Natürliche Mechanismen der Unkrautunterdrückung in ‚Elstar‘-Apfelanlagen

ZusammenfassungIm Rahmen einer Masterarbeit sollte untersucht werden, warum der Baumstreifen in ausgewachsenen Elstar-Anlagen wesentlich weniger Aufwuchs aufweist als bei anderen Apfelsorten auf der gleichen Unterlage am gleichen Standort. Daher wurde die Vegetation in Baumstreifen von ‘Elstar’-Anlagen im Vergleich zu drei anderen Apfelsorten in 150 Vegetationsaufnahmen an drei Terminen in einjährigen Untersuchungen am Campus Klein-Altendorf bonitiert. Daneben wurde die Lichtdurchlässigkeit der Baumkrone mittels 300 Ceptometer- und 100 Schachbrettmessungen der Sonnenflecken im Baumstreifen im Juni und September – nach der Herbizidapplikation im Mai 2019 – ermittelt.Die mit der Schachbrettmethode bzw. mit dem Ceptometer ermittelte Lichteinstrahlung durch die Baumkrone auf den Baumstreifen unter den ‘Elstar’-Apfelbäumen war im September um ca. 35 % bzw. ca. 10 % signifikant geringer als unter Bäumen gleichen Alters der Sorte ‘Golden Delicious’ in der Nachbarreihe auf der gleichen Unterlage M 9.Der Baumstreifen unter ausgewachsenen ‘Gala’- und ‘Braeburn’-Apfelbäumen wies einen statistisch signifikant höheren Bodenbedeckungsgrad mit Beikräutern mit Boniturnoten von 3,8–4,3 im Vergleich zu 1,7–1,9 bei ‘Elstar’ auf (auf der Skala 1–5) – auf zwei nach IP-Richtlinien und einer biologisch bewirtschafteten Fläche, d. h. die Art der Baumstreifenbehandlung (chemisch oder mechanisch) hatte keinen Einfluss auf das Phänomen der Beikrautunterdrückung bei ausgewachsenen ‘Elstar’-Apfelbäumen.Sowohl Kreuzkraut (Senecio spp.) als auch Gänseblümchen (Bellis perennis) traten in den Baumstreifen unter ausgewachsenen ‘Elstar’-Apfelbäumen mit wesentlich geringerer Stetigkeit auf als unter ‘Golden Delicious’ in der benachbarten Reihe. Die in der Literatur beschriebene indirekte Selektion durch langjährige Glyphosatanwendung auf Vogelmiere (Stellaria media) und Kreuzkraut (Seneccio spp.) durch Auskeimen der Samen nach der Herbizidapplikation wurde bestätigt; im vorliegenden Versuch traten jedoch Behaartes Schaumkraut (Cardamine hirsuta) und Rispengräser (Poa spp.) stärker auf.Keimtests in Aussaatschalen – aufgestellt in den Baumstreifen – unter den Apfelbäumen der beiden Apfelsorten ‘Elstar, Michielsen’ und als Vergleich ‘Golden Delicious’ mit einem Licht- (Lepidium sativum) und einem Dunkelkeimer (Borago officinalis) zeigten keinen Unterschied in der Keimrate. Keimtests mit Kressesamen (Lepidium sativum) in mit Falllaub vermischtem Substrat in Aussaatschalen im Gewächshaus zeigten keine keimhemmende und damit keine allelopathische Wirkung des Falllaubes der Sorte ‘Elstar’.Die vorliegenden Ergebnisse der Beikrautunterdrückung im Wiederaufwuchs nach Beikrautbekämpfung stimmen mit denen unter starkwüchsigen ‘Ingrid Marie’ auf M 2 aus der Literatur überein. Diese Wirkung ausgewachsener Apfelbäume der Sorte ‘Elstar, Michielsen’ auf M 9 ist durch die Schattierung dieser wüchsigeren Bäume bedingt und hängt nicht von der Bewirtschaftungsform (IP mit Herbizideinsatz oder Öko mit mechanischer Beikrautbekämpfung), aber eventuell noch von weiteren Faktoren, ab.

Membrane Fatty Acids And Physiological Disorders in Cold Stored ‘Golden Delicious’ Apples Treated with 1-MCP and Calcium Chloride

The present research intents to study the evolution of the skin fatty acids and physiological disorders through cold storage in ‘Golden Delicious’ apples treated with 1-MCP and calcium. Harvested fruit were treated with calcium chloride (Ca), 1-MCP (MCP), Ca+MCP or no treatment (control) then subjected to cold storage at 0.5 ºC for 6 months. Fatty acids composition, Malondialdehyde (MDA) and the physiological disorders bitter pit (BP), superficial scald and diffuse skin browning (DSB) were measured at harvest and after storage plus 7 days shelf-life at room temperature ≈22 ºC. Palmitic acid decreased and linoleic acid increased through time, while oleic and stearic acids had few changes. Unsaturated/saturated fatty acids and MDA increased through time, despite Ca and Ca+MCP were related to lower MDA and lower BP and rotten fruit, after cold storage and shelf-life. In those treatments, the unsaturated/saturated fatty acids were higher, mainly due to higher linoleic acid and lower palmitic acids. Further research is needed to clarify the changes in membrane properties and the effect of some treatments in response to chilling injury through storage.

Phenolics and Mineral Elements Composition in Underutilized Apple Varieties

(1) Background: The aim of this research is to study the importance of improving knowledge of old variety apples in terms of phytochemicals, antioxidant capacity and mineral elements. (2) Methods: Fifteen phenolic compounds (UHPLC-MS/MS techniques), eight mineral elements (Ca, K, Cu, Mn, Fe, Zn, Na and Mg), antioxidant capacity (DPPH%) and vitamin C content in four ancient apple varieties of Tuscany (‘Mora’, ‘Nesta’, ‘Panaia’ and ‘Ruggina’), with the ‘Golden Delicious’ cultivar as reference, were analyzed. (3) Results: Ancient cultivars exhibited a superior antioxidant capacity compared to commercial cultivars. ECTC and CGA were the polyphenols that mostly characterized the ancient apples. The contents of the elements of concern, Zn and Mn, were higher in the ancient cultivars ‘Panaia’ and ‘Ruggina’, while Na showed significant low concentration in ‘Nesta’, ‘Panaia’ and ‘Ruggina’ compared to ‘Golden Delicious’. The vitamin C content also indicated that ‘Mora’, ‘Panaia’ and ‘Ruggina’ old variety had an AsA content around 10 times higher than the ‘Golden Delicious’ apple. (4) Conclusions: Underutilized varieties could be an excellent source of bioactive phenolic phytochemicals, mineral nutrients and vitamins that may offer special nutraceutical benefits compared to other fruits.

Simple Method for Apples’ Bruise Area Prediction

From the producers’ point of view, there is no universal and quick method to predict bruise area when dropping an apple from a certain height onto a certain type of substrate. In this study the authors presented a very simple method to estimate bruise volume based on drop height and substrate material. Three varieties of apples were selected for the study: Idared, Golden Delicious, and Jonagold. Their weight, turgor, moisture, and sugar content were measured to determine morphological differences. In the next step, fruit bruise volumes were determined after a free fall test from a height of 10 to 150 mm in 10 mm increments. Based on the results of the research, linear regression models were performed to predict bruise volume on the basis of the drop height and type of substrate on which the fruit was dropped. Wood and concrete represented the stiffest substrates and it was expected that wood would respond more subtly during the free fall test. Meanwhile, wood appeared to react almost identically to concrete. Corrugated cardboard minimized bruising at the lowest discharge heights, but as the drop height increased, the cardboard degraded and the apple bruising level reached the results as for wood and concrete. Contrary to cardboard, the foam protected apples from bruising up to a drop height of 50 mm and absorbed kinetic energy up to the highest drop heights. Idared proved to be the most resistant to damage, while Golden Delicious was medium and Jonagold was least resistant to damage. Numerical models are a practical tool to quickly estimate bruise volume with an accuracy of about 75% for collective models (including all cultivars dropped on each of the given substrate) and 93% for separate models (including single cultivar dropped on each of the given substrate).

Metamitron, a Photosynthetic Electron Transport Chain Inhibitor, Modulates the Photoprotective Mechanism of Apple Trees

Chemical thinning of apple fruitlets is an important practice as it reduces the natural fruit load and, therefore, increases the size of the final fruit for commercial markets. In apples, one chemical thinner used is Metamitron, which is sold as the commercial product Brevis® (Adama, Israel). This thinner inhibits the electron transfer between Photosystem II and Quinone-a within light reactions of photosynthesis. In this study, we investigated the responses of two apple cultivars—Golden Delicious and Top Red—and photosynthetic light reactions after administration of Brevis®. The analysis revealed that the presence of the inhibitor affects both cultivars’ energetic status. The kinetics of the photoprotective mechanism’s sub-processes are attenuated in both cultivars, but this seems more severe in the Top Red cultivar. State transitions of the antenna and Photosystem II repair cycle are decreased substantially when the Metamitron concentration is above 0.6% in the Top Red cultivar but not in the Golden Delicious cultivar. These attenuations result from a biased absorbed energy distribution between photochemistry and photoprotection pathways in the two cultivars. We suggest that Metamitron inadvertently interacts with photoprotective mechanism-related enzymes in chloroplasts of apple tree leaves. Specifically, we hypothesize that it may interact with the kinases responsible for the induction of state transitions and the Photosystem II repair cycle.

Effects of Thermal and High-Pressure Processing on Quality Features and the Volatile Profiles of Cloudy Juices Obtained from Golden Delicious, Pinova, and Red Delicious Apple Cultivars

In this study, juices extracted from three apple cultivars (Golden Delicious, Pinova, and Red Delicious) were stabilized by means of thermal treatment (TT) and high-pressure processing (HPP, 600 MPa 3 min); pH, total titratable acidity, total soluble solids content, color, and viscosity, as well as volatile profile, were investigated. Qualitative characteristics (pH, titratable acidity, colorimetric parameters, viscosity, and volatile profile) results were significantly influenced by both cultivars and treatments; for example, juice viscosity greatly increased after HPP treatment for Golden Delicious, and after both TT and HPP for Pinova, while no influence of stabilization treatment was registered for Red Delicious juices. Regarding the volatile profile, for Golden Delicious cultivar, HPP treatment determined an increase in volatile compounds for most of the classes considered, leading to a supposed quality implementation. For the other two cultivars, the stabilization treatment that better preserved the volatile profile was the HPP one, even if the results were quite similar to the thermal treatment. Further studies are needed to evaluate different time/pressure combinations that could give better results, depending on the specific apple cultivar.

Identification and pathogenicity of Alternaria species associated with leaf blotch disease and premature defoliation in French apple orchards

Leaf blotch caused by Alternaria spp. is a common disease in apple-producing regions. The disease is usually associated with one phylogenetic species and one species complex, Alternaria alternata and the Alternaria arborescens species complex (A. arborescens SC), respectively. Both taxa may include the Alternaria apple pathotype, a quarantine or regulated pathogen in several countries. The apple pathotype is characterized by the production of a host-selective toxin (HST) which is involved in pathogenicity towards the apple. A cluster of genes located on conditionally dispensable chromosomes (CDCs) is involved in the production of this HST (namely AMT in the case of the apple pathotype). Since 2016, leaf blotch and premature tree defoliation attributed to Alternaria spp. have been observed in apple-producing regions of central and south-eastern France. Our study aimed to identify the Alternaria species involved in apple tree defoliation and assess the presence of the apple pathotype in French orchards. From 2016 to 2018, 166 isolates were collected and identified by multi-locus sequence typing (MLST). This analysis revealed that all these French isolates belonged to either the A. arborescens SC or A. alternata. Specific PCR detection targeting three genes located on the CDC did not indicate the presence of the apple pathotype in France. Pathogenicity was assessed under laboratory conditions on detached leaves of Golden Delicious and Gala apple cultivars for a representative subset of 28 Alternaria isolates. All the tested isolates were pathogenic on detached leaves of cultivars Golden Delicious and Gala, but no differences were observed between the pathogenicity levels of A. arborescens SC and A. alternata. However, the results of our pathogenicity test suggest that cultivar Golden Delicious is more susceptible than Gala to Alternaria leaf blotch. Implications in the detection of the Alternaria apple pathotype and the taxonomic assignment of Alternaria isolates involved in Alternaria leaf blotch are discussed.

Grey and Black Anti-Hail Nets Ameliorated Apple (Malus × domestica Borkh. cv. Golden Delicious) Physiology under Mediterranean Climate

The use of anti-hail nets on orchards changes the microclimate underneath the net. This might be of great importance in apple growing regions characterized by high radiation levels and hot and dry climates during the summer season. But, depending on the net colour and on the local climatic conditions, the shade promoted triggers different responses by the trees. Grey and black anti-hail nets were applied in an apple orchard (cv. ‘Golden Delicious’) located in Northeast Portugal. Under the nets a lower concentration of glomalin related-soil proteins was observed, along with an improvement on trees water status, stomatal conductance, net photosynthetic rate, total chlorophylls, N, Mg, Fe and Cu concentrations, as well as an increase in mean fruit weight. The major difference between nets was on the photosynthetic efficiency, being higher on black net in sunny days, while grey net performed better under cloudy conditions. The use of netting systems proved to be effective in improving “Golden Delicious” apple trees performance under a Mediterranean climate, mainly when the radiation reaching the plants surpass the tree saturation point for photosynthesis. Therefore, these findings anticipate solutions for current and forecasted negative effects of climate change.

The effect of post-harvest storage on the weight of Golden Delicious apples

Apples, like other fruits, are exposed to stress during their growth and development in the field, also during harvest and the postharvest environment (processing, storage, and transportation). The refrigeration system allows for bulk handling of food products from harvest to market, ensuring that food products are maintained in their freshness and integrity for an extended period through careful management of storage temperature and humidity. This study investigated the effects of storage on the weight loss of apples (Golden Delicious fruits harvested at maturity), under refrigerated conditions at a temperature of 5±0.5°C and relative humidity of 82% and under ambient storage at a temperature of 25 ±0.5 °C and relative humidity of 60 %, over 3 months. The findings revealed that the two groups of apples experienced weight reduction at different levels. Apples placed at cold storage presented a loss of weight between 3.31g and 4.49g; however, apples stored at ambient temperature showed a significant loss of weight between 21.9g and 31.76g.