Pablo J. Zarco-Tejada

• PhD Earth & Space Science
• Research Scientist at Spanish National Research Council

Radiata pine (Pinus radiata D. Don) is a widely planted tree species. Fertilizers, especially those containing leaf nitrogen (N) and phosphorous (P), are essential for maximizing growth. Nutrient deficiencies and excessive fertilization can limit growth, so monitoring is crucial. Leaf pigments such as chlorophyll a+b (C a+b) can be used to assess p...

Introduction Optimizing fruit quality and yield in agriculture requires accurately monitoring leaf nitrogen (N) status spatially and temporally throughout the growing season. Standard remote sensing approaches for assessing leaf N rely on proxies like vegetation indices or leaf chlorophyll a + b (Cab) content. However, limitations exist due to the...

High-throughput phenotyping (HTP) provides new opportunities for efficiently dissecting the genetic basis of drought-adaptive traits, which is essential in current wheat breeding programs. The combined use of HTP and genome-wide association (GWAS) approaches has been useful in the assessment of complex traits such as yield, under field stress condi...

Remote sensing is obtaining information about an object without physical contact, typically carried out with sensors onboard satellites, aircraft, or land-based platforms. Today, several technologies can be integrated into these carriers to map and monitor different plant biophysical traits with high spatial and temporal resolution. New sensors and...

Hyperspectral imaging of solar-induced chlorophyll fluorescence (SIF) is required for plant phenotyping and stress detection. However, the most accurate instruments for SIF quantification, such as sub-nanometer (≤1-nm full-width at half-maximum, FWHM) airborne hyperspectral imagers, are expensive and uncommon. Previous studies have demonstrated tha...

Detecting plant pathogens and diagnosing diseases are critical components of successful pest management. These key areas have undergone significant advancements driven by breakthroughs in molecular biology and remote sensing technologies within the realm of precision agriculture. Notably, nucleic acid amplification techniques, with recent emphasis...

Global agriculture faces increasing pressure to produce more food with fewer resources. Drought, exacerbated by climate change, is a major agricultural constraint costing the industry an estimated US$80 billion per year in lost production. Wild relatives of domesticated crops, including wheat (Triticum spp.) and barley (Hordeum vulgare L.), are an...

Integrating far-red solar-induced chlorophyll fluorescence (SIF 760 ) and leaf biochemical constituents (primarily leaf chlorophyll content (C a+b )) has recently been demonstrated to improve the estimation of leaf nitrogen (N) concentration from airborne and spaceborne hyperspectral imagery in homogenous and heterogeneous crop canopies. The advent...

Dothistroma needle blight, caused by the fungi Dothistroma septosporum and D. pini is globally one of the most damaging diseases of pine species. Infection from the pathogen, which is initiated in the lower crown, causes needle chlorosis, loss of cellular integrity, necrosis and premature needle loss with this developmental sequence impacting key p...

Solar-induced chlorophyll fluorescence (SIF) is a remotely sensed optical signal emitted during the light reactions of photosynthesis. The past two decades have witnessed an explosion in availability of SIF data at increasingly higher spatial and temporal resolutions, sparking applications in diverse research sectors (e.g., ecology, agriculture, hy...

Early prediction of crop production by remote sensing (RS) may help to plan the harvest and ensure food security. This study aims to improve the quantification of yield, grain protein concentration (GPC), and nitrogen (N) output in winter wheat with RS imagery. Ground-truth wheat traits were measured at flowering and harvest in a field experiment c...

Although our observing capabilities of solar‐induced chlorophyll fluorescence (SIF) have been growing rapidly, the quality and consistency of SIF datasets are still in an active stage of research and development. As a result, there are considerable inconsistencies among diverse SIF datasets at all scales and the widespread applications of them have...

Xylella fastidiosa is a major transboundary plant pest, causing severe socioeconomic impacts. Development of preventive strategies and methods for surveillance, early detection, monitoring, and accurate diagnosis of X. fastidiosa and its vectors, are keys to preventing the effects of this plant pathogen, and assist timely eradication or optimisatio...

Wheat (Triticum spp.) is among the world’s most widely grown crops and receives large quantities of nitrogen (N) fertiliser. Grain protein content (GPC) is influenced by genetic, agronomic and weather conditions affecting crops’ physiological status and stress levels; accurate GPC prediction has potential to reduce N losses and improve profit. Succ...

Canopy temperature is generally accepted as an indirect but rapid, accurate, and large-scale indicator of crop water status and is, therefore, proposed to monitor irrigation needs. Crop Water Stress Index (CWSI) is the most widely used among the existing thermal-based indicators, and its links with water stress have been demonstrated. When calculat...

Sub-nanometer hyperspectral imagers are increasingly being used to quantify solar-induced chlorophyll fluorescence (SIF) due to their ability to characterize narrow absorption features accurately. However, some limitations prevent their wide use in the operational context due to their high cost, weight, and complexity. On the other hand, more widel...

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 hyperspect...

Solar-induced chlorophyll fluorescence (SIF) can be used as an indicator of crop photosynthetic activity and a proxy for vegetation stress in plant phenotyping and precision agriculture applications. SIF quantification is sensitive to the spectral resolution (SR), and its accurate retrieval requires sensors with sub-nanometer resolutions. However,...

The thermal region of the electromagnetic spectrum might provide valuable information for assessing plant water status. Nevertheless, the plant's physiology and the scale of measurement, (e.g. sensor viewing geometry and the canopy aggregation) are critical for quantifiying and monitoring water stress. This study compares the Crop Water Stress Inde...

Multiple and heterogenous Earth observation (EO) platforms are broadly used for a wide array of applications, and the integration of these diverse modalities facilitates better extraction of information than using them individually. The detection capability of the multispectral unmanned aerial vehicle (UAV) and satellite imagery can be significantl...

The development of methods to spatially describe long-term water stress in plantations is going to become increasingly important as drought events increase in frequency under climate change. Despite this we are unaware of any research that has used hyperspectral imagery to describe long-term water stress for the most widely established exotic pine...

Plant pathogens pose increasing threats to global food security, causing yield losses that exceed 30% in food-deficit regions. Xylella fastidiosa ( Xf ) represents the major transboundary plant pest and one of the world’s most damaging pathogens in terms of socioeconomic impact. Spectral screening methods are critical to detect non-visual symptoms...

Fuente obejuna-Córdoba-españa (Progetto aei Feder har 77136-r) Aerial Thermic Teledection and "Smart Archaeology" around the roman city of Mellaria (AltoGuadiato-Córdoba-España) Established in the LII mile of the Roman road from Córdoba to Mérida, Mellaria is the only Roman city that exists in the current administrative border between the Spanish r...

Accurate nitrogen (N) assessment is crucial for precise and sustainable agricultural management. Understanding crop nutrient status in a timely manner is essential to improve the efficiency of fertilizer application throughout the growing season across the entire farm. Standard remote sensing methods for N assessment are built upon empirical relati...

Holm oak decline is a complex phenomenon mainly influenced by the presence of Phytophthora cinnamomi and water stress. Plant functional traits (PTs) are altered during the decline process — initially affecting the physiological condition of the plants with non-visual symptoms and subsequently the leaf pigment content and canopy structure — being it...

Globally, olive (Olea europaea L.) productivity is threatened by plant pathogens, particularly the fungus Verticillium dahliae (Vd) and the bacterium Xylella fastidiosa (Xf). Infections by these pathogens restrict water and nutrient flow through xylem, producing a similar set of symptoms that can also be confounded with water stress. Conventional i...

Adjusting nitrogen (N) fertilization and accounting for the legacy of past N fertilizer application (i.e., residual N) based on remote sensing estimation of crop nutritional status may increase resource efficiency and promote sustainable management of cropping systems. Our main goal was to evaluate the potential of hyperspectral airborne imagers an...

Together with ensuring a stable yield, improving grape composition and aroma is the main goal of wine grape production management as it determines consumer acceptance and ultimately revenue. Understanding the triggers of the synthesis of aromatic components and finding methods to map their variability in the field can aid management practices durin...

Standard remote sensing methods for nitrogen (N) assessment in precision agriculture rely on empirical relationships built with chlorophyll a+b (Cab) sensitive vegetation indices. Nevertheless, methods of N estimation based on the Cab vs. N relationships are strongly affected by the saturation of these indices at high N levels, and by canopy struct...

Several studies have demonstrated the influence of the spectral resolution (SR) on the retrieval of solar-induced chlorophyll fluorescence (SIF) from ground-based sensors with different spectral configurations. However, research studying the implications of the SR of airborne hyperspectral imagers on the retrieved SIF is lacking, and its interpreta...

Remote sensing is a valuable tool for reducing the environmental impact of agricultural practices by detecting crop nitrogen (N) and water status for site-specific N fertilization and irrigation. The interaction between N and water status may produce confounding effects in the acquired spectral reflectance, making it difficult to separate crop defi...

A R T I C L E I N F O Keywords: Hyperspectral Thermal Epidemic spread model Radiative transfer model SWIR domain Xylella fastidiosa Nitrogen Machine learning A B S T R A C T The early detection of Xylella fastidiosa (Xf) infections is critical to the management of this dangerous plan pathogen across the world. Recent studies with remote sensing (RS...

This paper presents a novel methodology for identifying homogeneous areas within high-frequency drip-irrigated orchards and for defining the most sensitive and resistant areas of the field to water stress. The methodology proposed here is based on the assessment of water status at the tree level during mild water stress using remote sensing derived...

In the last decade, unmanned aerial vehicles (UAVs/UAS/RPAS) have been proposed for agricultural applications due to their great flexibility in flight scheduling and the increasing availability of dedicated miniaturized sensors. The capability of these systems in determining biophysical and geometrical parameters was tested in olive (Olea europaea...

The downside risk of crop production affects the entire supply chain of the agricultural industry nationally and globally. This also has a profound impact on food security, and thus livelihoods, in many parts of the world. The advent of high temporal, spatial and spectral resolution remote sensing platforms, specifically during the last five years,...

The leaf maximum carboxylation rate (Vcmax) is a key parameter in modelling plant photosynthesis. The rapid and accurate acquisition of Vcmax at large scales can improve understanding of global vegetation productivity and the terrestrial carbon cycle. In this study, we assessed the retrieval of Vcmax from satellite data by validating these data usi...

Remote sensing efforts made as part of European initiatives via POnTE, XF-ACTORS and the JRC, as well as through regional programs, have focused, among others, on the development of algorithms for the early detection of Xylella fastidiosa (Xf)-induced symptoms. Airborne campaigns carried out between 2016 and 2019 collected high-resolution hyperspec...

Field-scale imaging spectroscopy for measuring nutrients and photosynthesis parameters. Correlation of N and P to Vcmax and Jmax only exists in N- (respective P-) limited trees.

Significant advances toward the remote sensing of photosynthetic activity have been achieved in the last decades, including sensor design and radiative transfer model (RTM) development. Nevertheless, finding methods to accurately quantify carbon assimilation across species and spatial scales remains a challenge. Most methods are either empirical an...

A major international effort has been made to monitor sun-induced chlorophyll fluorescence (SIF) from space as a proxy for the photosynthetic activity of terrestrial vegetation. However, the effect of spatial heterogeneity on the SIF retrievals from canopy radiance derived from images with medium and low spatial resolution remains uncharacterised....

Spatial prediction of photosynthesis requires an understanding of how foliage nitrogen (N) and phosphorus (P) regulate this process and the relationship between these elements and scalable spectral proxies. Hyperspectral imagery has been used to predict important photosynthetic variables such as the maximum rate of carboxylation (Vcmax) and electro...

The prediction of carbon uptake by forests across fertility gradients requires accurate characterisation of how biochemical limitations to photosynthesis respond to variation in key elements such as nitrogen (N) and phosphorus (P). Over the last decade, proxies for chlorophyll and photosynthetic activity have been extracted from hyperspectral image...

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...

Crop yields need to be improved in a sustainable manner to meet the expected requirements of the worldwide increase in population in the coming decades and with anticipated climate change. Genomics-assisted breeding has become popular in recent years as an approach to contribute to food security, and in this regard, the crop breeding community need...

Xylella fastidiosa (Xf) is a harmful plant pathogenic bacterium, able to infect over 500 plant species worldwide. Successful eradication and containment strategies for harmful pathogens require large-scale monitoring techniques for the detection of infected hosts, even when they do not display visual symptoms. Although a previous study using airbor...

Outbreaks of Xylella fastidiosa (Xf) in Europe generate considerable economic and environmental damage, and this plant pest continues to spread. Detecting and monitoring the spatio-temporal dynamics of the disease symptoms caused by Xf at a large scale is key to curtailing its expansion and mitigating its impacts. Here, we combined 3-D radiative tr...

Purpose of Review We provide a comprehensive review of the empirical and modelling approaches used to quantify the radiation–vegetation interactions related to vegetation temperature, leaf optical properties linked to pigment absorption and chlorophyll fluorescence emission, and of their capability to monitor vegetation health. Part 1 provides an o...

Effective collaboration depends on an individual’s willingness to interact and share knowledge for generating solutions to complex theoretical or applied problems. These traits are especially important when problems are unlikely to be solved within the conceptual framework of a single discipline. The application of remote sensing methods in plant p...

Unlike satellite earth observation, multispectral images acquired by Unmanned Aerial Systems (UAS) provide great opportunities to monitor land surface conditions also in cloudy or overcast weather conditions. This is especially relevant for high latitudes where overcast and cloudy days are common. However, multispectral imagery acquired by miniatur...

Photosynthesis is essential for life on earth as it, inter alia, influences the composition of the atmosphere and is the driving mechanism of primary production. Photosynthesis is particularly controlled by leaf pigments such as chlorophyll, carotenoids or anthocyanins. Incoming solar radiation is mainly captured by chlorophyll, whereas plant organ...

Agriculture faces the challenge of providing food, fibre and energy from limited land resources to satisfy the changing needs of a growing world population. Global megatrends, e.g., climate change, influence environmental production factors; production and consumption thus must be continuously adjusted to maintain the producer–consumer-equilibrium...

Plant photosynthetic traits may be indicative of stress tolerance and performance in the field, making their accurate assessment critical in phenotyping trials. The maximum rate of carboxylation (Vcmax)is a key parameter for estimating CO2 assimilation (A), as it controls the CO2 fixation rate. This study demonstrates the utility of combining airbo...

With the advent of Sentinel-2, it is now possible to generate large-scale chlorophyll content maps with unprecedented spatial and temporal resolution, suitable for monitoring ecological processes such as vegetative stress and/or decline. However methodological gaps exist for adapting this technology to heterogeneous natural vegetation and for trans...

Wheat can adapt to most agricultural conditions across temperate regions. This success is the result of phenotypic plasticity conferred by a large and complex genome composed of three homoeologous genomes (A, B, and D). Although drought is a major cause of yield and quality loss in wheat, the adaptive mechanisms and gene networks underlying drought...

This paper evaluates the usefulness of the Crop Water Stress Index (CWSI) for monitoring transpiration and water status in almond trees, and proposes a methodology for assessing crop yield derived from the relation between canopy temperature and transpiration. For this purpose, a Non-Water Stress Baseline (NWSB) was developed from canopy temperatur...

Climatic conditions affect the growth, development and final crop production. As wheat is of paramount importance as a staple crop in the human diet, there is a growing need to study its abiotic stress adaptation through the performance of key breeding traits. New and complementary approaches, such as genome-wide association studies (GWAS) and geno...

Site location and agronomical details. (XLSX)

Descriptive statistics of each trait in each environment with key quantiles. (XLSX)

Accession mean values and standard deviation for assessed traits by year and location. (IAS, initial agronomic score; WGP, whole grain protein (%); SW, specific weight (g); YC, yellow colour; GI, gluten index (%); SDS, sedimentation index (cm3); and YIELD, yield (Kg/ha)). Means were calculated for three replications of the durum varieties at the fi...

Analysis of candidate genes found in Glu-A1 and Glu-B1 loci in chromosomes 1A and 1B. Differentially expression was indicated for each gene: SFS—severe stress field conditions; MFS—mild field stress conditions; P1h - osmotic stress as polyethylene glycol (PEG) 1hour; P6h - osmotic stress PEG 6hours. (TIFF)

Relationship between yield and temperature. a) Relation between yield and maximum temperature mean (°C) by location and year for durum wheat varieties for final stages; b) Relation between yield and thermal sum from 1st April to 30th June. (YIELD: mean values by place and year for released lines (Kg/ha); Tmax: maximum temperature (°C); GDD: Growing...

Kindship matrix for DArT markers. (XLSX)

Kindship matrix for SNP markers. (XLSX)

List of durum wheat lines assessed. (XLSX)

Projection of each genotype assessed on all the PCos. (XLSX)

Eigenvalues from the PCo analysis. (XLSX)

BLUP analysis results using DArT markers for assessed traits (gluten index, GI; initial agronomic score, IAS; sedimentation index, SDS; specific weight, SW; whole grain protein, WGP; yellow colour, YC; yield, YIELD). (XLSX)

Meteorological information collected from agroclimatic stations (Junta de Andalucia) (https://www.juntadeandalucia.es/agriculturaypesca/ifapa/ria/servlet/ FrontController). Mean, maximum and minimum values for temperature (maximum temperature (Tmax), average temperature (Tmed) and minimum temperature (Tmin)) (°C), rainfall (Pp) (mm) and evapotransp...

Matrix of correlations between assessed traits across years and environments (yield (Kg/ha), YIELD; yellow colour, YC; whole grain protein (%), WGP; specific weight (g), SW; sedimentation index (cm3), SDS; initial agronomic score, IAS; and gluten index (%), GI). (XLSX)

BLUP analysis results using SNP markers for assessed traits (gluten index, GI; initial agronomic score, IAS; sedimentation index, SDS; specific weight, SW; whole grain protein, WGP; yellow colour, YC; yield, YIELD). (XLSX)

The recent technical improvements in the sensors used to acquire images from land surfaces has made possible to assess the performance of the energy balance models using unprecedented spatial resolutions. Thus, the objective of this work is to evaluate the response of the different energy balance components obtained from METRIC model as a function...

The experiments were conducted in a fully-productive olive orchard (cv. Frantoio) at the experimental farm of University of Pisa at Venturina (Italy) in 2015 to assess the ability of an unmanned aerial vehicle (UAV) equipped with RGB-NIR cameras to estimate leaf area index (LAI), tree height, canopy diameter and canopy volume of olive trees that we...

The relationship between NDVI and leaf chlorophyll on DOY 130 in 2015. Irrigation period lasted from DOY 182 through DOY 273 in 2015. Each symbol represents one tree. Different symbols are used to distinguish the two groups of trees before the beginning of the irrigation treatments. Filled dots and open symbols represent irrigated and rainfed trees...

The relationship between SPAD and leaf chlorophyll. Data were acquired on DOY 130 in 2015 in olive trees before the beginning of the irrigation treatments (irrigation vs rainfed). Each symbol represents one tree. (PDF)

Europe’s major X. fastidiosa outbreaks have progressed steadily in the past years as data on the bacterial strains causing them, and on the host range and vectors of the pathogen in various regions, became available. The initial uncertainty around these critical epidemiological aspects of the X. fastidiosa invasions hampered estimates of their rate...

This work focuses on understanding the effects caused by the within-tree structural heterogeneity on the Crop Water Stress Index (CWSI). We present an assessment of the CWSI variability and its relationship with stomatal conductance (Gs) using different automatic object-based tree-crown detection algorithms based on temperature quartile thresholds....

In the last 10 years, development in robotics, computer vision, and sensor technology has provided new spectral remote sensing tools to capture unprecedented ultra-high spatial and high spectral resolution with unmanned aerial vehicles (UAVs). This development has led to a revolution in geospatial data collection in which not only few specialist da...

Plant pathogens cause significant losses to agricultural yields and increasingly threaten food security 1 , ecosystem integrity and societies in general2-5. Xylella fastidiosa is one of the most dangerous plant bacteria worldwide, causing several diseases with profound impacts on agriculture and the environment 6 . Primarily occurring in the Americ...