Gianfranco Romanazzi

Short hypobaric treatments potentiate the effect of chitosan in reducing storage decay of sweet cherries

The effectiveness of chitosan and short hypobaric treatments, alone or in combination, to control storage decay of sweet cherries, was investigated over 2 years. In single treatments, chitosan was applied by postharvest dipping or preharvest spraying at 0.1, 0.5, and 1.0% concentrations; hypobaric treatments at 0.50 and 0.25 atm were applied for 4 h. In combined treatments, sweet cherries were dipped in 1.0% chitosan and then exposed to 0.50 and 0.25 atm, or sprayed with chitosan (0.1, 0.5, and 1.0%) 7 days before harvest and exposed to 0.50 atm soon after harvest. Untreated sweet cherries kept at normal pressure (near 1.00 atm) were used as controls. Rot incidence was evaluated after 14 days storage at 0±1 °C, followed by a 7 day shelf life. In both years, chitosan and hypobaric treatments applied alone significantly reduced brown rot, grey mould, and total rots, the latter also including blue mould, Alternaria, Rhizopus and green rots. A combined treatment with 1.0% chitosan and 0.50 atm was the best in controlling decay, showing in the first year, a synergistic effect in the reduction of brown rot and total rots. The results indicate that the combination of hypobaric and chitosan treatments is a valid strategy for increasing the effectiveness of the treatments in controlling postharvest decay of sweet cherries.

Preharvest Chitosan and Postharvest UV Irradiation Treatments Suppress Gray Mold of Table Grapes

The effectiveness of chitosan treatment of table grapes, alone or in combination with ultraviolet-C (UV-C) radiation, to control postharvest gray mold caused by Botrytis cinerea, was determined in California, United States. The influence of these treatments on catechin and resveratrol contents and chitinase activity in grape berry skins also was assessed. Clusters of cvs. Thompson Seedless, Autumn Black, and Emperor were sprayed in the vineyard with 1% chitosan, then harvested daily for 5 days. Promptly after harvest, they were inoculated with B. cinerea. Decay incidence and disease severity were significantly reduced by chitosan, which was most effective on berries harvested 1 or 2 days after treatment. In another experiment, grape berries were sprayed in the vineyard with chitosan, harvested 2 days later, irradiated for 5 min with UV-C (0.36 J/cm2), and inoculated with B. cinerea 2 days later. Combined chitosan and UV-C treatments applied to cv. Autumn Black or selection B36-55 were synergistic in reducing gray mold incidence and severity compared with either treatment alone. Preharvest chitosan treatment increased neither concentration of catechin or resveratrol nor activity of chitinase in berry skin. Conversely, UV-C irradiation, alone or combined with chitosan treatment, induced catechin in cv. Autumn Black berries and trans-resveratrol in both cv. Autumn Black and selection B36-55.

Effect of short hypobaric treatments on postharvest rots of sweet cherries, strawberries and table grapes

The effectiveness of short hypobaric treatments against postharvest rots was investigated by exposing sweet cherries, strawberries and table grapes to sub-atmospheric pressures (0.25, 0.50, and 0.75 atm) for different times (from 1 to 24 h). Postharvest rots of sweet cherries and strawberries arose from natural infections, whereas small table grape bunches and artificially wounded single berries were inoculated with Botrytis cinerea after hypobaric treatment. Sweet cherries exposed to 0.50 atm for 4 h had the lowest incidence of gray mould, brown rot and total rots, while a 1 h treatment was not effective. On strawberries, the greatest reductions of gray mould and Rhizopus rot were observed on fruits treated for 4 h at 0.25 and 0.50 atm, respectively. On table grape bunches treatment with 0.25 atm applied for 24 h significantly reduced the incidence of gray mould. In experiments performed with artificially wounded single table grape berries exposed to 0.50 atm for 24 h and then inoculated, the percentage of infected fruits and the diameter of the lesions were significantly reduced, in comparison with the controls. As a sub-atmospheric pressure of 0.25 atm did not affect radial growth of B. cinerea and Monilinia laxa, induced resistance was likely to be responsible for the observed reduction in decay.

Effect of Chitosan Dissolved in Different Acids on Its Ability to Control Postharvest Gray Mold of Table Grape

Chitosan is a natural biopolymer that must be dissolved in an acid solution to activate its antimicrobial and eliciting properties. Among 15 acids tested, chitosan dissolved in 1% solutions of acetic, L-ascorbic, formic, L-glutamic, hydrochloric, lactic, maleic, malic, phosphorous, and succinic acid. To control gray mold, table grape berries were immersed for 10 s in these chitosan solutions that had been adjusted to pH 5.6. The reduction in decay among single berries of several cultivars (Thompson Seedless, Autumn Seedless, and grape selection B36-55) inoculated with Botrytis cinerea at 1 x 10(5) conidia/ml before or after immersion in chitosan acetate or formate, followed by storage at 15 degrees C for 10 days, was approximately 70%. The acids alone at pH 5.6 did not control gray mold. Decay among clusters of two cultivars (Thompson Seedless and Crimson Seedless) inoculated before treatment was reduced approximately 60% after immersion in chitosan lactate or chitosan acetate followed by storage for 60 days at 0.5 degrees C. The viscosity of solutions was 1.9 centipoises (cp) (ascorbate) to 306.4 cp (maleicate) and the thickness of chitosan coating on berries was 4.4 microm (acetate) to 15.4 microm (ascorbate), neither of which was correlated with solution effectiveness. Chitosan acetate was the most effective treatment which effectively reduced gray mold at cold and ambient storage temperatures, decreased CO2 and O2 exchange, and did not injure the grape berries.

Shelf life extension of fresh fruit and vegetables by chitosan treatment

ABSTRACT Among alternatives that are currently under investigation to replace the use of synthetic fungicides to control postharvest diseases in fresh produce and to extend their shelf life, chitosan application has shown promising disease control, at both preharvest and postharvest stages. Chitosan shows a dual mode of action, on the pathogen and on the plant, as it reduces the growth of decay-causing fungi and foodborne pathogens and induces resistance responses in the host tissues. Chitosan coating forms a semipermeable film on the surface of fruit and vegetables, thereby delaying the rate of respiration, decreasing weight loss, maintaining the overall quality, and prolonging the shelf life. Moreover, the coating can provide a substrate for incorporation of other functional food additives, such as minerals, vitamins, or other drugs or nutraceutical compounds that can be used to enhance the beneficial properties of fresh commodities, or in some cases the antimicrobial activity of chitosan. Chitosan coating has been approved as GRAS substance by USFDA, and its application is safe for the consumer and the environment. This review summarizes the most relevant and recent knowledge in the application of chitosan in postharvest disease control and maintenance of overall fruit and vegetable quality during postharvest storage.

Expression of Defense Genes in Strawberry Fruits Treated with Different Resistance Inducers.

The expression of 18 defense genes in strawberry fruit treated with elicitors: chitosan, BTH, and COA, at 0.5, 6, 24, and 48 h post-treatment was analyzed. The genes were up-regulated differentially, according to the elicitor. Chitosan and COA treatments promoted the expression of key phenylpropanoid pathway genes, for synthesis of lignin and flavonoids; only those associated with flavonoid metabolism were up-regulated by BTH. The calcium-dependent protein kinase, endo-β 1,4-glucanase, ascorbate peroxidase, and glutathione-S-transferase genes were up-regulated by BTH. The K+ channel, polygalacturonase, polygalacturonase-inhibiting protein, and β-1,3-glucanase, increased in response to all tested elicitors. The enzyme activities of phenylalanine ammonia lyase, β-1,3-glucanase, Chitinase, and guaiacol peroxidase supported the gene expression results. Similarity of gene expression was >72% between chitosan and COA treatments, while BTH showed lower similarity (38%) with the other elicitors. This study suggests the relationship between the composition of the elicitors and a specific pattern of induced defense genes.

Seed treatments to control seedborne fungal pathogens of vegetable crops

Vegetable crops are frequently infected by fungal pathogens, which can include seedborne fungi. In such cases, the pathogen is already present within or on the seed surface, and can thus cause seed rot and seedling damping-off. Treatment of vegetable seeds has been shown to prevent plant disease epidemics caused by seedborne fungal pathogens. Furthermore, seed treatments can be useful in reducing the amounts of pesticides required to manage a disease, because effective seed treatments can eliminate the need for foliar application of fungicides later in the season. Although the application of fungicides is almost always effective, their non-target environmental impact and the development of pathogen resistance have led to the search for alternative methods, especially in the past few years. Physical treatments that have already been used in the past and treatments with biopesticides, such as plant extracts, natural compounds and biocontrol agents, have proved to be effective in controlling seedborne pathogens. These have been applied alone or in combination, and they are widely used owing to their broad spectrum in terms of disease control and production yield. In this review, the effectiveness of different seed treatments against the main seedborne pathogens of some important vegetable crops is critically discussed.

Genetic variability of the stolbur phytoplasma vmp1 gene in grapevines, bindweeds and vegetables.

Aim:  Evaluation of the genetic variability of stolbur phytoplasma infecting grapevines, bindweeds and vegetables, collected in different central and southern Italian regions.

Seasonal Variation of Defense-Related Gene Expression in Leaves from Bois noir Affected and Recovered Grapevines

Although Bois noir is one of the main phytoplasma diseases of grapevine, the gene expression and enzyme activities that underlie physiological changes occurring in symptomatic and recovered (with spontaneous or induced symptom remission) plants are mostly unknown. Bois noir symptomatic leaves (September 2006, 2007) and symptomless leaves from infected symptomatic plants (September 2007) of Sangiovese (moderately susceptible) and Chardonnay (highly susceptible) cultivars were collected. Moreover, leaves from infected symptomless plants of both cultivars were harvested in June 2007. Leaves from recovered plants were also collected in the same periods. In recovered plants of both cultivars, class III chitinase and almost every time phenylalanine ammonia-lyase and chalcone synthase expression were increased for all collection periods. In symptomatic leaves of both cultivars, the expressions of the same genes were up-regulated and also those of β-1,3-glucanase and flavanone 3-hydroxylase. The activities of chitinase, phenylalanine ammonia-lyase, β-1,3-glucanase, and superoxide dismutase generally correlated with gene expression. For the moderately susceptible Sangiovese, the defense genes were generally up-regulated in both symptomatic and symptomless leaves (for all collection periods). This behavior was not observed in the highly susceptible Chardonnay, in which changes in gene expression were linked to evident symptom display. Therefore, the physiological response of the plants to this pathogen infection appear to be the reason for the resistance of the cultivar to the disease.

Genetic Variability of Stolbur Phytoplasma in Hyalesthes obsoletus (Hemiptera: Cixiidae) and its Main Host Plants in Vineyard Agroecosystems

ABSTRACT Bois noir is an economically important grapevine yellows that is induced by ‘Candidatus Phytoplasma solani’ and principally vectored by the planthopper Hyalesthes obsoletus Signoret (Hemiptera: Cixiidae). This study explores the ‘Ca. P. solani’ genetic variability associated to the nettle—H. obsoletus and bindweed—H. obsoletus systems in vineyard agroecosystems of the central-eastern Italy. Molecular characterization of ‘Ca. P. solani’ isolates was carried out using polymerase chain reaction/ restriction fragment length polymorphism to investigate the nonribosomal vmp1 gene. Seven phytoplasma vmp-types were detected among the host plants- and insect-associated field-collected samples. The vmp1 gene showed the highest polymorphism in the bindweed—H. obsoletus system, according to restriction fragment length polymorphism analysis, which is in agreement with nucleotide sequence analysis. Five vmp-types were associated with H. obsoletus from bindweed, of which one was solely restricted to planthoppers, with one genotype also in planthoppers from nettle. Type V12 was the most prevalent in both planthoppers and bindweed. H. obsoletus from nettle harbored three vmp-types, of which V3 was predominant. V3 was the only type detected for nettle. Our data demonstrate that planthoppers might have acquired some ‘Ca. P. solani’ profiles from other plant hosts before landing on nettle or bindweed. Overall, the different vmp1 gene rearrangements observed in these two plant hosts-H. obsoletus systems might represent different adaptations of the pathogen to the two host plants. Molecular information about the complex of vmp-types provides useful data for better understanding of Bois noir epidemiology in vineyard agroecosystem.