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Strawberries are a very important economic crop; thus, a lot of research has been conducted on several production areas. However, phenological performance is still lacking information, especially when it comes to modeling. Therefore, this study aims to develop a phenological model for flower–fruit development under hydroponic conditions to support growers’ decision-making. Two day-neutral cultivars, ‘Albion’ and ‘San Andreas’, were established in a drip hydroponic system in Auburn, Alabama for the 2022–2023 production season. Phenological data were collected daily on 30 flowers per cultivar for three periods (Oct 25–Dec 16, Dec 27–Feb 21, and Feb 28–Apr 16). Weather data were obtained from a weather station placed in the greenhouse. Growing degree days (GDD) accumulation was calculated for each stage and cycle using a base temperature (Tb) of 3 °C. The Gaussian model was adjusted for each stage and cycle using a non-linear procedure to obtain Gaussian curves. Simulations were made for the model assuming temperature would increase or decrease by 1 °C. Six stages were identified, and their cycle ranged from 43–56 days to be accomplished. ‘Albion’ needed more days to reach maturity, with 51, 56, and 47 days, and ‘San Andreas’ took 43, 54, and 46 days for cycles 1, 2, and 3 respectively. In addition, for cycles 1 and 2, not all the buds reached maturity, as expected. Stage 5 (fruit formation) needed more days than the rest of the stages to be completed. Because of the different starting dates for each cycle, the starting GDD was different as well. A sensitivity analysis simulation of the model showed that if temperature decreases by 1 °C, the GDD accumulated to complete the stages would be less (same dates), and it would be more if the temperature increased by 1 °C. The opposite happened with the days, if the temperature increased by 1 °C, the duration of the stage decreased, and it would increase if the temperature decreased by 1 °C, affecting stages 4, 5, and 6. Overall, ‘San Andreas’ performed better than ‘Albion’ under hydroponic conditions during three productive cycles.

The commercial apple production in Norway is limited to the small regions along the fjords in the southwest part of the country and around lakes or near the sea in the southeast with favorable climate. Due to the rapid rate of climate change over the recent decades, it is expected that suitable heat conditions for apple growing will expand to the areas that were previously too cold. This study analyses the heat suitability of future climate (2021–2100) under the RCP8.5 scenario for 6 common apple varieties in Norway: Discovery, Gravenstein, Summerred, Aroma, Rubinstep and Elstar. Previously established heat requirement criteria (based on the temperature threshold for the full blooming and growing degree days sum between the full bloom and harvest) are applied to the temperature outputs of the regional climate models downscaled to 1 km resolution. The assessment indicates that as temperature rises, heat conditions suitable for cultivation of all 6 apple varieties will expand. According to the ensemble median value, areas with the favorable heat conditions for growing at least one of the considered apple varieties will increase 25 times in the period 2021–2040 and 60 times in the period 2041–2060, compared to the referent period 1971–2000. At the same time, areas suitable for all 6 apple varieties will increase 3 times in the first, and 3.8 times in the latter period. The favorable areas will advance from south and southeast northwards and inland in the eastern region, along the west and northwestern coastline towards higher latitudes, and along continental parts of fjords. The fastest expansion of heat suitable conditions is expected for Discovery and Gravenstein. The findings of this study are relevant for zoning apple production future potential and for strategical planning of climate change adaptation measures within the sector. Weather-related risks, such as risks from winter low temperatures, spring frost, drought and extreme precipitation were not considered.

Aim: This research aimed to: (1) investigate the relationships between harvest dates and berry composition with air temperature during important periods during the growing season, across a range of indigenous and international winegrape varieties grown in wine regions over the majority of Greece; (2) calculate growing degree-days (GDD) from 1st of April until the harvest date of each variety and group the winegrape varieties according to their heat requirements; and (3) predict future harvest dates based upon these heat requirements under different representative emission pathways (i.e., RCP4.5 and RCP8.5) and future time periods (2041-2065 and 2071-2095) using an ensemble projection dataset. Methods and results: The analysis of heat requirements based on GDD from 1st of April to harvest date identified consistent maturity groups of the varieties studied, especially for indigenous Greek varieties. Trend analysis using the basic linear regression model showed that harvest dates have shifted earlier, during the last few decades, due to warmer conditions (especially during the ripening period) in most cases. In addition, trends in potential alcohol (acid) levels were found to be positively (negatively) correlated with maximum air temperatures in the majority of cases. Analysis of future projections using a global multi-climate model ensemble dataset (10 regional climate models) showed that harvest dates are projected to shift earlier up to 40 days in two future time periods (i.e., 2041-2065 and 2071-2095) depending on the variety and the emission pathway. Conclusions: Harvest dates of the early ripening varieties were associated more with the variations in maximum air temperatures during March to July, while mid- and late ripening varieties appeared to be affected more by maximum air temperatures during the ripening period. In addition, late ripening, mostly indigenous, varieties were less impacted by temperature increases compared to international varieties. Significance of the study: The indigenous Greek varieties appear better adapted to the recent and projected future climate of the region, responding less to warming as compared to international varieties in the majority of the study cases.

Aim: This research aimed to: (1) investigate the relationships between harvest dates and berry composition with air temperature during important periods during the growing season, across a range of indigenous and international winegrape varieties grown in wine regions over the majority of Greece; (2) calculate growing degree-days (GDD) from 1st of April until the harvest date of each variety and group the winegrape varieties according to their heat requirements; and (3) predict future harvest dates based upon these heat requirements under different representative emission pathways (i.e., RCP4.5 and RCP8.5) and future time periods (2041-2065 and 2071-2095) using an ensemble projection dataset. Methods and results: The analysis of heat requirements based on GDD from 1st of April to harvest date identified consistent maturity groups of the varieties studied, especially for indigenous Greek varieties. Trend analysis using the basic linear regression model showed that harvest dates have shifted earlier, during the last few decades, due to warmer conditions (especially during the ripening period) in most cases. In addition, trends in potential alcohol (acid) levels were found to be positively (negatively) correlated with maximum air temperatures in the majority of cases. Analysis of future projections using a global multi-climate model ensemble dataset (10 regional climate models) showed that harvest dates are projected to shift earlier up to 40 days in two future time periods (i.e., 2041-2065 and 2071-2095) depending on the variety and the emission pathway. Conclusions: Harvest dates of the early ripening varieties were associated more with the variations in maximum air temperatures during March to July, while mid- and late ripening varieties appeared to be affected more by maximum air temperatures during the ripening period. In addition, late ripening, mostly indigenous, varieties were less impacted by temperature increases compared to international varieties. Significance of the study: The indigenous Greek varieties appear better adapted to the recent and projected future climate of the region, responding less to warming as compared to international varieties in the majority of the study cases.

The purpose of this work was to study the response of two apple cultivars bred for low chilling environments to artificial chilling accumulation. Two trials were carried out; in experiment one, excised shoots were randomly taken from “Caricia” and “Princesa”, and in experiment two, intact and excised shoots of “Caricia”, “Princesa” and “Gala” (control) were collected. After collection, both shoot types were exposed to artificial chilling accumulation (4.0 ± 0.5°C) from 0 to 1200 chill units (CU). Bud break of mixed buds of “Caricia” and “Princesa” was higher than 50% between 0 CU to 1200 CU, irrespective of shoot type. Bud break of “Gala” mixed buds exceeded 50% only in intact shoots after accumulating 900 CU. The mean time to bud break of “Caricia” and “Princesa” diminished with increasing chilling accumulation and stabilized after ~600 CU, depending on the type of shoot and the year of experimentation. The low-chill apple cultivars tested in this work showed shallow dormancy, but they required moderate cold accumulation (800 – 1150 CU) to fully satisfy their chilling requirements. Thus, although their shallow dormancy makes them suitable for cultivation in chill-deficient environments, they cannot be considered low-chill cultivars.