Goran Fruk

Effects of Ocimum spp. essential oil on Monilinia laxa in vitro

One of the most important postharvest diseases of peach and nectarine is brown rot caused by the fungus Monilinia laxa. Increasing concern related to the toxic effect of the pesticide residues on fruits has enhanced the interest for the control of postharvest pathogenic fungi using biologically active constituents of plants such as essential oils. Species from genus Ocimum are known to possess essential oils with antifungal and fungicidal properties. The present paper reports the results of essential oil composition of four basil taxa and preliminary screening of their antifungal activity against M. laxa. The greatest effectiveness was achieved by the essential oils from Ocimum basilicum var. purpurascens and Ocimum tenuiflorum, whose activity was high throughout the testing period of twenty-three days.

First Report of Tilletiopsis pallescens Causing White Haze on Apple in Croatia

During 2014, apples ‘Pink Lady®’, showing white haze (WH) symptoms, were harvested in an orchard near Vratisinec (Croatia). Fungi were isolates from symptomatic epidermal tissue on Rose Bengal Chloramphenicol agar. After 7 days of incubation in the dark at 26°C, from whitish to cream colonies with irregular margin, single spore were isolated and transferred on Potato dextrose agar (PDA). Pathogenicity was tested on 20 apples ‘Pink Lady®’ and the pathogen was inoculated by aerosol diffusion on the sterilized surface. Symptoms occurred and T. pallescens was reisolated from inoculated fruit on PDA. Control fruits were symptomless. After 7 days at 26°C, the colonies and the morphology of conidia were the same as those of the original isolates. PCR amplification was carried out, from single spore DNA extraction, using universal primers ITS1 and ITS4. Two amplified sequences (AN KR269863 and KR269864) were blasted in Genbank obtaining 100% homology with strains of Tilletipsis pallescens. To confirm the species DNA sequences were aligned with CLUSTAL W with closely related species of Tilletiopsis (T. pallescens GQ281316.1, DQ317636.1 ; T. washingtoniensis DQ025483.1 ; T. lilacina AB025683.1, AB025689.1T ; T. cremea AB025690.1 ; and an undefined species Tilletiopsis sp. GQ281313.1) and a phylogenetic analysis with the Neighbor Joining method based on Maximum Composite Likelihood model (bootstrap 1, 000) was performed (supplementary material). The phylogenetic tree confirmed the identity of the isolates to the species Tilletiopsis pallescens. To our knowledge, this is the first report of Tilletiopsis pallescens causing postharvest white haze on apple in Croatia.

In vitro pollen germination and pollen tube growth differences among Quercus robur L. clones in response to meteorological conditions

Abstract The impact of meteorological conditions on in vitro pollen germination and pollen tube growth during the initial phases of the development of male flowers in the Pedunculate Oak, Quercus robur, is studied. Phenological observations of male flowers and pollen sampling were performed on the field trial established with grafted Pedunculate Oak clones. During the investigation, weather conditions (absolute minimum and maximum daily air temperature, minimum absolute relative humidity of air and amount of precipitation) were recorded by an automatic meteorological station installed at the field trial. Influence of meteorological conditions on pollen germination and pollen tube growth was studied in the following stages of male flower: (I) during the last ten days of flower bud dormancy, (II) during swelling of the buds, (III) during bud burst and beginning of male catkins elongation, (IV) during the final stage of male flower catkins elongation. High temperatures and low relative air humidity during the bud burst and beginning of the male catkins elongation reduced pollen germination and pollen tube growth. Weather conditions did not significantly affect pollen germination and pollen tube growth during the swelling of flower buds, or in the final stage of male catkins elongation.

Colouration of Apple cv. ‘Braeburn’ Grown Under Anti-Hail Nets in Croatia

Abstract Four anti-hail and anti-insect nets (red, white and yellow anti-hail and Stop Drosophila Normal) were used on apple cv. ‘Braeburn’ grown in northern Croatia in order to evaluate their effect on fruit colouration that was measured with the colorimeter (expressed as: L* – lightness, a* – yellow/blue b* – green/red) on two sides of fruit (“green” side and “red” side), and also they were used in order to evaluate their effect on the coloured surface percentage, apart from their anti-hail and pest damage protection properties. The fruits were harvested on 12th October 2015. Most differences were found between the fruit grown under the white anti-hail net and the fruit grown without the anti-hail net. Colour value “a*” was lower on the red side of the fruit under the white net in comparison with the red net. On the green side, “a*” value was lower and “L*” value was higher under the white net in comparison with control fruit. Different net colour had no influence on total colour difference. Regarding to the colouration, differences among the nets are found in classes 0–25% and 50–75% of skin coloured fruit. The fruit grown under the white nets had the higher percentage of fruit in class 0–25% than those grown without the net. The lower share of fruit in class 50–75% of skin colouration was recorded under the white net than under the red net or in the control fruit. Colouration index was lower in the fruit grown under the white net than in the control fruit. It can be concluded that the white anti-hail net promotes ripening, but at the same time it decreases red colouration. No significant differences in fruit colour have been found in the fruit grown under the red, yellow and Stop Drosophila Normal nets. Some accepted colour parameters such as a*/b* ratio are not appropriate for describing colour changes in ‘Braeburn’ apple in this study.