From Pathogens to Pathobiomes

Samir Droby, a Senior Research Scientist at the ARO-Volcani Institute and Professor at the Hebrew University of Jerusalem, has been at the forefront of global postharvest pathology for more than thirty-five years, pioneering biological control and fruit microbiome research. In the late 1980s, collaborating with USDA-ARS scientists, Drs. Charles Wilson and Michael Wisniewski in the US, and Dr. Edo Chalutz at the ARO, Volcani Center, Prof. Droby sought sustainable alternatives to chemical fungicides by exploring the protective role of natural microbial communities on fruit surfaces. This initial concept evolved into a major global research field. His work utilized naturally occurring yeasts as biological shields against destructive molds throughout the food supply chain. Droby’s research unraveled biological control mechanisms, establishing the foundation for commercializing unique yeasts, such as Candida oleophila and Metschnikowia fructicola, into bio-fungicides.

By the mid-2000s, despite isolated successes with commercial yeast products, postharvest biocontrol faced significant challenges regarding consistency and industrial adoption. Challenging conventional concepts, Droby and international colleagues co-authored a landmark 2008 review in Postharvest Biology and Technology (PBT) titled “Twenty years of postharvest biocontrol research: Is it time for a new paradigm?“. Accumulating over 1,100 citations, this influential paper argued against using biocontrol merely as a direct replacement for synthetic chemical fungicides. Instead, it steered the scientific community toward a holistic ecological approach, highlighting complex multitrophic interactions within the pathosystem, fundamentally resetting global postharvest biocontrol research priorities.

As high-throughput sequencing technologies progressed, Prof. Droby catalyzed another paradigm shift. In a 2018 PBT feature article, he introduced the fruit surface—the carposphere—as a complex, interconnected microbial network. This shifted focus from single biocontrol strains to comprehensive microbial communities, laying the groundwork for designing custom Synthetic Microbial Communities (SynComs) that provide robust, consistent efficacy and climate-resilient protection. Recently, Prof. Droby challenged decades of academic doctrine by introducing the postharvest pathobiome concept in another PBT opinion article. This work redefined the infection process by revealing a “hidden alliance” where resident helper bacteria form an inter-kingdom synergy with fungal pathogens to facilitate host penetration and accelerate decay.

To combat destructive postharvest rots, Prof. Droby recognized scientists first needed to decode the molecular weapons and host cues utilized by pathogens. Supported by BARD-funded projects, his laboratory investigated the tissue-specific mechanics of major postharvest pathogens, including Penicillium digitatum (green mold), Penicillium expansum (blue mold), and Botrytis cinerea (grey mold). They discovered that volatiles emitted from wounded fruit exert a highly specific stimulatory effect promoting P. digitatum infection, enabling the pathogen to exploit host cues. For the broad-host blue mold P. expansum, Droby and collaborators characterized LysM effectors, which are highly expressed during early infection stages to conceal the fungus from the fruit’s immune system.

Central to the international scope of Prof. Droby’s research was funding with the U.S.-Israel Binational Agricultural Research and Development Fund (BARD). Providing crucial funding from an initial 1991 postharvest biocontrol feasibility study, BARD has served as the financial bedrock of his work. Throughout his career, Prof. Droby secured twelve BARD-funded projects (8 as PI) alongside support from other national and global agencies and industry partners. These resources enabled continuous collaborations with American institutions like the USDA-ARS, Virginia Tech, and Cornell University, as well as universities across Asia and Europe. Additionally, BARD funded three international workshops that fostered global scientific collaboration. In return Prof. Droby has contributed to BARD serving for many years on the postharvest panel as well as a term on the Technical Advisory Committee.

Prof. Droby’s leadership has significantly shaped global research priorities. He served as chairperson of the Postharvest Subject Committee for the International Society of Plant Pathology (ISPP) and held key roles within the International Society for Horticultural Science (ISHS. Beyond the laboratory, his career is defined by a steadfast commitment to global mentorship and diversity. While working at the Volcani Institute and holding visiting scientist positions abroad, he trained generations of international students, researchers, and farmers, sharing his knowledge to ensure a safe, sustainable global harvest.

Prof. Droby’s contributions provide a comprehensive roadmap for future research, advocating for a multisystem approach that treats fresh produce as a dynamic microscopic universe. He suggests That future crop loss management must utilize advanced multi-omics tools, such as metagenomics, transcriptomics, and metabolomics, to map real-time microbial dynamics on fruit surfaces. Harnessing carposphere microbiome data alongside AI and machine learning will enable industries to predict decay vulnerabilities during storage and shipping before physical symptoms manifest. Ultimately, this paradigm relies on Integrated Multi-Layered Defenses (IMLD), an innovative strategy combining microbiome modulations via SynCom deployment, physical treatments, and innate host immunity manipulation to ensure global food security.