Superficial scald is a postharvest physiological disorder of apples characterized by browning of apple skin during prolonged storage. It has been hypothesized that conjugated triene hydroperoxides (CTH) attack cell membranes causing membrane perturbation and the manifestation of the disorder. The purpose of this study was to compare the common synthetic antioxidant diphenylamine (DPA) treatment with postharvest vapour treatments for superficial scald prevention. Apples cv. ‚Granny Smith™ were treated with ethanol, methanol and »apple aroma« vapours. The influence of these treatments on scald susceptibility and sensorial quality of apples was examined. The ethanol treatments were effective in superficial scald prevention but they caused a high incidence of internal browning after two months of storage. The 10 day treatments at 20 °C developed very pronounced internal browning after storage. The aroma treatment was the least effective in apple scald prevention but no internal disorders appeared after storage. Apples treated with methanol at 20 °C retain a great deal of their initial green colour. Vapour treatments demonstrated to be potential methods for scald prevention. Additional research is needed to minimise the internal disorders of treated fruit.
Authors:S. Trdan, D. Žnidarčič, M. Kač, and M. Vidrih
In 2005 the damage caused by onion thrips
on a susceptible hybrid of early cabbage (cv. ‘Parel’) was studied in a block field experiment. The cabbage was grown in four treatments: 1) on non-mulched surfaces, 2) on surfaces mulched with barley straw, 3) on surfaces mulched with hay and 4) on surfaces mulched with black PE mulch. The trial consisted of two parts: the first part included plots that were mulched as indicated from the very beginning (normal), while in the second part the soil was first covered with black PE mulch for about one month, than this was removed and replaced either by organic mulches or left non-mulched (postponed). In this way, we wanted to diminish the yield loss because of low temperatures and abundant precipitation. Under cold and wet conditions in spring which led to late appearance and low levels of the pest, the growing of cabbage under black PE mulch proved most effective and these plants exhibited the greatest head mass as well as the greatest net mass, although they also suffered most damage from the pest. The cabbage in the second part of the experiment exhibited higher head mass as well as higher net head mass compared to the first part.
Authors:J. Hribal, M. Zavrtanik, M. Simćić, and R. Vidrih
Physiological changes during ripening, storing and astringency removal of persimmon fruits were traced. The fruits were stored under normal (NA), controlled (CA) and vacuum atmospheres (VA). The fruits were stored for 100 days and analysed for firmness, acetaldehyde and ethanol content and soluble tannins, both before and after storing. The same analyses were done during the deastringency treatment carried out with a high CO2 concentration (99.99%) for 20 h at 20 °C. The persimmon fruits stored under NA, CA, VA or treated with high CO2 for 20 h accumulated acetaldehyde and ethanol in the fruit tissue. CA conditions caused the highest acetaldehyde accumulation; vacuum conditions the lowest. Ethanol content increased 20 fold during storage; the highest accumulation was observed in vacuum stored fruit followed by CA (3% CO2&2% O2 and 0.5% CO2&2% O2) conditions. Astringency removal treatment caused an immediate increase of acetaldehyde and ethanol, nearly to the same extent as in conventionally ripened or stored fruit. The amount of soluble tannins, the main cause of an astringent taste, decreased during storage, and it did much faster during deastringency removal at the same level. The sensory evaluation test revealed that fruit treated with high CO2 was preferred to conventionally ripened fruit.
Authors:A. Sreš, S. Trdan, G. Leskošek, M. Vidrih, and F. Vučajnk
The effect of spraying speed (5, 8.5 or 12 km/h) on deposition quality of fungicide on a winter wheat head, yield, grain quality, occurrence of Fusarium head blight (FHB) and deoxynivalenol (DON) content in grains was investigated in 2011 and 2012. Asymmetric double flat fan air-injector nozzles were used in the trial at a spraying pressure of 5.0 bars. A prothiconazole + tebuconazole fungicide mixture was used for spraying. An increase of spraying speed significantly lowered coverage values at the front and rear parts of a wheat head. At all three spraying speeds, the rear part of a wheat head reached a better coverage value. The effect of spraying speed was significant in 2011, when the 5 km/h spraying speed generated a significantly higher grain yield and a significantly higher thousand-grain weight in comparison with the other treatments. In both trial years, the lowest grain yield occurred on the unsprayed control. In 2011 and 2012, the latter also reached the lowest hectolitre weight and thousand-grain weight. In both trial years, the unsprayed control had a significantly higher DONcontent than the other treatments. In 2012, the DONcontent on the unsprayed control exceeded the allowed maximum level. The spraying speed did not affect the DON content in the grains. The effect of spraying speed was also noted in the FHB incidence. A significantly lower FHB incidence occurred at the 5 and 8.5 km/h spraying speeds.
Authors:S. Trdan, N. Valič, L. Andjus, I. Vovk, M. Martelanc, B. Simonovska, J. Jerman, R. Vidrih, M. Vidrih, and D. Žnidarčič
In a field experiment on the natural resistance of cabbage (
) against onion thrips
, 20 cabbage genotypes were included: 9 early, 5 mid-early, 6 mid-late (regarding the longevity of the growing period), 3 red, 17 white (regarding colour), 14 hybrids and 6 varieties (regarding genetic origin). For comparisons between genotypes, we determined significant differences in the mean index of damage on the exterior leaves of cabbage heads (1.12–2.83), the net weight of heads (281.40,151169.6 g), and yield loss (5.8–47.4%). The concentration of several compounds from cabbage leaves (epicuticular wax, α-amyrin, β-amyrin, lupeol, sucrose, glucose, fructose, vitamin C, palmitic acid, stearic acid, and arachidic acid) are measured. For all groups of cabbage genotypes the only confirmed negative correlation was between the extent of damage caused by the sucking of onion thrips and epicuticular wax content on the cabbage leaves (in groups where we artificially placed genotypes with similar characteristics). After this preliminary experiment, the research must be extended in order to determine the effect of the remaining analysed compounds in cabbage leaves for resistance (sensitivity) of cabbage to onion thrips attack.
Authors:F. Vučajnk, S. Trdan, G. Leskošek, I.J. Košir, A. Sreš, D. Kocjan Ačko, and M. Vidrih
In 2014 and 2015, we studied the effect of fungicide spraying with 11 different nozzles on the quality and quantity of head and leaf fungicide deposit, the percentage of Fusarium head blight (FHB) incidence, FHB index, the DON content, yield and grain quality parameters. The best quality and quantity of fungicide deposit on the front and rear head sides was achieved with the TeeJet Turbo FloodJet TF VP2 nozzle (FLOOD) and the Albuz AVI-TWIN 110-03 nozzle (AVI). In comparison with the majority of treatments, the FHB incidence and the FHB index was the highest on the unsprayed control. The FHB index was higher using the Lechler IDK 120-03 nozzle (IDK) than with the other nozzle types. In all the treatments, the DON content in the grain was less than 50 μg/kg. At this very low level of infection this is not surprising. The grain yield was the smallest on the unsprayed control. Better fungicide coverage of wheat heads with the FLOOD and AVI nozzles did not result in a statistically higher yield or better grain quality parameters. Negative correlations were confirmed between yield and variables as DON content, FHB incidence and FHB index and also between falling number and variables as fungicide coverage, FHB incidence and FHB index. Positive correlations were determined between DON content and FHB incidence, between hectolitre weight and variables as spray deposit and coverage and between protein content and variables as spray deposit and coverage.