Fiorella Neri

Fungicidal Activity of Plant Volatile Compounds for Controlling Monilinia laxa in Stone Fruit

Nine plant-volatile compounds were tested for their activity against Monilinia laxa, the cause of brown rot in stone fruit. In vitro trials on conidial germination and mycelial growth showed a consistent fungicidal activity of trans-2-hexenal, carvacrol, and citral, whereas trans-cinnamaldehyde, hexanal, (-)-carvone, eugenol, 2-nonanone, and p-anisaldehyde exhibited a progressively lower inhibition. The best inhibitor of conidial germination was trans-2-hexenal (effective dose for 50 and 90% inhibition [ED50 and ED95] = 7.53 and 9.4 μl/liter, respectively; minimal inhibitory concentration [MIC] = 12.3 μl/liter], whereas carvacrol was the best inhibitor of mycelial growth (ED50 and ED95 = 2 and 3.4 μl/liter, respectively; MIC = 6.1 μl/liter). The three most active compounds in in vitro studies also were tested in vivo as postharvest biofumigants. The best control of brown rot was with trans-2-hexenal (efficacy ranging from 46.2 to 80.3%, depending on cultivar), whereas citral and carvacrol resulted in a lower efficacy of 40 and 32.9%, respectively. Fumigation with trans-2-hexenal at concentrations that stopped decay did not cause any visible disorders to plum, whereas it was phytotoxic to apricot, peach, and nectarine and produced off-odors or off-flavors in all species of stone fruit tested.

Activity of natural compounds on Fusarium verticillioides and fumonisin production in stored maize kernels.

The ability of trans-2-hexenal, carvacrol and eugenol to control F. verticillioides was explored in vitro and in artificially infected kernels. The effect of the trans-2-hexenal fumigation on F. verticillioides control, fumonisin production and kernel germination was also investigated in naturally infected kernels. Trans-2-hexenal, carvacrol and eugenol vapour showed fungicidal activity against F. verticillioides, in in vitro trials. Trans-2-hexenal was the best pathogen inhibitor, followed by carvacrol and eugenol. In maize kernels, fumigations with trans-2-hexenal provided a high inhibitory effect on F. verticillioides growth and its efficacy depended on concentration and time of incubation. The most effective dose of trans-2-hexenal was 369 microL/L, but this concentration induced off-odour in maize. The exposure to 246 microL/L trans-2-hexenal provided the best control of F. verticillioides and no phytotoxic symptoms or off-odour in kernels was observed. In contrast trans-2-hexenal fumigations were ineffective in the reduction of fumonisin concentration and high concentration (369 microL/L) stimulated fumonisin levels. Reduction or delay in the germinability of the kernel was observed after trans-2-hexenal exposure. The results showed that trans-2-hexenal postharvest fumigation is effective in F. verticillioides control also in asymptomatic maize kernels, but cannot reduce fumonisin production.

Activity of trans‐2‐hexenal against Penicillium expansum in ‘Conference’ pears

Aims:  To investigate the effects of trans‐2‐hexenal on blue mould disease, patulin content and fruit quality in ‘Conference’ pears.

New Approaches for Postharvest Disease Control in Europe

Alternative methods to fungicide treatments have been studied in order to prevent fruit losses in the postharvest phase. Within these methods the applications of: (a) biological control agents (BCAs), (b) plant bioactive compounds, and (c) physico-chemical methods showed interesting results but still far from a practical application in Europe. Actually, despite the substantial progress obtained with BCAs, any biofungicide has been registered in Europe to control postharvest pathogens, moreover because of their insufficient and inconsistent performance. The use of plant bioactive compounds has shown that the treatment conditions (concentration, form of application, formulation, exposure time, time of treatment, etc.) can deeply influence their efficacy. The different responses found in many studies indicate a cultivar specificity in the product-pathogen-volatile interaction. A barrier to use the plant bioactive compounds may not be efficacy, but rather the off-odours caused in fruits and vegetables and/or the phytotoxicity. Physico-chemical methods include heat, ionising and ultraviolet C irradiation, food additives inducers of resistance. Heat treatments by hot water dips, hot dry air, vapour heat or very short water rinse and brushing appear promising. To overcome the drawbacks that have arisen with the these methods, the integration of the antagonist with other treatments such as low toxic substances (GRAS), heat, etc. has been proposed; this strategy could produce an additive or synergistic effect on disease control and obtain satisfactory levels of disease reduction.

Some factors influencing patulin production by Penicillium expansum in pome fruits.

BACKGROUND The objective of our study was to examine the effects of Penicillium expansum on patulin production in relation to isolates, species and cultivar type, incidence and severity of decay. In addition, patulin production at different incubation times and its diffusion were also investigated. These factors were evaluated in pome fruits inoculated with P. expansum and kept at 20 °C for short periods of time. RESULTS The ability of five P. expansum isolates to grow and produce patulin in inoculated Golden Delicious apples varied among the strains from below the limit of quantification to 662 µg kg(-1). Variety and species of pome fruits influenced patulin production. P. expansum isolate PE97.IT produced a higher patulin content in apples than in pears. The highest patulin production was 386 µg kg(-1) in Golden Delicious. No blue mould symptom appeared in pears inoculated with P. expansum and no patulin was detected after 3 days at 20 °C. However, patulin increased with incubation time after 6 and 8 days. No patulin was detected in healthy pear tissue but it was high in the decayed area. CONCLUSION Since patulin production is associated primarily with infected rotten tissue, patulin control is possible by using healthy fruits, sorting damaged and rotten fruits before processing.