Ravensburg, Germany
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Harb J.,Birzeit University | Saleh O.,Albert Ludwigs University of Freiburg | Kittemann D.,Kompetenzzentrum Obstbau Bodensee | Neuwald D.A.,Kompetenzzentrum Obstbau Bodensee | And 3 more authors.
Postharvest Biology and Technology | Year: 2013

'Skin burning' of 'Cameo' apples resulting in poorly colored fruit can occur in storage under high CO2 condition. To elucidate possible reasons for this physiological disorder, we assessed the differential expression of polyphenol-related genes. Poorly colored and well-colored mature 'Cameo' apples were stored under either high (3%) or low (0.7%) CO2 levels, both in combination with 1% O2, and monitored for seven months for 'skin burning'. Samples were obtained by the end of storage period, and qPCR analyses were conducted using gene specific primers. We found expression levels of chalcone synthase (MdCHS), chalcone isomerase (MdCHI), anthocyanidin synthase (MdANS), flavonol synthase (MdFLS), dihydroflavonolreductase (MdDFR), and leucoanthocyanidinreductase (MdLAR1) genes to be substantially higher in well-colored compared to poorly colored apples. The delay in establishing the stressful controlled atmosphere (CA) storage condition (3% CO2 level) led to significantly higher expression levels of MdLAR1, MdCHI, anthocyanidinreductase (MdANR) and flavanone 3-hydroxylase (MdF3H), which may explain the lower incidence of 'skin burning' by delayed CA fruit. On the other hand, after seven months in storage, the expression levels of phenylalanine ammonia-lyase (MdPAL), MdCHS, MdCHI, MdDFR, MdFLS, and MdF3H, were significantly higher in poorly colored injured apples, which reflect a feedback mechanism to synthesize more polyphenols to counteract the stressful storage condition. © 2012 Elsevier B.V.

Weber R.W.S.,Esteburg Obstbauzentrum Jork | Weber R.W.S.,University of Aarhus | Spath S.,Kompetenzzentrum Obstbau Bodensee | Buchleither S.,Kompetenzzentrum Obstbau Bodensee | Mayr U.,Kompetenzzentrum Obstbau Bodensee
Erwerbs-Obstbau | Year: 2016

Sooty blotch and flyspeck (SBFS) fungi colonise the surface of a range of fruits, especially apple, without penetrating the cuticle. Economic damage results from the exclusion of severely affected fruit batches from being marketed as table apples. A study of SBFS was conducted in 2007–2012 in the two largest German apple production areas, i.e. the Lake Constance and Lower Elbe regions. The absence of this disease complex from orchards under integrated pest management in both regions in all years was explained by the collateral effects of scab and storage-rot sprays with captan and quinone-outside inhibitors (QoI) such as trifloxystrobin. However, SBFS was economically relevant in organically managed orchards, being generally more severe in Southern Germany than in the North. In both regions, Peltaster cerophilus was the most frequently isolated SBFS fungus and was chiefly responsible for crop losses. Cyphellophora sessilis, Microcyclosporella mali and Schizothyrium pomi also contributed to SBFS in some organic orchards, whereas a diversity of additional species was confined to untreated orchards. Evidence was obtained that P. cerophilus overwinters within orchards, fruit mummies being one of presumably several colonised plant organs. Infections of young apple fruits were initiated at any time following the end of flowering, and P. cerophilus was capable of causing several infection cycles per season by means of conidial inoculum. The colonisation of sheets of waxed paper by P. cerophilus indicated that this species does not require fruit leachates for growth. No further expansion of colonies was observed during cold storage; instead, P. cerophilus was gradually displaced by other fungi. Differences in the susceptibility of apple varieties to P. cerophilus were due to fruit ripening, late-maturing cultivars being most heavily colonised, and to surface properties, varieties with a waxy bloom being conspicuously less strongly colonised than others. This fungus was unable to colonise russeted fruit areas. Repeated spray treatments with lime-sulphur and potassium bicarbonate throughout the season were effective and necessary to control SBFS in organic production. This strategy threatens the fungicide-saving potential offered by scab-resistant apple varieties. Cultural measures against SBFS include summer pruning as well as the manual removal of fruit mummies in winter. © 2016 Springer-Verlag Berlin Heidelberg

Harb J.,Bank of The West | Khraiwesh B.,Vlaams Institute for Biotechnology | Khraiwesh B.,Albert Ludwigs University of Freiburg | Streif J.,Kompetenzzentrum Obstbau Bodensee | And 2 more authors.
Scientia Horticulturae | Year: 2010

Blueberry (Vaccinium corymbosum) is among the richest fruits in ascorbic acid (AA), which is the most important antioxidant involved in the ascorbate-glutathione cycle. In this cycle monodehydroascorbate reductase (MDAR) is the enzymatic component involved in the regeneration of reduced ascorbate. Here we report on the isolation of a full-length cDNA from blueberry encoding a protein of 433 amino acids homologous to the MDARs of Pisum sativum and Vitis vinifera. To assess changes in the expression of blueberry MDAR after harvest, a storage trial was initiated, and the major results were: (1) A dramatic loss in AA occurred under all storage conditions. However, storing fruit under low O2, combined with high CO2 level (up to 18%) resulted in better preservation of AA. (2) The antioxidative capacity of water soluble antioxidants (ACW) decreased under all storage conditions, even after 3 weeks storage time, and decreasing O2 levels did not result in preservation of the ACW. The northern blot hybridization showed a clear differential expression between freshly harvested and stored fruits as well as between fruits stored under various storage condition, in accordance with the above-mentioned changes. In conclusion, this study clearly indicates that consumption of freshly harvested blueberries is highly recommended over the stored berries. Moreover, further work is needed to elucidate reasons for the quality loss over the storage period, in particular at the molecular level. © 2010 Elsevier B.V. All rights reserved.

Harb J.,Bank of The West | Khraiwesh B.,Albert Ludwigs University of Freiburg | Streif J.,Kompetenzzentrum Obstbau Bodensee | Reski R.,Albert Ludwigs University of Freiburg | Frank W.,Albert Ludwigs University of Freiburg
Acta Horticulturae | Year: 2010

Blueberry is considered as one of the richest fruit types in ascorbic acid (AA), and is highly recommended for a healthy diet. In plant tissues mono-dehydro-ascorbate reductase (MDAR) is the enzyme involved in the regeneration of oxidized ascorbate, which is produced after the detoxification of free radicals. Taking into account the importance of this enzyme and using the gene fishing technique, a partial PCR-product of the gene encoding MDAR was isolated. Subsequently the 5-RACE PCR technique was employed to complete the characterization of this gene, and a sequence of 1551 bp was identified with a deduced protein that contained 433 amino acids. The sequence showed high homology to MDARs of Psium sativum and Vitis vinifera. Northern blot hybridization was employed to assess the gene expression of this gene upon storage of blueberries under various controlled atmosphere (CA) conditions. Results clearly showed differential expression between freshly harvested versus stored fruit as well as among fruit stored under various CA conditions. Quantitative assessments of ascorbic acid and the antioxidative capacity of water soluble antioxidants (ACW) revealed a dramatic loss in ascorbic acid under all storage conditions, even after three weeks in storage. The ACW decreased under all storage conditions and low O 2 concentrations did not enhance preservation of ACW. However, 2% O 2 combined with 6-12% CO 2 gave significantly better preservation of ACW than cold air storage. Northern blot hybridization results were in general agreement with the quantitative assessments of AA and ACW.

Bangerth F.K.,University of Hohenheim | Song J.,Agriculture and Agri Food Canada | Streif J.,Kompetenzzentrum Obstbau Bodensee
HortScience | Year: 2012

After a brief description of the "history of research" of aroma volatiles of apple and strawberry fruit, possible reasons for the reduced production of these important quality attributes by particular pre- and postharvest procedures are given. Among the possible physiological factors in association with reduced aroma volatile production, a reduced ethylene sensitivity, a decline in the rate of respiration as well as the content of adenine nucleotides and limited free fatty acids as precursors for aroma volatiles biosynthesis are proposed. A hypothesis about how this sequence of events leads to reduced volatile production is given and finally some suggestions of how to improve volatile synthesis are discussed.

Kittemann D.,Kompetenzzentrum Obstbau Bodensee | Neuwald D.A.,Kompetenzzentrum Obstbau Bodensee | Streif J.,Kompetenzzentrum Obstbau Bodensee
Acta Horticulturae | Year: 2010

Softening processes in apples during storage and shelf-life are related to cell wall degrading enzymes involved in the hydrolysis of cell wall components. Calcium also has a role in cell wall stability as calcium treatments can extend storage life, decrease fruit softening rate, and reduce both respiration and ethylene production. Our experiment investigates the influence of calcium infiltration in combination with different storage treatments, including the use of 1-MCP, on the softening behaviour of 'Elstar' apples. We measured the activity of the cell wall degrading enzymes (endo-(1-4)-β-D-glucanase; polygalacturonase; pectate lyase; pectin methylesterase) to explain differences in fruit softening rates. Calcium treatments decreased respiration, ethylene production and fruit softening, but increased cell wall degrading enzyme activity. In general, the effect of calcium infiltration treatments on the measured parameters was comparable to the effect of 1-MCP.

Wang R.,Northwest Agriculture and Forestry University | Xuan H.,Kompetenzzentrum Obstbau Bodensee | McCormick R.,Kompetenzzentrum Obstbau Bodensee | Streif J.,Kompetenzzentrum Obstbau Bodensee
Acta Horticulturae | Year: 2012

This work evaluates the effect of a short-term CO2 treatment on the postharvest quality during shelf-life at room temperature of European plum (Prunus domestica) cultivars 'Hanita' and 'Elena' harvested at different ripening stages. 'Hanita' behaved as a climacteric fruit, 'Elena' behaved as a 'suppressed' climacteric fruit in which there were no obvious ethylene or respiration rate peaks measured during shelf-life at room temperature. Short term exposure to high CO2 did not have any effect in extended shelf-life of 'Elena' plum fruit, but accelerated the deterioration of 'Hanita'.

Kittemann D.,Kompetenzzentrum Obstbau Bodensee | Neuwald D.A.,Kompetenzzentrum Obstbau Bodensee | Streif J.,Kompetenzzentrum Obstbau Bodensee
Acta Horticulturae | Year: 2010

Sweet cherry is a fruit with a very limited storage life and fungal decay during shelf-life can often result in serious fruit loss. In Germany, there are no postharvest treatments allowed to control fungal diseases on sweet cherries. However, internationally interest is increasing in alternative methods that are harmless to consumer health. We tested different GRAS (Generally Recognized As Safe) methods to control Penicillium expansum (blue mould rot), Botrytis cinerea (gray mould rot) and Monilinia fructigena (brown rot) on sweet cherry in 2007 and 2008. Comparing the different GRAS methods, a combination of sodium bicarbonate (NaHCO3) and yeast (Aurebasidium pullulans), a product marketed as AntinfekTM10H (polyhexamethylene biguanidine hydrochloride 3.2% w/w), a combination of AntinfekTM with Serenade Max (Bacillus subtilis), and AntinfekTM with calcium hydroxide, all showed good results in reducing postharvest fungal diseases. Other GRAS methods, such as citric acid, calcium formate, Na-metasilicate, chitosan, or yeast separately did not show adequate control against the tested fungi. Further GRAS research to control postharvest diseases in sweet cherry is planned.

Sharma K.,Czech University of Life Sciences | Xuan H.,Kompetenzzentrum Obstbau Bodensee | Sedlak P.,Czech University of Life Sciences
Biochemical Systematics and Ecology | Year: 2015

We analyzed 24 sweet and wild cherry genotypes collected in Czech Republic to determine genetic variation, using previously described 16 SSR primers to adapt a fast, reliable method for preliminary screening and comparison of sweet cherry germplasm collections. All SSRs were polymorphic and they were able all together to distinguish unambiguously the genotypes. These SSR primers generated 70 alleles; the number of alleles per primer ranged from 2 to 7, with a mean of 4.4 putative alleles per primer combination. The primer UDP-98-412 gave the highest number of polymorphic bands (totally 7), while Empa2 and Empa3 gave the lowest number (2). The allele frequency varied from 2.1% to 87.5%. We observed 10% of unique alleles at different loci. The observed heterozygosity value ranged from 0.25 to 0.96 with an average of 0.72 while expected heterozygosity value varied from 0.22 to 0.75 with an average of 0.59. The PIC value ranged from 0.21 to 0.71 with a mean value of 0.523. Cluster analysis separated the investigated cultivars in two groups. High level of genetic diversity obtained in the collection and proved to be sufficiently genetically diverse and therefore these genotypes would be useful to breeders for the development of new cherry cultivars. © 2015.

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