About

Giulia Marino is an Assistant Professor and Cooperative Extension Specialist in Orchard Systems at the Department of Plant Sciences, UC Davis. She holds a Ph.D. from the University of Palermo, Italy, in Fruit and Forestry Tree Systems, earned in 2012, along with a Master’s and Bachelor’s degree in Agricultural Science from the same university. Her research investigates tree physiology with a focus on enhancing productivity, sustainability, and competitiveness of fruit orchard production systems in the context of a changing global environment. Her work includes understanding the impact of abiotic stresses such as climate change, water scarcity, and soil degradation on orchard productivity and water use efficiency, as well as studying the physiological basis of perennial crop vegetative and bearing patterns influenced by sink-source relationships and carbohydrate dynamics. Marino also characterizes the physiological and horticultural potential of genetic resources to adapt to increased planting density and mechanization. Her methods range from proximate and remote sensing techniques to classical physiological and biometeorological measurements, aiming to develop physiologically-based orchard management strategies. She is involved in current projects that focus on deficit irrigation strategies for California olive systems, winter dormancy identification in cherry orchards, and factors affecting pistachio hull maturity and performance under various soil conditions.

Research topics

• Biology
• Agronomy
• Environmental science
• Fishery
• Environmental engineering
• Horticulture

Selected publications

• Alkalization and cell wall remodeling mark the fruit abscission zone maturation in table olive

  Journal of Experimental Botany · 2026-05-22

  articleOpen access

  Abscission zones mediate organ separation through coordinated changes in cell wall architecture and intercellular signaling. To elucidate mechanisms of fruit abscission zone (FAZ) transitions preceding fruit detachment in the non-climacteric fruit olive (Olea europaea), we integrated physiological, transcriptomic, and cellular analyses during natural maturation and after ethylene treatment. A mesocarp-subtraction RNA-seq strategy uncovered a FAZ-enriched module of 733 genes, representing core regulators of FAZ maturation. Induction of β-1,3-glucanase genes corresponded with elevated glucanase activity and callose depletion at plasmodesmata, indicating increased symplastic signaling required to initiate the abscission. A previously undocumented rise in cytoplasmic and apoplastic pH of the olive FAZ, coupled with reduction of low-methylesterified homogalacturonan, represents a hallmark of pH-dependent wall remodeling. Transcriptomic enrichment of transporters and pH-responsive wall-modifying enzymes positions pH homeostasis as a central regulator upstream of wall reconfiguration. Concurrent activation of pectate lyases and key phenylpropanoid pathway enzymes suggests a dual remodeling trajectory involving reduction of de-methylesterified pectin, which weakens intercellular cohesion, and localized lignin deposition, defining the separation boundary. Our findings establish a conserved molecular circuit that confers ethylene competence to the FAZ and a mechanistic framework in which symplastic connectivity, pH-driven enzymatic activation, and modulation of wall polymer chemistry orchestrate FAZ maturation and fruit detachment in table olive.

  PublisherOA PDFDOI

• Effects of a seaweed biostimulant on physiology and productivity of mature almonds across tree water status

  Plant Stress · 2026-02-21

  articleOpen accessSenior author

  This study evaluated the effects of soil-applied Ascophyllum nodosum extract (ANE) on the physiology and productivity of a mature almond orchard managed under full and deficit irrigation. ANE consistently enhanced tree water status and stomatal conductance, and reduced leaf osmotic potential and leaf temperature with respect to air temperature. These effects and underlying mechanisms varied across tree water status. Under full irrigation, ANE increased the frequency of very high stomatal conductance (> 0.5 mol m⁻² s⁻¹) at no- to mild- water stress levels (stem water potential, ᴪstem > -1.0 MPa), reducing leaf temperature. In full irrigated trees experiencing short-term stomatal closure, these responses resulted in improved intrinsic water use efficiency, reflecting reduced non-stomatal limitations to photosynthesis. Under deficit irrigation, ANE delayed stomatal closure below 0.37 mol m⁻² s⁻¹ mainly through osmotic adjustment, thereby sustaining gas exchange and postponing the onset of moderate stress (ᴪstem < -1.2 MPa). Collectively, our findings identify a critical ᴪstem range (-1.0 to -1.4 MPa) as a window of maximum ANE efficacy. While these effects did notdirectly increase yield, they promoted slightly heavier kernels. Overall, ANE’s ability to mitigate stress through environmentally sustainable means positions it as a management tool for maintain productivity and enhance orchard resilience under reduced water availability and erratic weather conditions.

  PublisherDOI

• The TreeChill model: A new framework for predicting the impact of erratic winter weather on trees

  Agricultural and Forest Meteorology · 2025-05-27 · 1 citations

  articleSenior authorCorresponding
  PublisherDOI

• Tree water stress influences the biostimulant Ascophyllum nodosum efficacy and mode of action in mature almonds

  SSRN Electronic Journal · 2025-01-01

  preprintOpen accessSenior author
  PublisherDOI

• Le Lignon. A silent restoration

  Digital Access to Libraries (Université catholique de Louvain (UCL), l'Université de Namur (UNamur) and the Université Saint-Louis (USL-B)) · 2025-01-01

  article1st authorCorresponding
  Publisher

• In a nutshell: pistachio genome and kernel development

  New Phytologist · 2025-03-19 · 6 citations

  articleOpen access

  Pistachio is a sustainable nut crop with exceptional climate resilience and nutritional value. However, the molecular processes underlying pistachio nut development and nutritional traits are largely unknown, compounded by limited genomic and molecular resources. To advance pistachios as a future food source and a model system for hard-shelled fruits, we generated a chromosome-scale reference genome of the most widely grown pistachio cultivar (Pistacia vera 'Kerman') and a spatiotemporal study of nut development. We integrated tissue-level physiological data from thousands of nuts over three growing seasons with transcriptomic data encompassing 14 developmental time points of the hull, shell, and kernel to assemble gene modules associated with physiological changes. Our study defined four distinct stages of pistachio nut growth and maturation. We then focused on the kernel to identify transcriptional and metabolic changes in molecular pathways governing nutritional quality, such as the accumulation of unsaturated fatty acids, which are vital for shelf life and dietary value. These findings revealed key candidate conserved regulatory genes, such as PvAP2-WRI1 and PvNFYB-LEC1, likely involved in oil accumulation in kernels. This work yields new knowledge and resources that will inform other woody crops and facilitate further improvement of pistachio as a globally significant, sustainable, and nutritious crop.

  PublisherOA PDFDOI

• Key molecular and cellular events of table olive fruit abscission zone formation during natural maturation and after ethephon treatment

  bioRxiv (Cold Spring Harbor Laboratory) · 2025-11-12

  preprintOpen access

  Abstract Abscission zones are specialized cell layers that enable organ detachment, yet their morphology and regulation vary among species. Olive ( Olea europaea ), a non-climacteric fruit, requires high concentrations of ethylene-releasing compounds to reduce fruit removal force (FRF) for mechanical harvest. To elucidate mechanisms of fruit abscission zone (FAZ) development in olive, we integrated physiological, transcriptomic, and cellular analyses during natural maturation and after ethephon treatment. Olive fruits emitted low ethylene at color transition, coinciding with declining FRF, and application of 1500 ppm ethephon reduced FRF after one week. Transcriptome analyses of FAZ tissues, using a mesocarp-subtraction strategy to isolate FAZ-specific responses, identified 733 FAZ-specific genes shared between natural maturation and ethephon treatments, including genes of β-1,3-glucanases, pectate lyases, and the phenylpropanoid pathway. Microscopy revealed lignification and alkalization of FAZ, accompanied by reduced low-methylesterified homogalacturonan and non-fucosylated xyloglucan. Increased glucanase activity and reduction in plasmodesmata callose likely facilitate cellular communication during abscission. Further, this study provides the first evidence of FAZ alkalization and implicates transporter upregulation in pH regulation preceding abscission. Our findings advance understanding of abscission biology in non-climacteric fruits and delineate conserved features of FAZ development. Summary Statement Integrated physiological, transcriptomic, and cellular analyses reveal that fruit abscission zone development in olive involves lignification, alkalization, and coordinated cell wall remodeling, identifying β-1,3-glucanases, pH-regulating transporters, and pectate lyases that facilitate cell separation in a non-climacteric fruit.

  PublisherDOI

• The Treechill Model: A New Framework for Predicting the Impact of Erratic Winter Weather on Trees

  SSRN Electronic Journal · 2025-01-01

  preprintOpen accessSenior author
  PublisherDOI

• Evolving topological colour landscape unravels the final stages of pistachio nut development and the incidence of blank nuts

  Journal of The Royal Society Interface · 2025-09-01

  articleOpen access

  Pistachio is a major nut crop worldwide; however, there is a lack of standardized non-destructive methods to effectively evaluate maturity and kernel filling for improved management and harvest timing. This study presents an image-based approach to determine pistachio nut maturation and blank kernel incidence by analysing the surface colour patterns of individual nuts at three time points during late development. We identified eight major hull colours to represent the full colour spectrum and applied principal component analysis to divide each nut into seven spatial sections. Within each section, we constructed eight colour-based feature variables (covariates) and associated them with a binary response variable indicating kernel presence or absence. We explored the specific response-covariate relationships at each developmental time point using a data-driven method called categorical exploratory data analysis, which identified key first-order and second-order feature-categories that link hull colour patterns with kernel status. These relationships were visualized using block-structured heatmaps, revealing consistent distinctions between filled and blank nuts. Based on these findings, we developed an algorithm with two main functions: (i) identifying a nut's growth stage from its image for optimal harvest timing and (ii) estimating blank nut incidence for quality assessment and economic decision-making.

  PublisherDOI

• Pistachio

  Elsevier eBooks · 2025-10-17 · 1 citations

  book-chapter1st authorCorresponding
  PublisherDOI

Frequent coauthors

• Tiziano Caruso

  31 shared

• Francesco Paolo Marra

  University of Palermo

  31 shared

• Louise Ferguson

  University of California, Davis

  22 shared

• Alessio Scalisi

  15 shared

• Riccardo Lo Bianco

  University of Palermo

  11 shared

• Paula Guzmán‐Delgado

  10 shared

• Filipa Grilo

  University of California, Davis

  8 shared

• Jaclyn A. Adaskaveg

  Plant (United States)

  7 shared

Awards & honors

• Salas wins thousands for almond research from Miller award (…
• Pokhrel’s passion for pistachio earns FFAR Rockey Fellowship…
• Marino appointed UC Presidential Chair for tree nuts (2022)