Endogenous falcarinol-type polyacetylenes in carrots and their putative influence on post-harvest fungal pathogens Mycocentrospora acerina and Botrytis cinerea

Falcarinol-type polyacetylenes are a main group of natural bitter compounds synthesized in carrot taproots and putatively contribute to defence mechanisms against soil-borne fungal pathogens. In this study, we analysed the relationships between the constitutive levels of these secondary metabolites and the extent of root infection with the two main carrot storage fungal pathogens Mycocentrospora acerina (liquorice rot) and Botrytis cinerea (grey mold). Taproots of eight differently colored carrot cultivars exhibiting different levels of the three main falcarinol-type polyacetylenes were inoculated with the two fungi and evaluated for diseased area with a digital image analysis system after 6-weeks incubation in a cold storage facility. After inoculation on cortex tissue and the periderm of taproots, a progressed carrot breeding line and the cultivar Bolero demonstrated the highest tolerance to both M. acerina and B. cinerea, while Blanche and Senta were the most susceptible cultivars. Concentrations of falcarinol-type polyacetylenes were negatively correlated, though not significantly, with M. acerina and B. cinerea disease severity. Nevertheless, our study has provided further insights into the naturally occurring variability for the accumulation of falcarinol-type polyacetylenes in cultivated carrots and their putative contributions to resistance against post-harvest fungal pathogens M. acerina and B. cinerea. To our knowledge, this is the first study about the pathogenicity of B. cinerea after inoculation of different carrot cultivars with known root PA levels.