A 40% increase in the production of Norwegian apples was anticipated from 2018 to 2023; this volume was already reached in 2021. Handling of such a volume requires optimal fruit quality and careful treatment at harvest, improved environmental conditions for short- and long-term cold storage, and better communication within the apple industry. The project Eple-Handling has facilitated collaboration in the whole value chain of apple production, and focused on reducing the incidence of physiological disorders and fungal decay of the fruit. A PhD student is expected to finish in June 2025. A MSc student delivered a thesis in 2023 and was recruited as a researcher with the demand of further qualifying through a PhD. Network activities have been performed with Nordic and Baltic countries, and Germany.
The experimental work for the PhD included experiments with connections between calcium, ethylene, storage temperature and maturity. Foliar fertilization with calcium did not have effect on fruit storability.
Harvest time and use of an ethylene receptor blocker (1-MCP) influenced the fruit quality strongly, but damage development was too minimal to show differences at 4°C. When stored at -0.5°C there was more damage and a clear effect of harvest time on incidence. Fruit of the main cultivar in Norway, Red Aroma, was harvested and stored in Germany as well to evaluate the effect of local climate on disorder development. Molecular tools (RT-qPCR and transcriptomics) in combination with fruit quality and damage complete the base for the PhD.
Different chemical spraying strategies against storage rot were tested in Germany and Norway. On fruit stored for six months in Germany, there was a good effect of Delan over three seasons, even though the last application was 21 days prior to harvest. Brown rot and grey mould were the dominating diseases at grading in Norway. On assessments in Germany of Botrytis spores from Norwegian apple fruit, there was a relatively low incidence of fungicide resistance. Incidence of fungal decay on fruit from different packinghouses and seasons showed differences with seasons, cultivars and storage time. In a separate experiment in Germany comparing cultivars, the same results with season differences as well as cultivar differences were obtained.
A method for screening of mycotoxins in juice was established. Juice made of fruit with core rot of Fusarium had findings of toxins related to Fusarium. The amount was variable between experiments and more experiments are needed to evaluate risk in Norwegian apple products.
The most common mycotoxin in apple juice is patulin. In two years, juice was made with inoculated fruit at different times after inoculation. The risk of patulin in the juice was considered low if non-wounded and healthy appearing fruit were used, and if the fruit were kept cold before processing. The content of patulin doubled after three days at 20°C.
Temperature, relative humidity, and ethylene concentrations in storage rooms at packinghouses were measured in 2020 together with fruit quality. Due to a low yield level of apples in 2020, new measurements were performed yearly in 2021-2023 as part of the associated project FruktKlima (NFR 317763). Air volume and distribution and energy usage for the different packinghouses were determined. In 2021 high values of ethylene were measured at all packinghouses with full rooms. In experiments at NIBIO, ethylene production of all the main cultivars in combination with 1-MCP treatment was evaluated in an expected period of cold storage and in simulated shelf life. There were differences between cultivars, and the production increased with time and temperature.
Long-term storage in controlled atmosphere was tested with cv. Rubinstep at one packinghouse and with cvs. Rubinstep and Elstar at NIBIO. Fruit quality results was promising in all years, but the incidence of damage was higher than expected in some of the experiments. Shorter term CA of cv. Red Aroma was tested at two packinghouses in 2021 and in combination with use of 1-MCP in 2022 and 2023. The results were very promising and after approval of 1-MCP in Norway in 2024, have given the packinghouses tools to ensure consumer acceptable quality of cv. Red Aroma at least until December. Economic evaluations were completed as a part of FruktKlima.
Whole value chain communication was initiated and maintained by meetings, excursions, physical meetings, and an online packinghouse school. In total 7-11 webinars with 3-4 topics each time were held each year as a packinghouse school. Before each growing season a meeting for all participants was held. Writing and summarizing are in progress. Results important for the fruit growers have been communicated in additional meetings and through seminars.
A 40% increase of the Norwegian apple production is anticipated over the coming five years. This will require optimal quality fruit and careful treatment at harvest, improved environmental conditions for short- and long-term cold storage, and a better communication within the apple industry. Eple-Handling will facilitate collaboration in the whole value chain of the apple production, with focus on reducing the incidence of physiological disorders and fungal decay of the fruit. Physiological disorders will be reduced by increasing the awareness and competence about their causes, optimize orchard conditions, and combine technological, physical, biological and economic knowledge to improve storage management. There will be a special emphasis on fruit calcium content, optimized harvest time and cooling in the early storage phase, with an overall aim to slow the fruit maturation processes. Fruit decay in Norway are caused by numerous fungal pathogens, and Eple-Handling will improve our understanding of pathogen biology, reveal pre- and postharvest sources of inoculum and environmental conditions that cause infection and disease development. Furthermore, Eple-Handling will investigate the postharvest stimulation of pathogens on formation of ethylene and mycotoxins, with subsequent adverse effects on fruit maturation and juice contamination, respectively. The project will be devoted to improving both short- and longer-term storage conditions. An existing or new software program will be adapted to follow the fruit from the orchard via storage to the market, and thus contribute in revealing fruit qualities and critical points of improvement at individual farms and the packinghouses. The project will include education of a PhD as well as MSc students in Norway and form a network of research and educational activities with PhD-students and scientists in Sweden and Germany.