Proximal optical sensors (POSs) are effective devices for monitoring the development of crops and the nitrogen (N) status of plants. POSs are both useful and necessary in facilitating the reduction of N losses into the environment and in attaining higher nitrogen use efficiency (NUE). To date, no comparison of these instruments has been made on quinoa. A field experiment conducted in Tuscany, Italy, with different POSs, has assessed the development of quinoa with respect to N status. Three sets of POSs were used (SPAD-502, GreenSeeker, and Canopeo App.) to monitor quinoa development and growth under different types of fertilizers (digestate and urea) and levels of N fertilization (100, 50, and 0 kg N ha−1). The present findings showed that in-season predictions of crop biomass at harvest by SPAD-502 and GreenSeeker optical sensors were successful in terms of the coefficient of determination (R2 = 0.68 and 0.82, respectively) and statistical significance (p < 0.05), while the Canopeo App. was suitable for monitoring the plant´s canopy expansion and senescence. The relative error (RE%) showed a remarkably high performance between observed and predicted values, 5.80% and 4.12% for GreenSeeker and SPAD-502, respectively. Overall, the POSs were effective devices for monitoring quinoa development during the growing season and for predicting dry biomass at harvest. However, abiotic stresses (e.g., heat-stress conditions at flowering) were shown to reduce POSs’ accuracy when estimating seed yields at harvest, and this problem will likely be overcome by advancing the sowing date.

No abstract

Understanding the relation between the susceptibility of different leafy greens to human pathogen contamination and leaf traits can contribute to increase the food safety of the fresh vegetable industry. The aim of this research was to evaluate the susceptibility to E. coli ATCC 35218 attachment in 30 accessions of baby leaves, and to identify leaf traits potentially involved in the contamination. The accessions were surface inoculated with a bacterial suspension containing 1 × 107 cells/mL and the attachment was measured 1.5 h after inoculation. Significant differences in attachment were detected between the accessions for p ≤ 0.05. The three most and the three least susceptible accessions were selected and characterized for leaf micro-morphological traits (stomata density and size, surface roughness) and water content. Scanning electron microscopy was used to analyse the stomatal parameters. Roughness was measured by an innovative portable 3D digital microscope. No significant correlation between the attachment of E. coli ATCC 35218 and stomatal parameters was detected, while the attachment was positively correlated with roughness and water content. The E. coli ATCC 35218 population in surface-inoculated leaves was also measured after a UV treatment, which was found to be less effective in reducing bacterial contamination in the rougher leaves. This result suggested that roughness offers UV protection, further highlighting its impact on the microbiological safety of baby leafy greens.

Objectives 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. Materials and Methods 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 CFU counting. The density of stomata and trichomes, total stomatal length and width, stomatal pit width, surface roughness and sharpness were evaluated. Results The intensively selected genotype (Witloof) was significantly more prone to contamination ((2.9±0.3) lg CFU/cm 2) as the average of the two bacteril types than the wild accession (Wild) ((2.3±0.4) lg CFU/cm 2) and the moderately selected genotypes (two leaf chicories, Catalogna type, and root chicory ‘Magdeburg’) (on average, (1.9±0.3) lg CFU/cm 2). 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 enterobacteria contamination. In fact, when contamination was performed in the dark (closed stomata), the bacterial retention in Witloof was significantly 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. Conclusions Our results suggest that the domestication process can affect the safety of produce and that the micromorphological traits of the leaves may be involved.