Evaluation of the postharvest quality of Cagaita fruits (Eugenia dysenterica DC.) coated with chitosan and associated with refrigeration

Cagaita fruits are subject to seasonality and perishability. This work aims to use scanning electron microscopy (SEM) to evaluate the physicochemical characteristics, texture, color and physical structure of cagaita fruits coated with different chitosan concentrations. The fruits were divided as follows: T0 (uncoated fruits), T1 (fruits coated with 1% (v/v) chitosan), T2 (fruits coated with 2% (v/v) chitosan) and T3 (fruits coated with 3% (v/v) chitosan). They were analyzed at 0, 10, 20 and 30 days of storage. Titratable acidity and soluble solids content showed no conservation of fruit characteristics; they showed better results for uncoated fruits, as well as weight loss, vitamin C and peak strain. The color of cagaita fruits confirmed ripening during storage regardless of treatment. Scanning electron microscopy showed that the film solution did not adhere, as desired, to the cell wall of fruits. As the results of fruits coated with 3% pectin were close to control, further studies should be carried out with higher coating percentages so that the fruit quality is maintained during storage.Keywords: Physical structure, film solution, quality, shelf life

Comparative genomics reveals diversity among xanthomonads infecting tomato and pepper

<p>Abstract</p> <p>Background</p> <p>Bacterial spot of tomato and pepper is caused by four <it>Xanthomonas </it>species and is a major plant disease in warm humid climates. The four species are distinct from each other based on physiological and molecular characteristics. The genome sequence of strain 85-10, a member of one of the species, <it>Xanthomonas euvesicatoria </it>(<it>Xcv</it>) has been previously reported. To determine the relationship of the four species at the genome level and to investigate the molecular basis of their virulence and differing host ranges, draft genomic sequences of members of the other three species were determined and compared to strain 85-10.</p> <p>Results</p> <p>We sequenced the genomes of <it>X. vesicatoria </it>(<it>Xv</it>) strain 1111 (ATCC 35937), <it>X. perforans </it>(<it>Xp</it>) strain 91-118 and <it>X. gardneri </it>(<it>Xg</it>) strain 101 (ATCC 19865). The genomes were compared with each other and with the previously sequenced <it>Xcv </it>strain 85-10. In addition, the molecular features were predicted that may be required for pathogenicity including the type III secretion apparatus, type III effectors, other secretion systems, quorum sensing systems, adhesins, extracellular polysaccharide, and lipopolysaccharide determinants. Several novel type III effectors from <it>Xg </it>strain 101 and <it>Xv </it>strain 1111 genomes were computationally identified and their translocation was validated using a reporter gene assay. A homolog to Ax21, the elicitor of XA21-mediated resistance in rice, and a functional Ax21 sulfation system were identified in <it>Xcv</it>. Genes encoding proteins with functions mediated by type II and type IV secretion systems have also been compared, including enzymes involved in cell wall deconstruction, as contributors to pathogenicity.</p> <p>Conclusions</p> <p>Comparative genomic analyses revealed considerable diversity among bacterial spot pathogens, providing new insights into differences and similarities that may explain the diverse nature of these strains. Genes specific to pepper pathogens, such as the O-antigen of the lipopolysaccharide cluster, and genes unique to individual strains, such as novel type III effectors and bacteriocin genes, have been identified providing new clues for our understanding of pathogen virulence, aggressiveness, and host preference. These analyses will aid in efforts towards breeding for broad and durable resistance in economically important tomato and pepper cultivars.</p