Valentina Picchi

Leaf level early assessment of ozone injuries by passive fluorescence and photochemical reflectance index

Excess energy dissipation pathways (heat and fluorescence) were monitored, at leaf level as indicators of plant physiological status, with field spectroscopy techniques on poplar clones subjected to ozone fumigation. Measurements of spectral radiance emerging from a leaf provide a fast, non‐destructive method for the assessment of excess energy dissipation: xanthophyll‐related heat dissipation was estimated with the photochemical reflectance index (PRI) calculated from a traditional field spectrometer, and steady‐state fluorescence (Fs) under natural illumination conditions was estimated by exploiting a variation of the Fraunhofer line‐depth principle, where the radiance collected with very high resolution spectrometers (FWHM = 0.13 nm) was spectrally modelled. Both remotely‐sensed dissipation pathways responded to fumigation. During a 26‐day fumigation experiment, four diurnal cycles of spectral measurements were collected in parallel to meteorological and key physiological variables (active fluorescence, net photosynthesis) and leaf sample collection for pigment extraction. We outline evidence of a link between the remotely‐sensed Fs and PRI and leaf physiological status. These results open up new possibilities for assessment of plant stress by means of hyperspectral remote sensing.

Nutritional Traits of Bean (Phaseolus vulgaris) Seeds from Plants Chronically Exposed to Ozone Pollution

The effect of chronic exposure to ozone pollution on nutritional traits of bean ( Phaseolus vulgaris L. cv. Borlotto Nano Lingua di Fuoco) seeds from plants grown in filtered and nonfiltered open-top chambers (OTCs) has been investigated. Results showed that, among seed macronutrients, ozone significantly raised total lipids, crude proteins, and dietary fiber and slightly decreased total free amino acid content, although with a significant reduction of asparagine, lysine, valine, methionine, and glycine, compensated by a conspicuous augmentation of ornithine and tryptophan. Phytosterol analysis showed a marked increase of beta-sitosterol, stigmasterol, and campesterol in seeds collected from nonfiltered OTCs. With regard to secondary metabolites, ozone exposure induced a slight increase of total polyphenol content, although causing a significant reduction of some flavonols (aglycone kaempferol and its 3-glucoside derivative) and hydroxycinnamates (caffeic, p-coumaric, and sinapic acids). Total anthocyanins decreased significantly, too. Nevertheless, ozone-exposed seeds showed higher antioxidant activity, with higher Trolox equivalent antioxidant capacity (TEAC) values than those measured in seeds collected from filtered air.

Nitrogen Status Assessment for Variable Rate Fertilization in Maize through Hyperspectral Imagery

This paper presents a method for mapping the nitrogen (N) status in a maize field using hyperspectral remote sensing imagery. An airborne survey was conducted with an AISA Eagle hyperspectral sensor over an experimental farm where maize (Zea mays L.) was grown with two N fertilization levels (0 and 100 kg N ha−1) in four replicates. Leaf and canopy field data were collected during the flight. The nitrogen (N) status has been estimated in this work based on the Nitrogen Nutrition Index (NNI), defined as the ratio between the leaf actual N concentration (%Na) of the crop and the minimum N content required for the maximum biomass production (critical N concentration (%Nc)) calculated through the dry mass at the time of the flight (Wflight). The inputs required to calculate the NNI (i.e., %Na and Wflight) have been estimated through regression analyses between field data and remotely sensed vegetation indices. MCARI/MTVI2 (Modified Chlorophyll Absorption Ratio Index/Modified Triangular Vegetation Index 2) showed the best performances in estimating the %Na (R2 = 0.59) and MTVI2 in estimating the Wflight (R2 = 0.80). The %Na and the Wflight were then mapped and used to compute the NNI map over the entire field. The NNI map agreed with the NNI estimated using field data through traditional destructive measurements (R2 = 0.70) confirming the potential of using remotely sensed indices to assess the crop N condition. Finally, a method to derive a pixel based variable rate N fertilization map was proposed as the difference between the actual N content and the optimal N content. We think that the proposed operational methodology is promising for precision farming since it represents an innovative attempt to derive a variable rate N fertilization map based on the actual crop N status from an aerial hyperspectral image.

Variations in the phytochemical contents and antioxidant capacity of organically and conventionally grown Italian cauliflower (Brassica oleracea L. subsp. botrytis): results from a three-year field study.

A three-year field study (2009-2011) was performed to evaluate phytochemicals and antioxidant capacities of two genotypes (HF1 Emeraude and the local variety, Velox) of green cauliflower grown under organic and conventional management. The conventional system increased yield, but had little effect on the dry matter, whereas the organic system increased the soluble solids. Phytochemicals and antioxidant capacity showed significant year-to-year variability. During the third year, the scarce rainfall determined a significant increase of total glucosinolates and a general decrease of antioxidants in all samples. Interestingly, in the same year organic plants were less affected by the unfavorable climatic conditions, as they increased ascorbic acid, polyphenols, and carotenoids with respect to conventional ones. The overall results for the three years showed that the two genotypes responded differently. Compared to the conventional system, Velox showed 24, 21, 13, 48, and 44% higher content of ascorbic acid, polyphenols, carotenoids, volatiles, and antioxidant capacity, respectively. In contrast, no significant increase in the phytochemicals or the antioxidant potential was found in organic Emeraude, with the exception of total volatiles (+41%). These findings suggest that organic cultivation may be highly effective for particular cauliflower genotypes.

Inhibition of ochratoxin A production in Aspergillus carbonarius by hydroxycinnamic acids from grapes

Hydroxycinnamic acids (HCAs), phenolic components of wine, are known to have antimicrobial properties. Aspergillus carbonarius is one of the most important ochratoxin A (OTA) producing fungi in wine. Strategies for the control and prevention of A. carbonarius contamination are important for the maintenance of wine safety. This study sought to determine the potential of HCAs, such as caffeic, p-coumaric and ferulic acids, as antifungal natural compounds for the control of A. carbonarius growth and OTA production. The HCAs were tested at the increasing concentrations of 0.30, 0.65 and 1.10 mg/ml in minimal medium (MM) and grape juice. Germination of conidia was not affected in neither of the two media in presence of HCAs. At all the concentrations tested, OTA biosynthesis in MM was reduced and the dose effect was more evident for p-coumaric and ferulic acids; in grape juice the reduction trend was confirmed, and ferulic acid showed the highest inhibitory effect. Moreover, the expression level of genes encod...

Phytochemical Concentrations and Antioxidant Capacity of Grapes Treated with Low Copper Formulations against Downy Mildew

A two-year study was conducted in an organic vineyard to evaluate the phytochemical concentrations and antioxidant capacity of grapes treated with low copper for downy mildew control compared to grapes that were untreated or treated with a standard fungicide. The metabolic profile, antioxidant capacity, and downy mildew incidence and severity were assessed. The maturity of grapes was an important factor in determining the potential risk for the spread of fungal disease, as suggested by principle components analysis (PCA), which showed a positive relationship between tartaric acid concentration and both incidence and severity of downy mildew disease. Polyphenols and thiols were more abundant in berries with less disease. The thiols were highly correlated with the antioxidant capacity, indicating an important role of these metabolites in determining the antioxidant potential of grape berries. Moreover, both the antioxidant indexes and thiols in the PCA were plotted opposite the disease severity and incidence, suggesting that higher antioxidant potential may be responsible for an increased capacity of grapes to counteract the disease. Results showed that low-copper formulations could control grape downy mildew in the field with a similar efficacy to the standard reference fungicide, without affecting the phytochemical profile and the antioxidant potential of grapes. Low-copper formulations may be thus considered alternatives for organic agriculture that minimize costs and copper accumulation in the soil, thus ensuring grape quality in a sustainable crop management system.