty acids (PUFAs), PUFAs/saturated fatty acids (SFAs) ratio and PUFAs/monounsaturated fatty acids ratio, as well as almond and nutty flavors. Moderate and sustained deficit irrigation leads to powders with a higher content of PUFAs and PUFAs/SFAs ratio, which are parameters of utmost importance for health. CONCLUSION: Using these strategies, between 66% and 76% of the irrigation water can be saved, producing hydroSOStainable almond milk powder higher in TPC and PUFAs, as well as positive sensory attributes, compared to that from fully irrigated almonds. These findings may have a positive impact in both agriculture and food industry, allowing water savings and high quality and sustainable food products to be obtained. © 2020 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Tree nuts are globally consumed. Their kernels are calorie‐rich, nutrient‐dense foods and contain several bioactive and health‐promoting components. While some nut crops have expanded through the world since ancient times (almond, hazelnut, walnut), more recently, there has been a parallel development of underexploited promising species (Brazil nut, macadamia, pecan). Nut kernels have high lipid content, ranging from 40% to 80% depending on nut species and varieties. In general, nut oils contain significant proportions of nutritionally and medicinally desirable fatty acids and nutraceutical compounds (sterols, tocopherols, and other phenolics). A considerable genetic variability in oil content and composition is present in nut genetic resources worldwide. This suggests the possibility of different breeding lines focused to enhance oil yields, chemical and quality traits. Regarding extraction, screw‐pressing is suitable to achieve high oil recovery and good quality standards, but seed materials should be conditioned appropriately. Seed moisture content and pressing temperature appear as key variables to enhance oil recovery. This article presents an overview on chemical profiles, mechanical extraction, and quality concerns of oils from the most widely produced tree nut crops. The revision is also aimed at identifying areas where knowledge is insufficient and to set priorities for further research. Practical applications: The review updates and increases knowledge about oils from tree nut genetic resources, encompassing genetic variability and environmental effects on oil yield and compositional traits. It also analyzes findings regarding oil extraction and provides useful insights to establish better conditions for achieving sustainable oil yields and good quality standards. [ABSTRACT FROM AUTHOR]

Soil water or plant water status-based precision irrigation has the potential to improve water productivity. In this study, the question of number as well as placement of proximal sensors called leaf monitors that provide plant water status information has been addressed, to assist in implementation of precision irrigation. To accomplish this task, an algorithm based on the Fuzzy C-Means logic that utilized spatial variability in soil and plant attributes was developed. First, stable soil properties such as soil texture, digital elevation and apparent soil electrical conductivity data were used to create management zones (MZ). Following the creation of MZ, stem water potential data from an almond orchard and a vineyard located in California were used to determine number as well as the placement location of sensors within each MZ. The methodology and algorithm developed successfully indicated the number of sensors that need to be used and the location of the trees where the sensors should be installed. [ABSTRACT FROM AUTHOR]

Infection by the fungus Verticillium dahliae (Vd) and the bacterium Xylella fastidiosa (Xf) threatens the production of olives (Olea europaea L.) and almonds (Prunus dulcis Mill.) worldwide. Producing symptoms that resemble water stress or nutrient deficiency, infection by these vascular pathogens restricts water and nutrient flow through the xylem. Hyperspectral, narrow-band multispectral, and thermal imagery acquired at a high spatial resolution can detect disease symptoms, even before they are visible, potentially allowing growers to distinguish infected plants from those affected by confounding environmental stresses. Nevertheless, operational detection of vascular disease using high-resolution commercial satellite multispectral images remains to be evaluated. Here, we assessed the capacity of high-resolution Worldview-2 and -3 multispectral imagery to detect Xf and Vd infections in olive and almond orchards in Spain, Italy, and Australia between 2011 and 2021. We compared the accuracy of detecting both pathogens using the satellite imagery with results obtained using aerial high-resolution hyperspectral and thermal imaging, with model-inverted plant traits, solar-induced chlorophyll fluorescence (SIF), and thermal data as a reference. Our results using spectral plant traits to examine disease progression at all stages showed that traits and their importance varied as a function of disease severity. Worldview-2 and -3 detected the disease incidence with overall accuracies ranging from 0.63 to 0.83 and kappa coefficients (κ) ranging from 0.29 to 0.68. Nevertheless, detecting the early stages of disease with multispectral satellite data yielded poorer results, with κ values of 0.22–0.45, compared with κ values of 0.3–0.69 obtained from hyperspectral data. Typical multispectral bandsets available from satellite sensors cannot measure important plant traits such as the blue index NPQI, xanthophyll proxy PRI n , SIF, and anthocyanin levels, thus explaining the poorer results obtained from multispectral satellite data for the early detection of vascular diseases. Adding a thermal-based crop water stress indicator to the satellite data improved the overall accuracies by 10–15% and increased κ by >0.2 units. This work shows that commercial multispectral high-spatial resolution imagery can be used to detect intermediate and advanced Xf and Vd infection, but that the early detection of disease symptoms requires hyperspectral and thermal data. • Detection of symptoms due to vascular pathogens was evaluated with satellite imagery. • Hyperspectral and thermal images used as benchmark to assess the detection performance. • Both spectral bandsets were accurate to detect intermediate and advanced stages of infection. • Multispectral satellite data were unable to detect early stages of infection accurately. • Combining airborne thermal with satellite data improved accuracy up to 15% & κ ≥ 0.2. [ABSTRACT FROM AUTHOR]

California's Central Valley faces serious challenges of water scarcity and degraded groundwater quality due to nitrogen leaching. Orchard age is one of the key determinants for fruit and nut production and directly affects consumptive water use and fertilizer demand. However, regional and statewide spatially explicit information on orchard planting years in California is still lacking, despite some attempts to estimate tree ages using multi-temporal satellite imagery in other regions. Here we developed a robust detection method to track crop cover dynamics and identify the planting year through time series of Landsat imagery within the Google Earth Engine (GEE) platform. We used the full archive of Landsat data (Landsat-5 TM, Landsat-7 ETM+, and Landsat-8 OLI) from 1984 to 2017 as inputs and automated the GEE workflow for the on-fly-mapping. Preprocessing was initially performed using JavaScript to obtain high quality reflectance and Normalized Difference Vegetation Index (NDVI) time series for each Landsat pixel. Annual maximum NDVI was then aggregated to the orchard level based on the field boundary. Our change detection algorithm incorporated a set of decision rules, including adaptive identification of potential years with robust Z-score thresholds, elimination of false detections based on the post-planting growth curve, and estimation of planting year using the most recent minimum strategy. Our method showed a very high accuracy of estimating tree crop ages, with a R2 of 0.96 and a mean absolute error of less than half a year, when compared with 142 records provided by almond growers. We further evaluated the accuracy of the statewide mapping of planting years for all fruit and nut trees in California, and found an overall agreement of 89.2%. This automatic cloud-based application is expected to greatly strengthen our ability to forecast yield dynamics, estimate water use and fertilizer inputs, at individual field, county and statewide basis. [ABSTRACT FROM AUTHOR]

To identify predominant isolates for potential use as biocontrol agents, Aspergillus flavus isolates collected from soils of almond, pistachio and fig orchard in the Central Valley of California were tested for their membership to 16 atoxigenic vegetative compatibility groups (VCGs), including YV36, the VCG to which AF36, an atoxigenic isolate commercialized in the United States as biopesticide, belongs. A surprisingly large proportion of isolates belonged to YV36 (13.3%, 7.2% and 6.6% of the total almond, pistachio and fig populations, respectively), while the percentage of isolates belonging to the other 15 VCGs ranged from 0% to 2.3%. In order to gain a better insight into the structure and diversity of atoxigenic A . flavus populations and to further identify predominant isolates, seventeen SSR markers were then used to genetically characterize AF36, the 15 type-isolates of the VCGs and 342 atoxigenic isolates of the almond population. There was considerable genetic diversity among isolates with a lack of differentiation among micro-geographical regions or years. Since isolates sharing identical SSR profiles from distinct orchards were rare, we separated them into groups of at least 3 closely-related isolates from distinct orchards that shared identical alleles for at least 15 out of the 17 loci. This led to the identification of 15 groups comprising up to 24 closely-related isolates. The group which contained the largest number of isolates were members of YV36 while five groups were also found to be members of our studied atoxigenic VCGs. These results suggest that these 15 groups, and AF36 in particular, are well adapted to various environmental conditions in California and to tree crops and, as such, are good candidates for use as biocontrol agents. [ABSTRACT FROM AUTHOR]

Orchards consist of complex agricultural systems, with a variety of characteristics (planting density, tree height, training system, canopy cover, irrigation method, interrow management) influencing crop evapotranspiration (ET c). Thus, irrigation water management requires finding crop coefficients (K c) that represent the characteristics of local orchards, evidencing the need for site specific data. The main objective of this study was to derive the K c of almond, olive, citrus, and pomegranate orchards in Alentejo, southern Portugal, wherein they became dominant over the last decade. Monitoring was carried out in nine orchards, which management decisions were performed by the farmers. The ET c was estimated from the soil water balance computed for each orchard using the FAO56 dual-K c approach with the SIMDualKc model. The model successfully simulated the soil water contents measured in the various fields along two growing seasons, with root mean square error values lower than 0.005 m3 m−3 and modeling efficiencies from 0.363 to 0.782. The estimated basal crop coefficients (K cb) for the initial, mid- and end-seasons were respectively 0.22, 0.58, and 0.50 for almond; 0.32–0.33, 0.35–0.36, and 0.33–0.34 for olive; 0.40, 0.40–41, and 0.40–0.41 for citrus; and 0.24, 0.60, and 0.52 for pomegranate. Small variations in olive and citrus K cb values were found to be related to differences in the fraction of the ground covered by trees' canopies and tree height. The single K c values, which included the component relative to soil evaporation, were also estimated. Furthermore, evaluation of the soil water balance in the nine case studies showed salinity effects in one almond orchard, mild irrigation water deficits in olive systems, and large non-consumptive water use in citrus and pomegranate orchards. These results evidence the need for better management of orchards irrigation water in the region, and the current study provides for reliable information on the K c of tree crops to support improving the management of local orchard systems and the preservation of soil and water resources. Aimed at these resources and the sustainability of their use, simulated alternative irrigation schedules were performed, which identified possible water savings of 20 mm in case of olives, up to 855 mm for citrus. • Irrigation management in nine commercial orchards was assessed with SIMDualKc. • Large non-consumptive water use was found in almond, citrus and pomegranate orchards. • Olive systems registered mild irrigation water deficits. • K c values are provided for improving irrigation water management in the Alentejo region. • Better training of orchardists is needed with support of computational tools. [ABSTRACT FROM AUTHOR]

Accurate, spatially extensive, and frequent assessments of plant nitrogen (N) enabled by remote sensing allow growers to optimize fertilizer applications and reduce environmental impacts. Standard remote sensing methods for N assessment typically involve the use of chlorophyll-sensitive vegetation indices calculated from multispectral or hyperspectral reflectance data. However, the chlorophyll a + b derived from spectral indices is indirectly related to leaf N and saturates at high leaf N levels, dramatically reducing the sensitivity with leaf N under these conditions. Furthermore, these relationships are heavily influenced by canopy structure, variability in leaf area density, proportion of sunlit-shaded tree-crown components, soil background, and understory. Recent studies in uniform crops have demonstrated that estimation of plant N can be improved by considering leaf biochemical constituents derived from radiative transfer model (RTM) and solar-induced fluorescence (SIF). However, it is unclear whether these methods are transferable to tree crops due to their intrinsic physiological differences, structural complexity, and within-tree crown heterogeneity. We investigated how various hyperspectrally derived proxies for leaf N, including RTM-based traits and SIF, could be combined to assess N status on a 1200-ha almond orchard across two growing seasons. RTM-based chlorophyll a + b content (C ab) and SIF were found to be the most important and consistent predictors for leaf N compared to other leaf biochemical and biophysical traits. C ab alone was a modest predictor of leaf N variability (r 2 = 0.49, RMSE = 0.16%, p -value <0.001), but when the non-collinear SIF and C ab traits were coupled together, predictions improved dramatically (r 2 = 0.95, RMSE = 0.05%, p -value <0.001). Leaf area index (LAI) was poorly associated with leaf N, suggesting that leaf physiological traits may be more important than structural traits in quantifying leaf N in well-managed orchards characterized by high N levels. Consistent results across the 2 years suggests the importance of airborne SIF coupled with C ab for precision agriculture and leaf N status assessment in almond orchards. • Image-derived leaf N significantly improves when adding SIF to the RTM-derived C ab. • C ab and SIF were the most important predictors of leaf N variability observed in an almond orchard. • C ab with SIF explained 95% of the leaf N variability across 2 years of airborne data collection. • RTM-derived biochemistry correlated better with leaf N than traditional indices such as NDVI. • SIF is critical for accurate leaf N estimation in well-managed crops characterized by high N levels. [ABSTRACT FROM AUTHOR]

Evapotranspiration (ET), a key component of crop water balance, is essential for growers to manage agricultural irrigation. METRIC model is increasingly used to estimate and map ET with satellite observations, especially at daily and field scales. However, the analysis of its uncertainties on tree crop ET estimation is very limited. We used METRIC model to estimate daily ET over the almond and pistachio orchards throughout the entire growing season in the San Joaquin Valley, California, and evaluated the impacts of variations in meteorological variables, land surface parameters and different study sizes on ET estimation. The results showed that the METRIC-based daily ET estimates of the almond and pistachio trees were most sensitive to net radiation (Rn), followed by instantaneous reference ET (ETo), land surface temperature (LST), and near-surface temperature difference (dT). When a 5% error was added to Rn, the uncertainty in daily ET estimates was up to 8.44 ± 1.24%, corresponding to a mean increase of 0.45 ± 0.02 mm/day throughout the entire growing season. A 5% or 0.5 K error in instantaneous ETo, LST, and dT also caused changes in daily ET estimates by 4.15 ± 3.75%, 2.97 ± 0.14%, and 2.31 ± 1.20%, respectively. ET estimates with METRIC were relatively much less sensitive to other variables. The results from different study sizes indicated that daily ET estimates in Size-2 were 0.33 ± 0.08 mm/day overestimation compared with those from Size-1 in the almond site. Similarly, a mean overestimation of 0.30 ± 0.14 mm/day was found between Size-1 and Size-3 in the pistachio sites throughout the entire growing season. This study demonstrates the potential to further improve the accuracy of remote sensing based ET estimation for complex tree crops with METRIC model, by optimizing key parameters and choosing a proper domain size for study area. • Daily evapotranspiration of tree crops was estimated by METRIC model. • The impacts of variation in meteorological variables on METRIC-based ET were evaluated throughout the entire growing seasons. • The impacts of variation in land surface parameters on METRIC-based ET were assessed throughout the entire growing seasons. • The impact of varying study sizes on METRIC-based ET estimates was tested. [ABSTRACT FROM AUTHOR]

Homogeneous tree crop plantations can adversely impact wild pollinator communities by limiting the temporal continuity of food and the availability of nesting sites. Identifying how structural differences between plantations and natural vegetation influence pollinator communities is necessary for ecological management of agroecosystems., Communities of potential wild pollinators (native bees, wasps, flies) were compared between monoculture almond plantations and native vegetation in a semi-arid region of southern Australia, before, during and after the late winter almond flowering period. Abundance and richness of each insect group were related to site heterogeneity and keystone structural resources at each site, focusing on food and nesting resources., Relationships with site heterogeneity varied between taxa and across months. Native bee abundance and richness were strongly associated with specific keystone resources, despite showing no association with site heterogeneity., The present study highlights the value of focusing on biologically meaningful resources when investigating relationships between insects and habitat, rather than on generalized heterogeneity metrics. The results suggest that maintaining keystone resources in agroecosystems can support the conservation of insects and ecosystem services, especially in areas where homogeneous agricultural systems overlap dynamic natural ecosystems. [ABSTRACT FROM AUTHOR]

• Peach is entering a period of transformation driven by changes in climate, production methods and market trends but where future breeding progress is severely limited by its very narrow genetic base. • Peach rootstocks primarily utilize interspecies hybrids to successfully incorporate needed traits for disease, pest and environmental stress resistance. • Interspecies hybridizations resulting in commercially successful rootstocks have been made between cultivated peach and its close wild peach relatives, as well as the more distantly related cultivated almond and its numerous and ecologically diverse wild relatives. • Hybrids between peach and plum as well as apricot species have also been successful, though more difficult. • Recent efforts to further introgress such exotic germplasm for peach cultivar improvement have successfully transferred not only disease and pest resistance but also improved fruit and tree quality as well as greater tolerance to environmental stresses. Peach, a major fresh-market and processing tree crop world-wide, is entering a period of transformation driven by changes in climate, production methods and market trends but where future breeding progress is severely limited by its very narrow genetic base. Peach rootstocks, which are also of global importance, have a long history of utilizing interspecies hybridization to successfully incorporate needed traits for disease, pest and environmental stress resistance. Interspecies hybridizations resulting in commercially successful rootstocks have been made between cultivated peach and its close wild peach relatives, as well as the more distantly related cultivated almond and its numerous and ecologically diverse wild relatives. Hybrids between peach and plum as well as apricot species have also been successful, though more difficult. Recent efforts to further introgress such exotic germplasm for peach cultivar improvement have successfully transferred not only disease and pest resistance but also improved fruit and tree quality as well as greater tolerance to environmental stresses. Associated genetic and genomic studies provide useful information on trait heritability and, in many cases, have identified putative linkage group and possible candidate genes. Heritability of most traits derived from exotic germplasm, however, remains poorly studied, though early research suggests genomic and epigenetic modifications may sometimes be involved in addition to more traditionally studied genetic changes. While exotic gene introgression has the potential for transferring novel traits of value for rootstock and cultivar improvement, undesirable but undetected changes can also occur that, because of the long-lived and high-value nature of peach orchards, can ultimately result in severe economic losses. [ABSTRACT FROM AUTHOR]

Large-scale single-pass sequencing of expressed sequence tags (ESTs) can give a global picture of the genes involved in the development and function of organs and tissues. Almond (Prunus dulcis Mill. syn. Amygdalus communis L. var. dulcis) is a self-incompatible fruit tree of the family Rosaceae. As an attempt to examine the transcripts expressed during pistil development, we randomly selected and partially sequenced over 1,000 clones from a cDNA library of almond pistils. Analysis of the ESTs using the NCBI non-redundant protein database revealed that 456 (~45.4%) have significant similarity to protein coding sequences in the database. Among the 549 cDNAs with no similarity to known protein sequences, 56 clones have significant similarity to nucleotide sequences registered in the databases. Sequences were assembled using StackPACK and the estimated number of genes identified was 716: 121 contigs and 595 singletons. Only eight of the unique cDNA clones correspond to previously isolated gene sequences of P. dulcis. After functional classification of almond ESTs, "stress resistance and defense" and "protein synthesis and processing" ESTs were found to be the most numerous. Our EST analysis provides a first picture of the numerous almond genes potentially involved in pistil development. It also contributes to our knowledge about gene expression patterns in pistils while providing an extensive reservoir for gene cloning and genetic mapping in almond and other related fruit trees. [ABSTRACT FROM AUTHOR]

Breeding programs for horticultural tree crops focus on enhancing productivity, including developing tolerance to pests and diseases and improving crop quality. Pollination services are often critical for crop production, and pollen parents can affect crop quality. We often do not know which pollen parents produce highest quality offspring or, in self-compatible cultivars, how much of the crop comes from cross- versus self-pollination. We quantified the proportions of self- and cross-paternity in an open pollination setting of five standard commercial almond cultivars and of six new almond cultivars selected for yield, kernel size, taste or self-compatibility. We assessed how pollination by different parents affected kernel size and nutritional quality. Kernels from most commercial cultivars and from the new cultivars selected for taste and size resulted almost entirely from cross-pollination. Most kernels from the commercial cultivar 'Price' resulted from cross-pollination but 21% resulted from self-pollination. In contrast, 48–91% of kernels from the new self-compatible cultivars resulted from self-pollination. Different cross-pollen parents did not greatly affect kernel size or quality. The proportions of self-paternity in the new self-compatible cultivars varied strongly in an open pollination setting suggesting that some cultivars may be good candidates for establishing monovarietal orchards. [ABSTRACT FROM AUTHOR]

• The assessment of climate change impact on almond revealed major uncertainties • Dynamic Model & ASYMCUR approach used to estimate bloom dates of 15 almond cultivars • High spatial and temporal variability in bloom is expected in Iberian Peninsula (IP) • Chill accumulation and frost damage are expected to decrease in the future in IP • Spatial analysis of hazards can inform cultivar selection for effective adaptation The assessment of the impact of climate change on Mediterranean crop systems is affected by a large number of uncertainties. To overcome this issue in an impact and adaptation assessment for tree crops, an experimental dataset containing 556 phenological observations was used to calibrate and validate a modelling framework based on the Dynamic Model and ASYMCUR approach, for assessing the flowering date of common Mediterranean almond cultivars. Data were collected over 12 years for 15 almond cultivars in 5 locations in Andalusia (Southern Spain), covering a wide range of weather conditions. The model performance was good: for late-flowering cultivars Root Mean Square Error (RMSE) was 3.6 days and Nash-Sutcliffe model efficiency (NSE) was 0.89, while for early-flowering cultivars RMSE was 3.4 days and NSE was 0.83. Weather projections from an ensemble of 12 climate model outputs including 3 Representative Concentration Pathways (RCPs) were used with the modelling framework for each almond cultivar to quantify the changes in flowering date and the associated weather conditions during this stage, under the future weather conditions of the Iberian Peninsula (IP). Thus, in future scenarios, depending on location, start of full bloom was delayed (in mild-winter areas) or advanced (in cold-winter areas), with the change in weather conditions during critical phenological stages potentially affecting the yield in different ways, depicting a high spatial variability in the projections within the IP. For this reason, a spatial analysis was applied to demarcate those areas with adverse weather conditions related to flowering stage. In light of our results it is concluded that the identification of impacts and adaptation strategies for Mediterranean agriculture requires a careful prior evaluation of the systems at local scale, due to the marked spatial heterogeneity and the remaining high uncertainties associated with the crop modelling. [ABSTRACT FROM AUTHOR]

• The relative transpiration of almond trees was related to CWSI. • It fitted the theory developed by Jackson et al. (1981) , but showed a large scatter. • The work discusses the probable causes of the scatter. • It evaluates the use of transpiration derived from CWSI for the irrigation management. There is growing interest in the use of canopy temperature to evaluate the water status of crops for irrigation water management. One of the main indicators currently used is the Crop Water Stress Index (CWSI). In this index, the canopy temperature is normalized by the environmental conditions to account for the evaporative demand of the atmosphere. The theoretical framework, based on the Penman-Monteith equation, defined the CWSI as one minus the ratio between actual and potential water use (Jackson et al., 1981). For the first time in tree crops, we have related the actual transpiration of almond trees measured with heat-pulse sap flow probes with the CWSI, calculated using an empirical Non-Water Stress Baseline. The relationship obtained between the CWSI and the relative transpiration fitted the theoretical relationship, although it showed a large scatter (R2=0.69; RMSE=0.13). The variability in micrometeorological conditions among different parts of the canopy, the scatter of the NWSB, or inherent measurement errors are identified as probable causes of this scatter. Finally, the effect of this scatter on the accurate assessment of actual transpiration from canopy temperature is analyzed for practical irrigation management purposes. We found an error of about 10% in the relative transpiration, which seems acceptable for irrigation management applications. [ABSTRACT FROM AUTHOR]

• Overall accuracy of crop classification reaches 85 %–90 % by using full year UAVSAR. • Polarimetric parameters contribute more than linear polarizations to crop mapping. • The CP parameters are much more important than the FD parameters for crop mapping. • The combined use of four acquisitions is adequate to achieve a nearly optimal accuracy. Accurate and timely information on the distribution of crop types is vital to agricultural management, ecosystem services valuation and food security assessment. Synthetic Aperture Radar (SAR) systems have become increasingly popular in the field of crop monitoring and classification. However, the potential of time-series polarimetric SAR data has not been explored extensively, with several open scientific questions (e.g. the optimal combination of image dates for crop classification) that need to be answered. In this research, the usefulness of full year (both 2011 and 2014) L-band fully-polarimetric Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) data in crop classification was fully investigated over an agricultural region with a heterogeneous distribution of crop categories. In total, 11 crop classes including tree crops (almond and walnut), forage crops (grass, alfalfa, hay, and clover), a spring crop (winter wheat), and summer crops (corn, sunflower, tomato, and pepper), were discriminated using the Random Forest (RF) algorithm. The SAR input variables included raw linear polarization channels as well as polarimetric parameters derived from Cloude-Pottier (CP) and Freeman-Durden (FD) decompositions. Results showed clearly that the polarimetric parameters yielded much higher classification accuracies than linear polarizations. The combined use of all variables (linear polarizations and polarimetric parameters) produced the maximum overall accuracy of 90.50 % and 84.93 % for 2011 and 2014, respectively, with a significant increase of approximately 8 percentage points compared with linear polarizations alone. The variable importance provided by the RF illustrated that the polarimetric parameters had a far greater influence than linear polarizations, with the CP parameters being much more important than the FD parameters. The most important acquisitions were the images dated during the peak biomass stage (July and August) when the differences in structural characteristics between most crops were the largest. At the same time, the images in spring (April and May) and autumn (October) also contributed to the crop classification since they respectively provided unique information for discriminating fruit crops (almond and walnut) as well as summer crops (corn, sunflower, and tomato). As a result, the combined use of only four acquisitions (dated May, July, August, and October for 2011 and April, June, August, and October for 2014) was adequate to achieve a nearly-optimal overall accuracy. In light of the promising classification accuracies demonstrated in this research, it becomes increasingly viable to provide accurate and up-to-date crops inventories over large areas based solely on multitemporal polarimetric SAR. [ABSTRACT FROM AUTHOR]

An integrated assessment of crop-energy-water (CEW) nexus is critical to understand the tradeoffs and synergies for better management of sustainable agricultural systems. In this study, we evaluate the historic evolution of CEW interactions in the Central Valley, California, a critical agricultural region that produces approximately 50% of US fruits, nuts and vegetables. Specifically, we consider three nexus elements, including water use for irrigation (blue water), energy use for groundwater pumping, and crop yield (for all crops aggregated, almond and cotton). To quantify the interactions between CEW elements, we estimate the water use for cropping (water footprint) and energy use for cropping (energy footprint). We conduct the analyses for four historical periods, i.e., 2007–2009 (Drought 1), 2010–2011 (Post-drought 1), 2012–2015 (Drought 2) and 2016–2018 (Post-drought 2). We find that the southern regions (San Joaquin and Tulare) are susceptible to greater stress on energy and water, especially during droughts. The groundwater footprint (GWF) has been continuously increasing due to greater crop water use and a shift from row crops to profitable water-intensive tree crops. The GWF in Tulare during Drought 2 was around 60% higher than Drought 1, where the GWF in Tulare was almost twice that of Sacramento. The energy and water uses for almond production have increased during the recent periods, whereas their uses have mostly decreased for cotton. On average, energy and water footprints under almond crop scenario are around 3–3.5 times as much as the footprints under all crops scenario. [ABSTRACT FROM AUTHOR]