Volatile organic compound profiles in sudden death syndrome disease

ESPAÑOL, LAUREANO A.; RAMOS, ROCÍO S.; SPAMPINATO, CLAUDIA P.

Mendoza

Congreso; LVIII Reunión Anual SAIB; 2022

Fusarium tucumaniae (Ft) and Fusarium crassistipitatum (Fc) are fungus species that cause sudden death syndrome (SDS) in soybean crops in Argentina. These necrotrophic fungi infect root plants andgenerate foliar symptoms. Soil microorganisms and plant interaction is mediated by a wide range of chemical compounds. Published reports demonstrate that emitted volatile organic compounds (VOCs)can modulate plant growth and fungi virulence and that VOCs profiles can be altered by fungal growth conditions. In this work, we identified and compared VOC emission from Ft and Fc- infected soil andsoybean roots as well as Ft and Fc grown in rich culture medium. For soybean infection, inoculum was prepared by culturing Ft and Fc strains on potato dextrose agar (PDA) in plastic Petri dishes for 1 week at 25 °C in the dark. Five agar plugs (6 mm diameter) with mycelium were added to autoclaved sorghum grains. The flask was incubated at 25 °C in the dark for 2 weeks. A nursery substrate was plugged in pots and a layer of infected sorghum were distributed in experimental pots and covered with the same substrate. Control pots contained non-inoculated sorghum grains. Five seeds of a susceptible SDSgenotype were placed in each pot and covered with substrate. At 15 days after infection, VOCs from tap root areas contacting the sorghum seed sand rhizosphere soil were identified by head space solid phase microextraction (HS-SPME) coupled to gas chromatography-mass spectrometer (GC-MS). Toluene was used as an internal standard. In addition, VOCs from pure fungal cultures were analysed. PDA alone was used as a control sample. Identified VOCs were classified into the following biochemical groups: acids, terpenes, aldehydes, ketones and alcohols. Some of these differ between pathogen growth conditions, but not by any of the fungal pathogens used. More different types of alcohols were found in infected roots than in rhizosphere or in rich culture media. However, among these, 1-octen-3-ol accumulated only inrhizosphere and culture media compared with controls. More different types of terpenes were identified in rich media than in the other two conditions. Contrarily, aldehydes were more abundant in infected rootsand rhizosphere compared with culture media. Among these, increased levels of benzaldehyde and 2-hydroxy benzaldehyde were found in root samples and rhizosphere due to the infection. Taken together,our results suggest that VOC profiles qualitatively and quantitative differ between samples. Identification of differential compounds may improve our understanding of plant-pathogen interaction and suggestthat these chemical signals could be used as new strategies to estimate or control SDS disease severity.