From 7 to 9 July 2026, the CITRUSBUSTERS team’s work on volatile biomarkers of citrus disease was presented at the Society for Experimental Biology (SEB) Annual Conference in Florence, Italy. This year’s theme was Resilience.

The oral presentation was delivered by Valentina Lazazzara, a researcher at the Institute for Sustainable Plant Protection of the National Research Council of Italy (CNR-IPSP). Titled “Volatile and biomarkers for early detection of Citrus Black Spot and Citrus Greening Disease in Citrus sinensis”, it summarises a year of work carried out under Work Package 1 (WP1) of CITRUSBUSTERS, in collaboration with the Centro de Citricultura Sylvio Moreira – Instituto Agronômico (CCSM-IAC) in Brazil.

Reading disease in the air

Plants under stress release different mixtures of chemicals into the air than healthy plants do. These volatile organic compounds (VOCs) are part of the plant’s defence system and its way of signalling to its neighbours. Profiling them offers a promising, non-destructive route to detecting disease before symptoms appear.

The team analysed the volatile signatures of two of the world’s most damaging citrus diseases: Citrus Black Spot, caused by the fungus Phyllosticta citricarpa, and Citrus Greening, also known as Huanglongbing (HLB), caused by the bacterium Candidatus Liberibacter asiaticus.

For the fungus, VOCs emitted by P. citricarpa cultures were characterised using SPME/GC-MS analysis. The result was a specific volatile fingerprint made of alcohols, ketones, carboxylic acids, esters and cyclic hydrocarbons. For HLB, the team analysed VOC emissions from Citrus sinensis cv. ‘Valencia’ plants infected with Candidatus Liberibacter asiaticus, both under greenhouse conditions and in Brazilian orchards. In both settings, infection significantly modified the plant’s volatile blend. Monoterpenes, alkanes, alkenes and ketones showed consistent quantitative shifts that cleanly distinguished healthy plants from infected ones.

Detection before the damage

The findings confirm that HLB triggers a deep metabolic reconfiguration in the plant, reaching into the volatile-mediated signalling pathways involved in stress response and defence activation. Ongoing metabolomic analyses will integrate volatile and non-volatile signals to sharpen the diagnostic picture and support future management strategies in the citrus sector. For growers and researchers, the practical implication is direct. Volatilomics profiling now looks like a robust, non-destructive way of identifying early biomarkers of citrus infection, well before symptoms make the disease visible to the human eye.

One more step towards catching citrus disease at the molecular level, before it reaches the leaves.

Contact: Valentina Lazazzara (CNR-IPSP), valentina.lazazzara@cnr.it