Citrus canker, caused by Xanthomonas axonopodis Starr and Garces pv. citri (Hasse) Vauterin et al., is one of the main problems affecting citrus production. In order to obtain resistance to phytopathogenic bacteria, insect genes, coding for antimicrobial proteins, have been used in plant genetic transformation. In this study, transgenic Citrus sinensis (L.) Osb. `Hamlin' plants expressing the antimicrobial insect-derived attacin A gene (attA) were obtained by Agrobacterium tumefaciens (Smith and Towns.) Conn-mediated transformation. Initially, the cDNA clone was used to construct a binary plasmid vector (pCattA 2300). The construction included the native signal peptide (SP) responsible for directing the insect protein to the extracellular space where bacteria is supposed to accumulate in vivo. In order to investigate the native SP effectiveness in a plant model system, onion (Allium cepa L.) epidermal cells were transformed, via biobalistics, using plasmids containing the attA gene with or without SP, fused with the green fluorescent protein gene (pattA 1303 and pSPattA 1303). Fluorescence accumulation surrounding the cells was observed only in tissues transformed with the plasmid containing the gene with SP, indicating the protein secretion to the apoplast. Citrus transformation was confirmed by PCR and Southern blot hybridization analysis in 12 regenerated plants. Transcription of attA gene was detected by Northern blot analysis in all transgenic plants. Eight selected transgenic lines were propagated and inoculated with a 106 cfu/mL suspension of the pathogen X. axonopodis pv. citri. Compared to control (non-transformed plant), seven transgenic lines showed a significant reduction in susceptibility to citrus canker. The results obtained here indicate the potential use of antibacterial proteins to protect citrus from bacterial diseases.

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The aim of this study was to develop and validate an HPLC-DAD method to evaluate the phenolic compounds profile of organic and conventional Pêra-Rio orange juice. The proposed method was validated for 10 flavonoids and 6 phenolic acids. A wide linear range (0.01-223.4μg·g), good accuracy (79.5-129.2%) and precision (CV≤3.8%), low limits of detection (1-22ng·g) and quantification (0.7-7.4μg), and overall ruggedness were attained. Good recovery was achieved for all phenolic compounds after extraction and cleanup. The method was applied to organic and conventional Pêra-Rio orange juices from beginning, middle and end of the 2016 harvest. Flavones rutin, nobiletin and tangeretin, and flavanones hesperidin, narirutin and eriocitrin were identified and quantified in all organic and conventional juices. Identity was confirmed by mass spectrometry. Nineteen non-identified phenolic compounds were quantified based on DAD spectra characteristic of the chemical class: 7 cinnamic acid derivatives, 6 flavanones and 6 flavones. The phenolic compounds profile of Pêra-Rio orange juices changed during the harvest; levels increased in organic orange juices, and decreased or were about the same in conventional orange juices. Phenolic compounds levels were higher in organic (0.5-1143.7mg·100g) than in conventional orange juices (0.5-689.7mg·100g). PCA differentiated organic from conventional FS and NFC juices, and conventional FCOJ from conventional FS and NFC juices, thus differentiating cultivation and processing.

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Total antioxidant activity (TAA), total phenolic compounds (TPC), and physicochemical characteristics of ready-to-drink orange juice and nectar from the most consumed brands available in Brazil were evaluated. TPC ranged from 18.7 to 54.2 mg of gallic acid/100 mL, and TAA varied from 57.88 to 349.32 μmol TEAC/100 mL ready-to-drink orange juice and nectar. The ascorbic acid content was the only physicochemical parameter that showed strong variation among packages and brands. Correlation of TPC with TAA showed that the higher the level of TPC the higher the TAA. Correlation of ascorbic acid content with TAA is higher for ready-to-drink orange juice than nectar. The same was found for the correlation of ascorbic acid content with TPC. The results confirm the contribution of the TPC to TAA.

TPC values increased during ripening for both organic and conventional passion fruit. The same was true for TAA values for conventional passion fruit. For organic passion fruit, however, TAA values were highest at the initial ripening stages. These results suggest that antioxidant compounds exert strong influence on the initial ripening stages for organic passion fruit, when TPC still did not reach its maximum level.

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