Contamination of microgreens by Salmonella enterica and Escherichia coli is influenced by selection breeding in chicory (Cichorium intybus L.)

The aim of this study was to assess whether selection breeding in chicory (Cichorium intybus L.) led changes in the susceptibility to Salmonella enterica and Escherichia coli contamination and whether the anatomical traits of the leaves are involved in the possible changes. Five chicory genotypes subjected to different intensities of selection were compared at the microgreen stage. Bacterial retention was evaluated after leaf incubation for 1.5 h on the surface of the bacterial suspension, followed by rinsing, grinding, plating on selective media, and colony forming unit (CFU) counting. The density of stomata and trichomes, total stomatal length and width, stomatal pit width, surface roughness and sharpness were evaluated. The intensively selected genotype (Witloof) was signifcantly more prone to contamination (2.9±0.3 lg CFU/cm2 ) as the average of the two bacterial types than the wild accession (Wild; 2.3±0.4 lg CFU/cm2 ) and the moderately selected genotypes (two leaf chicories, Catalogna type, and root chicory ‘Magdeburg’; on average, 1.9±0.3 lg CFU/cm2 ). Witloof microgreens also showed larger stomata (on average +34% for stoma width and +44% for pit width), which could justify, at least in part, the higher susceptibility to enterobacterial contamination. In fact, when contamination was performed in the dark (closed stomata), the bacterial retention in Witloof was signifcantly reduced in comparison with the opened stomata (–44%) and in Wild (–26%). Differences in retention between Witloof and Wild were still observed after UV treatment. The hierarchical clustering performed by grouping the leaf anatomical features was consistent with the chicory genetic groups. Our results suggest that the domestication process can affect the safety of produce and that the micromorphological traits of the leaves may be involved