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This study was carried out to estimate the annual chilling and heat accumulation in Kurdistan region-Iraq using three different models; chilling hours (CH), chilling units (CU) and chilling portions (CP), as well as estimating the accumulated growing degree hours (GDH) using the ChillR Package, Version 0.72.8 based on daily maxima and minima temperatures of 170 locations for 40 years (1983-2022) downloaded from NASA. The results showed that in Kurdistan region, the chilling hours with 7 classes ranged from 335 CH in Shahreban (Diyala) to 1083 CH in Amedi, Deraluk, Dinarte, Kani Masi, and Shiladize (Duhok), and Barzan (Erbil), with an average of 886 CH. The chilling units (CU, Utah Model) with 6 classes ranged from 507 CU (Shahreban, Diyala) to 1135 CU (Hizawa, Duhok), with an average of 927 CU. However, the chilling portions with 7 classes ranged from 30.0 CP in Shahreban to 58.3 CP in Ahmad Awa, Khurmal, Penjwin, Sirwan, and Zalm (Salaymaniyah), with an average of 49.5 CP. Growing degree hours with 7 classes ranged from 1136 GDH Choman, Galala, Haji Omaran and Samilan (Erbil) to 8564 GDH in Shahreban, with an average of 3256 GDH. All models were strongly correlated with location parameters, the highest strong correlations were found between each CP and GDH with AAT. The observations emphasized that both CU and CP models are more accurate than CH model for estimation of chilling and growing degree hours (units) in Kurdistan region-Iraq. [ABSTRACT FROM AUTHOR]

Determination of chilling and heat requirements is respected in the selection of the suitable cultivars for producers to avoid damages caused by an inadequate winter chilling in a certain area. It also play an important role within a breeding program, when selecting parents to get late or early flowering cultivars. The present study aimed to estimate the chilling and heat requirements of breaking bud dormancy for flowering and vegetative growth in three Iranian almond cultivars in an orchard located in the suburbs of Garmdarreh (32.45°N; 50.91°E; altitude 1960 m). The three almond cultivars had different flowering times, i.e. early: ʻMohebʼ, medium: ʻMamaieʼ and late: ʻRabiʼ. To provide adequate chilling, fourteen-year-old trees were exposed to low temperature treatments (4 ± 1 °C) to simulate 0–1500 h of chilling at 250 h intervals. The cultivars varied in their chilling and heat requirements in terms of chilling hours and growing degree hours, GDH, to achieve bud break for flowering, i.e. 'Moheb' (250 h and 2132 GDH), 'Mamaie' (500 h and 2460 GDH) and 'Rabi' (500 h and 2624 GDH). To achieve bud break for leaf growth, the late-leafing cultivar ('Rabi') required 750 chilling hours and a heat requirement of 3608 GDH. The earlier-leafing cultivars ('Moheb' and 'Mamaie') had lower heat requirements for leaf unfolding. Although 'Rabi' and 'Mamaie' had similar chilling requirements of 500 h, 'Rabi' required almost a week (168 h) of warm weather after chilling to achieve bud break. This implies that spring frost is rarely a problem for 'Rabi' in Iran. 'Moheb' was not suitable because of its low chilling and heat requirements, hence its inability to escape early spring frosts and late winter cold. [ABSTRACT FROM AUTHOR]

Apricot has undergone an important cultivar renewal during the last years in response to productive and commercial changes in the crop. The impact of the sharka disease (plum pox virus) prompted the release of cultivars resistant/tolerant to this virus, leading to a major cultivar renewal worldwide. This has caused high variability in chilling requirements on new releases that remain unknown in many cases. In many apricot-growing areas, the lack of winter chilling is becoming a limiting factor in recent years. To deal with this situation, growers must choose cultivars well adapted to their areas. However, the information available on the agroclimatic requirements of the cultivars is very limited. To fill this gap, in this work, we have characterized the chilling requirements of 13 new apricot cultivars from Europe (France, Greece and Spain) and North America (USA) in two experimental collections in Aragón (Spain). We established the chilling period using male meiosis as a biomarker for endodormancy release over two years. Chilling requirements ranged from 51.9 Chill Portions (CP) to 70.9 CP. Knowing the chilling requirements of cultivars will help growers to select suitable cultivars adapted to the chill availability of their region. [ABSTRACT FROM AUTHOR]

Like other temperate woody species, stone fruit trees (peach, nectarine, and apricot) must accumulate a specific amount of chilling during endodormancy and heat during eco dormancy for proper growth and development. Each cultivar has particular requirements, and special attention is needed to know them for an optimal decision support system. This paper aims to present the available information on the chilling- and heat requirements of peaches, nectarines, and apricots, focusing on the methods used for their determination. The results also reflected the necessity to standardize the methodology with the possibility of extending to new cultivars tested in different areas. [ABSTRACT FROM AUTHOR]

Climate change is a reality of the difficult period we are going through. Plant evolution is generally strongly correlated with variations in temperatures, precipitation, and solar radiation being affected by extreme events. Late frosts influence fruit production, the number of cold hours (perhaps insufficient in recent years), and winter windows in which very high temperatures occur and negatively influence the dormancy of some fruit-bearing species. Paw-paw (Asimina triloba L. Dunal) and jujube (Ziziphus jujuba Mill.) are new fruit species for Romanian areas more resilient to climate change. This paper aims to present the available information on this new fruit species' chilling and heat requirements, focusing on the methods used for their determination. The results reflected the scarcity of research on these fruit species and the necessity to have a methodology with the possibility to extend to new cultivars in different areas. [ABSTRACT FROM AUTHOR]

The change in the occurrence of phenophases in fruit trees gave a challenge to climate change. Changes in average temperatures and rainfall and increased short- and long-term extreme events are already affecting crop yields worldwide. To avoid possible losses, it is necessary to provide helpful information to farmers in real time regarding initiating a particular stage of fruit tree development. Modern breeding programs have launched cultivars with low winter chill requirements onto the market, involving extensive zoning research in recent years. Also, there are species/cultivars with a chilling requirement that can no longer be satisfied in some areas, leading to losses in production/economic inefficiency. Climate change generated significant interest in developing specific tools and models adjusted for each crop. The paper aims to present the available information on apple and pear trees' chilling and heat requirements, focusing on the methods used for their determination. The results reflect comparing the methods used and their efficacity for those species. [ABSTRACT FROM AUTHOR]

Flowering in temperate fruit trees depends on the temperatures during the previous months; chill is required to overcome endodormancy, and then heat exposure is needed. These agroclimatic requirements are cultivar-specific and determine their adaptability to the growing area and their response to climate change. We aim to estimate the agroclimatic requirements of 16 traditional cultivars of European pears grown in Zaragoza (Spain). We used Partial Least Squares regression analysis to relate 20-year records of flowering dates to the temperatures of the 8 previous months. This approach allowed us to establish the chilling and forcing periods, through which we quantified temperatures with three models for chill accumulation (Chilling Hours, Utah model, and Dynamic model) and one model for heat accumulation (Growing Degree Hours). The results indicated very little difference in the chilling and forcing periods. Chill requirements ranged from 43.9 to 49.2 Chill Portions; from 1027 to 1163 Chilling Units; and from 719 to 774 Chilling Hours. Heat requirements ranged from 6514 to 7509 Growing Degree Hours. Flowering dates were mainly determined by the temperatures during the chilling period. This means that reductions in winter chill caused by global warming in many regions could cause flowering delays or even failures in the fulfillment of chill requirements. [ABSTRACT FROM AUTHOR]

Organic peach production systems in Florida are an attractive option for farmers selling direct-to-consumer, including U-Pick operations. Profitability is contingent upon appropriate cultivar selection, efficient nutrient and water management, preventative pest management, and selling fruit for a price premium during the early market window. This comprehensive 14-page fact sheet includes evidence- and producer-based best practice recommendations and is designed for small- and mid-size farm operators who are certified organic or who desire to use organic practices. Written by David Campbell, Danielle Treadwell, Ali Sarkhosh, Oscar E. Liburd, and Jeff Brecht, and published by the UF/IFAS Horticultural Sciences Department. https://edis.ifas.ufl.edu/hs1447

Apricot has undergone an important cultivar renewal during the last years in response to productive and commercial changes in the crop. The impact of the sharka disease (plum pox virus) prompted the release of cultivars resistant/tolerant to this virus, leading to a major cultivar renewal worldwide. This has caused high variability in chilling requirements on new releases that remain unknown in many cases. In many apricot-growing areas, the lack of winter chilling is becoming a limiting factor in recent years. To deal with this situation, growers must choose cultivars well adapted to their areas. However, the information available on the agroclimatic requirements of the cultivars is very limited. To fill this gap, in this work, we have characterized the chilling requirements of 13 new apricot cultivars from Europe (France, Greece and Spain) and North America (USA) in two experimental collections in Aragón (Spain). We established the chilling period using male meiosis as a biomarker for endodormancy release over two years. Chilling requirements ranged from 51.9 Chill Portions (CP) to 70.9 CP. Knowing the chilling requirements of cultivars will help growers to select suitable cultivars adapted to the chill availability of their region.

Plant nursery production systems are a multi-billion-dollar, international, and horticultural industry that depends on storing and shipping live plants. The storage environment represents potentially desiccating and even fatal conditions for dormant, bareroot, and deciduous horticulture crops, like orchard trees, forestry trees, ornamental trees, and grapevines. When tree mortality is considered within a plant hydraulic framework, plants experiencing water stress are thought to ultimately die from hydraulic failure or carbon starvation. We hypothesized that the hydraulic framework can be applied to stored crops to determine if hydraulic failure or carbon starvation could be attributed to mortality. We used deciduous trees as model species because they are important horticultural crops and provide a diversity of hydraulic strategies. We selected cultivars from six genera: Acer, Amelanchier, Gleditsia, Gymnocladus, Malus, and Quercus. For each cultivar, we measured stem hydraulic conductance and vulnerability to embolism. On a weekly basis for 14 weeks (March–June), we removed trees of each cultivar from cold storage (1–2°C). Each week and for each cultivar, we measured stem water potential and water content (n = 7) and planted trees to track survival and growth (n = 10). At three times during this period, we also measured non-structural carbohydrates. Our results showed that for four cultivars (Acer, Amelanchier, Malus, and Quercus), the stem water potentials measured in trees removed from storage did not exceed stem P50, the water potential at which 50% of stem hydraulic conductivity is lost. This suggests that the water transport system remains intact during storage. For two cultivars (Gleditsia and Gymnocladus), the water potential measured on trees out of storage exceeded stem P50, yet planted trees from all weeks survived and grew. In the 14 weeks, there were no significant changes or directional trends in stem water potential, water content, or NSC for most cultivars, with a few exceptions. Overall, the results show that the trees did not experience detrimental water relations or carbon starvation thresholds. Our results suggest that many young deciduous trees are resilient to conditions caused by prolonged dormancy and validate the current storage methods. This experiment provides an example of how a mechanistically based understanding of physiological responses can inform cold storage regimes in nursery tree production.

Abstract The objective of this work was to evaluate the effect of heat waves on the bud dormancy of grapevines with contrasting chilling requirements. ‘Chardonnay’, ‘Merlot’ and ‘Cabernet Sauvignon’ hardwood cuttings were collected in vineyards of Veranópolis, State of Rio Grande do Sul, Brazil, and were exposed to constant (7.2°C) or alternate (7.2 and 18°C for 12/12 hours) temperatures, combined with zero, one or two days a week at 25°C. Periodically, part of cuttings was transferred to 25°C for daily budburst evaluation. Endodormancy (dormancy controlled by cold) was overcome with 150 chilling hours (CH) at 7.2ºC in ‘Chardonnay’, 300 CH in ‘Merlot’ and 400 CH in ‘Cabernet Sauvignon’. Daily temperature cycles ranging from7.2ºC to 18°C did not affect the endodormancy process. Heat waves of 25°C resulted in increase in CH to overcome endodormancy. The negative effect of heat waves depended on their duration, with heat partially canceling out the chilling accumulation after 36 continuous hours on the dormancy. Such evidence shows that the dormancy evolution is affected by the impact of the heat interspersed with cold, and should be considered in the adjustment and/or development of better-adapted models for the prediction of the budburst potential of the grapevine culture in Southern Brazil.

Plant nursery production systems are a multi-billion-dollar, international, and horticultural industry that depends on storing and shipping live plants. The storage environment represents potentially desiccating and even fatal conditions for dormant, bareroot, and deciduous horticulture crops, like orchard trees, forestry trees, ornamental trees, and grapevines. When tree mortality is considered within a plant hydraulic framework, plants experiencing water stress are thought to ultimately die from hydraulic failure or carbon starvation. We hypothesized that the hydraulic framework can be applied to stored crops to determine if hydraulic failure or carbon starvation could be attributed to mortality. We used deciduous trees as model species because they are important horticultural crops and provide a diversity of hydraulic strategies. We selected cultivars from six genera: Acer , Amelanchier , Gleditsia , Gymnocladus , Malus , and Quercus. For each cultivar, we measured stem hydraulic conductance and vulnerability to embolism. On a weekly basis for 14 weeks (March–June), we removed trees of each cultivar from cold storage (1–2°C). Each week and for each cultivar, we measured stem water potential and water content (n = 7) and planted trees to track survival and growth (n = 10). At three times during this period, we also measured non-structural carbohydrates. Our results showed that for four cultivars (Acer , Amelanchier , Malus, and Quercus), the stem water potentials measured in trees removed from storage did not exceed stem P 50, the water potential at which 50% of stem hydraulic conductivity is lost. This suggests that the water transport system remains intact during storage. For two cultivars (Gleditsia and Gymnocladus), the water potential measured on trees out of storage exceeded stem P 50, yet planted trees from all weeks survived and grew. In the 14 weeks, there were no significant changes or directional trends in stem water potential, water content, or NSC for most cultivars, with a few exceptions. Overall, the results show that the trees did not experience detrimental water relations or carbon starvation thresholds. Our results suggest that many young deciduous trees are resilient to conditions caused by prolonged dormancy and validate the current storage methods. This experiment provides an example of how a mechanistically based understanding of physiological responses can inform cold storage regimes in nursery tree production. [ABSTRACT FROM AUTHOR]

This study quantified the chilling requirements for the induction and overcoming of endodormancy (chilling-controlled physiological dormancy) of grapevines buds. Cuttings of the cultivars Chardonnay, Merlot and Cabernet Sauvignon were collected in vineyards in Veranópolis-RS in the winter period of 2019 and 2020. The cuttings were kept at a constant temperature of 7.2 °C or daily cycles of 7.2/18 °C for 6/18 h, 12/12 h or 18/6 h, up to 600 chilling hours (CH). Every 50 CH, part of the cuttings from each treatment was transferred to a temperature of 25 °C for daily assessment of the budburst in the green tip stage. The cultivars had different chilling requirements for inducing and overcoming endodormancy, reaching a total of 150 CH for 'Chardonnay', 300 CH for 'Merlot' and 400 CH for 'Cabernet Sauvignon'. Of these, 50 CH were required to induce endodormancy in cultivars Chardonnay and Merlot and 100 CH for cultivar Cabernet Sauvignon. Dormancy evolution did not differ between cultivars in response to thermal regimes, with a temperature of 18 °C inert to the accumulation of CH. Precocity and uniformity of budburst were higher after chilling requirements were met during endodormancy for each genotype. [ABSTRACT FROM AUTHOR]

Dormancy is important for the pear (Pyrus pyrifolia) to survive a harsh environment. The molecular base of dormancy in pear, especially in some local cultivars, is still unclear. Genome-wide transcriptome analysis in flower buds of cv. Huangli (an excellent local cultivar native to Guizhou mountain area in China) was conducted to explore the mechanism regulating bud dormancy in pear. For the release of endo-dormancy 223 chilling hours (CHs) was needed in Huangli flower buds, which was less than in commercial cultivars. Comparisons of transcript amounts among seven dates during dormancy (30 Oct. vs. 15 Nov., 15 Nov. vs. 30 Nov., 30 Nov. vs. 15 Dec., 15 Dec. vs. 30 Dec., 30 Dec. vs. 15 Jan., and 15 Jan vs. 15 Feb.), resulted in the detection of 1 064, 1 057, 541, 412, 577, and 3 814 differentially expressed transcripts, respectively. The reference genome of pear was used to align the RNA-Seq reads and to measure the transcript expression. Gene ontology (GO) and Kyoto encyclopedia of genes and genomes (KEGG) were then used to annotate the transcript descriptions and to assign a pathway to each transcript. The results revealed, that secondary metabolite biosynthesis, especially phenylpropanoid biosynthesis pathway, was the most enriched pathway out of 132 pathways. These interesting results indicated that dormancy in Huangli might be regulated mainly by secondary metabolite biosynthesis pathway, and the two continuous dormant stages (endo-dormancy and eco-dormancy) might be regulated specifically by phenylpropanoid biosynthesis and plant hormone signal transduction, respectively.

Adequate chill is of great importance for successful production of deciduous fruit trees. However, temperate fruit trees grown under tropical and subtropical regions may face insufficient winter chill, which has a crucial role in dormancy and productivity. The objective of this review is to discuss the challenges for dormancy and chilling requirements of temperate fruit trees, especially in warm winter regions, under climate change conditions. After defining climate change and dormancy, the effects of climate change on various parameters of temperate fruit trees are described. Then, dormancy breaking chemicals and organic compounds, as well as some aspects of the mechanism of dormancy breaking, are demonstrated. After this, the relationships between dormancy and chilling requirements are delineated and challenging aspects of chilling requirements in climate change conditions and in warm winter environments are demonstrated. Experts have sought to develop models for estimating chilling requirements and dormancy breaking in order to improve the adaption of temperate fruit trees under tropical and subtropical environments. Some of these models and their uses are described in the final section of this review. In conclusion, global warming has led to chill deficit during winter, which may become a limiting factor in the near future for the growth of temperate fruit trees in the tropics and subtropics. With the increasing rate of climate change, improvements in some managing tools (e.g., discovering new, more effective dormancy breaking organic compounds; breeding new, climate-smart cultivars in order to solve problems associated with dormancy and chilling requirements; and improving dormancy and chilling forecasting models) have the potential to solve the challenges of dormancy and chilling requirements for temperate fruit tree production in warm winter fruit tree growing regions. [ABSTRACT FROM AUTHOR]

Many fruit and nut trees must fulfill a chilling requirement to break their winter dormancy and resume normal growth in spring. Several models exist for quantifying winter chill, and growers and researchers often tacitly assume that the choice of model is not important and estimates of species chilling requirements are valid across growing regions. To test this assumption, Safe Winter Chill (the amount of winter chill that is exceeded in 90% of years) was calculated for 5,078 weather stations around the world, using the Dynamic Model [in Chill Portions (CP)], the Chilling Hours (CH) Model and the Utah Model [Utah Chill Units (UCU)]. Distributions of the ratios between different winter chill metrics were mapped on a global scale. These ratios should be constant if the models were strictly proportional. Ratios between winter chill metrics varied substantially, with the CH/CP ratio ranging between 0 and 34, the UCU/CP ratio between -155 and +20 and the UCU/CH ratio between -10 and +5. The models are thus not proportional, and chilling requirements determined in a given location may not be valid elsewhere. The Utah Model produced negative winter chill totals in many Subtropical regions, where it does not seem to be useful. Mean annual temperature and daily temperature range influenced all winter chill ratios, but explained only between 12 and 27% of the variation. Data on chilling requirements should always be amended with information on the location and experimental conditions of the study in which they were determined, ideally including site-specific conversion factors between winter chill models. This would greatly facilitate the transfer of such information across growing regions, and help prepare growers for the impact of climate change.

Chilling accumulation in dormancy period for deciduous fruit tree is of very high importance. Failure to meet this chilling requirement reduces the performance and results in the loss of resources. In order to investigate the Chilling accumulation pattern in the cold regions of Iran, three-hour temperature data from 1985 to 2013 from 28 synoptic weather stations has been used. The three-hour synoptic temperature data for the dormancy period from November to March has been converted into an hourly temperature database with 3252800 numbers of records for each model has been calculated. Chilling Hours (CH), chilling units (Utah), and Dynamic (CP) models were used to determine the chilling accumulation. Chilling accumulation pattern based on CH model output from 775 to 1445 hours and based on Utah model from 1191 to 2121 chilling unit and also based on CP model from 63 to 96 chilling part between the cold region stations is variable. The elevation factor in chilling accumulation pattern in each of models has show the important role. In past decades, the frequency of chilling accumulation maximum was more than recent decades. The investigation of time series showed that there is a significant downward trend of chilling accumulation at the level of 0.05 in stations of Isfahan and Shahr-e Kurd and trend negative slope in most stations. Based on the validation criteria, Dynamic model output with a smaller RMSE shows a higher efficacy, compared to other models, to determine the chilling accumulation.

To quantify the effects of climate change on fruit production in Germany, this study aimed at determining long-term trends in winter chill, as calculated with the Chilling Hours and Dynamic Models (Chill Portions). An idealized daily temperature curve was used to convert daily temperature records from 43 weather stations, taken throughout the twentieth and late nineteenth centuries, into an hourly dataset, which was then converted to units of winter chill. Besides exposing temporal trends in winter chill, the data could be spatially interpolated, yielding contiguous maps of typical winter chill in Germany around 2010, as well as chilling losses since 1950.Throughout Germany, winter chill varied between 1700 and 3000 Chilling Hours or 125 and 150 Chill Portions. The areas of highest winter chill were located in the northern parts of the country. For the whole of Germany, there were no significant temporal trends.The extent of interregional variation in winter chill depended on the chilling model used. While the Chilling Hours Model showed strong declines in winter chill for the areas around Dresden and Leipzig, as well as for the Lake Constance region, the Dynamic Model did not detect such dramatic changes.More than a decline in winter chill, increased heat during the winter months might become a challenge to German fruit growers. As already experienced during the extraordinarily warm winter of 2006/07, warm temperatures during the winter can cause fruit trees that fulfill their chilling requirements relatively early to bloom prematurely. This can then lead to elevated risk of frost damage and hamper the homogeneity of flowering.

Phenology, pollen synchronization and fruit characteristics were studied during the season 2011-2012 for European hazelnut (Corylus avellana L.) cv. "Tonda di Giffoni" and three of its pollinizers ("Tonda Romana", "Tonda Gentile delle Langhe" and "Barcelona") in three agro-ecological conditions of central Chile. Male and female blooms occurred from June through August, with a flowering span ranging between two to two and a half months depending on the cultivar, pollinizer and study sites. "Tonda di Giffoni" male flowering onset occurred during the first week of June, up to two weeks earlier than female flowers (271 to 417 chilling hours) showing a marked protandrus dichogamy. "Tonda Gentile delle Langhe" and "Barcelona" pollinizers completely covered the female flowering period of "Tonda di Giffoni", while "Tonda Romana" fail to cover the first flowering week. In general, starting dates for the different phenological stages were directly and significantly (P

Dormancy is important for the pear (Pyrus pyrifolia) to survive a harsh environment. The molecular base of dormancy in pear, especially in some local cultivars, is still unclear. Genome-wide transcriptome analysis in flower buds of cv. Huangli (an excellent local cultivar native to Guizhou mountain area in China) was conducted to explore the mechanism regulating bud dormancy in pear. For the release of endo-dormancy 223 chilling hours (CHs) was needed in Huangli flower buds, which was less than in commercial cultivars. Comparisons of transcript amounts among seven dates during dormancy (30 Oct. vs. 15 Nov., 15 Nov. vs. 30 Nov., 30 Nov. vs. 15 Dec., 15 Dec. vs. 30 Dec., 30 Dec. vs. 15 Jan., and 15 Jan vs. 15 Feb.), resulted in the detection of 1 064, 1 057, 541, 412, 577, and 3 814 differentially expressed transcripts, respectively. The reference genome of pear was used to align the RNA-Seq reads and to measure the transcript expression. Gene ontology (GO) and Kyoto encyclopedia of genes and genomes (KEGG) were then used to annotate the transcript descriptions and to assign a pathway to each transcript. The results revealed, that secondary metabolite biosynthesis, especially phenylpropanoid biosynthesis pathway, was the most enriched pathway out of 132 pathways. These interesting results indicated that dormancy in Huangli might be regulated mainly by secondary metabolite biosynthesis pathway, and the two continuous dormant stages (endo-dormancy and eco-dormancy) might be regulated specifically by phenylpropanoid biosynthesis and plant hormone signal transduction, respectively. [ABSTRACT FROM AUTHOR]

Several studies reported the beneficial effect of Dormex (Hydrogen Cyanamid) on compensating the lack of chilling hours required for a normal vines budburst. It was recently prohibited in many countries due to its toxicity on plants and humans. The objective of this study was to find alternatives for Dormex. Gibberellic acid plays a role as endogenous hormone on budburst. Nano-fertilizers (Amino25) are known to prevent biotic and abiotic stresses in plant. No studies were conducted on the effect of both products on vines in warm winter climate. Two experiments will be discussed in this paper and compared to previous result of Dormex applied at the same location. The treatments were: Openfield /Without Products, Greenhouse/Without Products, Open-field!Gibberellic acid, Greenhouse/Gibberellic acid, Open-field/Amino25 and Greenhouse/ Amino25. The study was conducted on three ARRA seedless cultivars. Gibberllic acid was applied at 2ppm and Amino25 were applied at 1.5 g L- 1 for several times before budburst. Giberellic acid enhanced bud formation under greenhouse as Dormex did and induced earliness of 2 weeks in budburst while its effect on fruits, flowers and yield was less efficient than Dormex. It did not have effect in open-field conditions as well as Amino25 in both cultivation systems. Gibberellic acid could replace Dormex to resolve bud burst problem. Since Gibberellic acid and Nano-fertilizers are non-toxic and could be used on organic farming, advanced research should take place to enhance the effects of Gibberellic acid in open-field conditions and additional studies are recommended regarding the effect of Nanofertilizers on grapevines. [ABSTRACT FROM AUTHOR]

Phenology, pollen synchronization and fruit characteristics were studied during the season 2011-2012 for European hazelnut (Corylus avellana L.) cv. "Tonda di Giffoni" and three of its pollinizers ("Tonda Romana", "Tonda Gentile delle Langhe" and "Barcelona") in three agro-ecological conditions of central Chile. Male and female blooms occurred from June through August, with a flowering span ranging between two to two and a half months depending on the cultivar, pollinizer and study sites. "Tonda di Giffoni" male flowering onset occurred during the first week of June, up to two weeks earlier than female flowers (271 to 417 chilling hours) showing a marked protandrus dichogamy. "Tonda Gentile delle Langhe" and "Barcelona" pollinizers completely covered the female flowering period of "Tonda di Giffoni", while "Tonda Romana" fail to cover the first flowering week. In general, starting dates for the different phenological stages were directly and significantly (P<0.05) correlated with chilling hour accumulation and growing degree days. Fruit set (34.1%) and maximum fruit diameter (16.6 mm) were significantly lower in the case of "Tonda Gentile delle Langhe" compared to "Tonda Romana" (82.2%, 17.3 mm) and "Barcelona" (74.7%, 17.4 mm). [ABSTRACT FROM AUTHOR]

The purpose of this study was assessing the impacts of different chilling periods on the release of dormancy in walnut lateral buds, carbohydrates metabolism, phenol compounds content, and activities of soluble and cell wall peroxidase and polyphenol oxidase. In this line, one-year-old shoots were collected randomly from ten-year-old trees of Ziyarat village (Gorgan) in defoliation which were then cut into 9 cm pieces each with a single lateral bud and were subjected to different chilling treatments (0, 700, 1400 hour) at 4±1 °C and then forcing condition (25 ± 2 ◦C, 12 h light:12 h dark photoperiod, 20 µmol m−2 s−1). Results showed that 700 and 1400 chilling hours significantly increased percentage and rate of walnut lateral bud dormancy release and decreased time of initiation bud break in comparison with control. Chilling caused starch and non-reducing sugar degradation and resulted in the increase of reducing sugars. This had a positive significant relationship with the percentage of bud dormancy release. Phenols content, soluble and cell wall peroxidase activities increased up to 700 hour chilling while polyphenol oxidase activity increased up to 1400 hour as compared with control. It seems that the buildup of reducing sugars provides the required energy for dormancy release, and the increase of phenols and soluble and cell wall peroxidase activities result in decrease of oxidative stress and development of cold tolerance in buds. Moreover, rising polyphenol oxidase activity caused removing phenolic inhibitors and/or synthesis of antioxidant phenols. These processes in parallel promoted dormancy release of Persian walnut lateral buds.

Stone fruit trees of genus Prunus, like other temperate woody species, need to accumulate a cultivar-specific amount of chilling during endodormancy, and of heat during ecodormancy to flower properly in spring. Knowing the requirements of a cultivar can be critical in determining if it can be adapted to a particular area. Growers can use this information to anticipate the future performance of their orchards and the adaptation of new cultivars to their region. In this work, the available information on chilling- and heat-requirements of almond, apricot, plum, peach, and sweet cherry cultivars is reviewed. We pay special attention to the method used for the determination of breaking dormancy, the method used to quantify chilling and heat temperatures, and the place where experiments were conducted. The results reveal different gaps in the information available, both in the lack of information of cultivars with unknown requirements and in the methodologies used. The main emerging challenges are the standardization of the conditions of each methodology and the search for biological markers for dormancy. These will help to deal with the growing number of new cultivars and the reduction of winter cold in many areas due to global warming.

This 6-page document provides basic information and guidelines on water requirements and irrigation strategies for peaches grown in Florida. Written by C. Zambrano-Vaca, L. Zotarelli, K. Migliaccio, R. Beeson Jr., K. Morgan, J. Chaparro, and M. Olmstead and published by the UF/IFAS Horticultural Sciences Department, April 2018. http://edis.ifas.ufl.edu/hs1316

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ABSTRACT: Evaluation of yield performance is important to find the most adapted blueberry cultivars in a particular region. This research aimed to evaluate the flowering and hasvesting periods, the production per plant, and fruit quality of eight rabbiteye blueberry cultivars (Aliceblue, Bluebelle, Bluegem, Briteblue, Climax, Delite, Powderblue, and Woodard) and two highbush blueberries (Georgiagem and O’Neal), in mild winter conditions in Pinhais-PR. Flowering and harvesting periods, production, berry weight, size, pH, soluble solids, titratable acidity, ratio and color of the fruits were evaluated in the 2013/2014 and 2014/2015 growing seasons, when the plants had two and three years old, respectively. Cultivars flowered from August to September, and harvest was concentrated in November and December. Berry weight, size, pH, soluble solids and acidity varied among the cultivars. The average ratios of 14.97 and 13.39 for each crop proved that the cultivars have good fruit quality. There was little variation in fruit color in the two years evaluated. Blueberry cultivars showed the staining characteristics and physical and chemical attributes of quality compatible to blueberry from other traditional regions. Under mild winter conditions, young plants of rabbiteye blueberry cultivars, Climax, Delite, Bluegem and Powderblue, are the most productive, while the highbusch cultivars bear few fruits.

Rootstock-planting forcing culture was developed in asparagus to harvest spears even during the seasons when the plants become dormant, but the demand for them high. In this study, cumulative hours during which the air temperature remained lower than 5°C, i.e. chilling hours (CHs), were calculated to determine dormancy breakage for asparagus cultures. We also measured CIELab colour values for cut stems immediately before rootstock digging, and determined whether they could be substituted and/or compensated for CHs while evaluating asparagus plant productivity in different low-temperature backgrounds, and obtained regression equations for yield estimation. Asparagus seedlings were cultivated in seven different regions across Japan and brought to the study site for harvesting. Our regression equation based on CHs and rootstock weight for yield estimation had relatively high fitness (adjusted R2 = 0.5795). The colour values of cut stalks at rootstock digging can also be used to evaluate their productivity. These values can be useful in regions where CHs cannot be determined, although their effectiveness was slightly lower than that of CHs of areas adjacent to the study sites. [ABSTRACT FROM PUBLISHER]

O pessegueiro e a nectarineira são culturas com grande potencial climático e de mercado, mas ainda pouco exploradas no Estado do Paraná. O objetivo deste trabalho foi indicar zonas de menor risco climático para produção dessas culturas no Estado do Paraná, utilizando informações climáticas e agronômicas. Para tanto, foram usados dados históricos de 32 estações meteorológicas do IAPAR, para estimar e mapear os riscos de geadas tardias e o total médio de horas de frio (hf) abaixo de 7,2ºC no período maio-setembro. As regiões em que a última geada ocorre antes da fase de floração e com número de horas de frio adequado às exigências das variedades, foram consideradas aptas. Grande parte do norte, oeste e litoral do Paraná não apresenta horas de frio suficientes para as espécies. As áreas localizadas ao sul, com altitudes acima de 800 m, são as mais adequadas. Dentro da área apta, foram classificadas oito zonas, de acordo com a necessidade de frio das variedades de pessegueiro e nectarineira, e a característica de cada região: zona 1 (75 a 150 hf); zona 2 (150 a 200 hf); zona 3 (200 a 250 hf); zona 4 (250 a 300 hf); zona 5 (300 a 350 hf); zona 6 (350 a 400 hf), zona 7 (400 a 450 hf) e zona 8 (> 450 hf). As zonas de menor altitude acumulam menos horas de frio e são recomendadas para variedades com menor necessidade de frio. As zonas de maior altitude, que se apresentam com temperaturas mais baixas, têm maior somatório de horas de frio e são recomendadas para variedades com maior necessidade de frio (> 400 horas de frio). A última geada severa provável ocorre no final de agosto, nas regiões mais frias, e não prejudica a floração do pessegueiro e nectarineira. Os resultados obtidos neste estudo possibilitam a adoção de políticas de incentivo a essas culturas com baixo nível de risco, no Estado do Paraná.Peach and nectarine crops, despite their high climatic and market potential, are not yet well exploited in the state of Paraná. The objective of this research was to indicate zones with lower climatic risk for production of these crops in the state of Paraná, Brazil, using climatic risk analysis and agronomic data. Historical data of 32 weather stations of IAPAR were analyzed to estimate and map the risks of late frost and the average totals of chilling hours above 7.2ºC accumulated from May to September. The regions in which the last frost occurs before flowering and with the total chilling hours suitable to the cultivars needs were considered apt. Most of the north, west and the coast of Paraná do not have enough chilling hours. The areas located in the south with altitudes above 800 m are the most suitable. Within the apt areas eight zones were classified according to the chilling requirements of peaches and nectarine varieties and climatic conditions of each region: zone 1 (75 to 150 hf); zone 2 (150 to 200 hf); zone 3 (200 to 250 hf); zone 4 (250 to 300 hf); zone 5 (300 to 350 hf); zone 6 (350 to 400 hf), zone 7 (400 to 450 hf) and zone 8 (> 450 hf). The zones with lower altitude and higher temperatures accumulate less chilling hours from May to September and are indicated for cultivars with lower chilling requirement. The zones with higher altitudes and high chilling accumulation are suitable for varieties with high chilling requirements (> 400 chilling hours). The last frost is likely to occur in the last ten days of August in the colder regions and do not cause damages to suitable varieties of peaches and nectarine. The results obtained in this work support the adoption of policies to foment these crops in the state of Paraná with low risk.

Algumas cultivares de pereira asiática, quando plantadas em regiões onde ocorrem invernos com baixo número de horas de frio, comumente apresentam deficiência e desuniformidade na brotação e floração, necessitando de meios artificiais para a quebra de dormência. Visando a miminizar esse problema, foi instalado um experimento num pomar de 4 anos de pereiras 'Hosui' (Pyrus pyrifolia), em espaçamento 4,0m x 4,0m, na Estação Experimental do Canguiri-da Universidade Federal do Paraná, no município de Pinhais-PR (latitude 25º25' sul, longitude 49º08' e altitude 920m), onde a soma de horas de frio atingiu 141 horas abaixo de 7,2ºC durante o inverno de 2005. Os tratamentos foram aplicados quando as plantas estavam no estádio fenológico A1 (gema inchada), sendo o experimento realizado em delineamento inteiramente ao acaso, com 4 repetições, em esquema fatorial 2x4x7, onde foram testados dois tipos de condução, em taça e em líder central modificado, três concentrações de óleo mineral a 4%, 6% e 8%, e uma testemunha, durante o período de agosto a novembro de 2005, e sete avaliações realizadas semanalmente pelo número de gemas em início de brotação, gemas brotadas e gemas mortas, em 4 ramos de um ano de idade e em posição inclinada, previamente marcados por planta. Os resultados obtidos mostraram que a aplicação de óleo mineral, nas concentrações de 4%, 6% e 8%, anteciparam a brotação de gemas em relação à testemunha e aumentaram a porcentagem de gemas brotadas nos dois tipos de condução, sendo que as concentrações de 6% e 8% foram mais efetivas para antecipar a brotação do que a de 4%. A porcentagem de gemas brotadas aos 84 dias após a aplicação do óleo mineral não diferiu entre os sistemas de condução, em líder central modificado e em taça.Some Asian pear cultivars, if cultivated in regions where less chilling hours are accumulated during winter, may present uneven budding and blooming and hence, need to have their dormancy broken by artificial means. In order to minimize such problem, an experiment was conducted in a 4-year-old 'Hosui' pear (Pyrus pyrifolia) with 4.0 x 4.0m tree spacing orchard, at the Canguiri Station, in Pinhais-PR (latitude 25º25'S, longitude 49º08' and altitude of 920m), pertaining to the Federal University of Parana, in which accumulation of 141 chilling hours under 7.2ºC was reached during the 2005 winter. Treatments were applied when plants were at the A1 phenological stage (bud swelling), using a completely randomized factorial design with 4 replications in a 2x4x7 factorial scheme in which two types of tree training, vase or central leader, three mineral oil concentrations, 4, 6 or 8%, and a control applied from August to November 2005, and seven weekly performed evaluations based on the number of buds at pre-budding stage as well as broken and dead buds in four previously selected horizontally inclined 1-year-old stems per tree were tested. Obtained results showed that application of mineral oil at 4, 6 and 8% anticipated bud break compared to the control and enhanced bud break percentage in both training systems, being the concentrations of 6% and 8% more effective in anticipating bud break than 4%. The percentage of bud break at the 84th day after mineral oil application did not differ between the two training systems, i.e. vase and central leader.

The objective of this study was to evaluate the duration of phenological stages of ‘Tupy’ and ‘Xavante’ blackberries grown under subtropical conditions with the goal of optimizing the production system. The experiment was conducted at the Experimental Station, Agricultural Research Center, Londrina State University, PR, Brazil, during two consecutive seasons: 2013 and 2014. A completely randomized design was used with five plot replications, with each composed of five plants. The duration (in days) of each phenological stage was recorded for both cultivars through visual observations at the following times: the onset of bud sprouting, the onset of flowering, the onset of fruit maturation, the beginning of fruit harvest, the end of flowering, and the end of fruit harvest. The duration (in days) of the following fruit development stages was also recorded: flower bud, full open flower, unripe green berry, ripening pink berry, and ripe berry. The phenological development of ‘Tupy’ and ‘Xavante’ blackberries was directly influenced by the subtropical winter conditions with changes in bud sprouting, flowering and fruit harvesting periods. In the 2013 season, ‘Tupy’ had a later start of the growth cycle than ‘Xavante’, but fruit harvest for both ended at the same time in early summer. In the 2014 season, ‘Xavante’ maintained its characteristic early start, and ‘Tupy’ also resumed the growth cycle, which was earlier than the previous season. The duration of fruit development was similar for both cultivars. ‘Tupy’ and ‘Xavante’ grown in subtropical mild winter conditions demonstrated unique phenology, with earlier and shorter growth cycles than in temperate regions; thus, growing blackberries as two annual crops to optimize the production system is proposed. [ABSTRACT FROM AUTHOR]

Foram traçadas as cartas da distribuição de disponibilidade de horas de frio na região Central do Rio Grande do Sul. Para tal, utilizaram-se os dados de disponibilidade de ocorrência do número médio acumulado de horas de frio Maps of chilling hours distribution in the central region of Rio Grande do Sul, Brazil, were drawn. Mean of chilling hours bellow 7°C (HF

Determinaram-se as disponibilidades de horas de frio abaixo de 7°C (HFThe availability of chilling hours below 7°C (HF

A methodology is proposed to identify the coldest areas of the island of Mallorca through satellite-derived surface temperatures. Land-surface temperatures from the Meteosat Second Generation (MSG-LST) just before sunrise for 1 year starting on September 1, 2007, were used. Fields for situations with clear skies and weak wind nights were selected, corresponding to 173 days of the year under study. Under these conditions, cold pools were generated in the centre of the three main basins of the island, in agreement with previous numerical and climatological studies. Maps of minimum air temperature and chilling hours, averaged over a season or annually, were obtained from the MSG-LST fields. These maps were then associated with the requirements of actual crop distributions. [ABSTRACT FROM AUTHOR]

Abstract: Temperate fruit and nut species require exposure to chilling conditions in winter to break dormancy and produce high yields. Adequate winter chill is an important site characteristic for commercial orchard operations, and quantifying chill is crucial for orchard management. Climate change may impact winter chill. With a view to adapting orchards to climate change, this review assesses the state of knowledge in modelling winter chill and the performance of various modelling approaches. It then goes on to present assessments of past and projected future changes in winter chill for fruit growing regions and discusses potential adaptation strategies. Some of the most common approaches to modelling chill, in particular the Chilling Hours approach, are very sensitive to temperature increases, and have also been found to perform poorly, especially in warm growing regions. The Dynamic Model offers a more complex but also more accurate alternative, and use of this model is recommended. Chill changes projected with the Dynamic Model are typically much less severe than those estimated with other models. Nevertheless, projections of future chill consistently indicate substantial losses for the warmest growing regions, while temperate regions will experience relatively little change, and cold regions may even see chill increases. Growers can adapt to lower chill by introducing low-chill cultivars, by influencing orchard microclimates and by applying rest-breaking chemicals. Given substantial knowledge gaps in tree dormancy, accurate models are still a long way off. Since timely adaptation is essential for growers of long-lived high-value perennials, alternative ways of adaptation planning are needed. Climate analogues, which are present-day manifestations of future projected climates, can be used for identifying and testing future-adapted species and cultivars. Horticultural researchers and practitioners should work towards the development and widespread adoption of better chill accumulation and dormancy models, for facilitating quantitatively appropriate adaptation planning. [Copyright &y& Elsevier]

Abstract: Many fruit and nut species require cold temperatures during the dormancy season to initiate flowering and bear fruit. Quantifying these chilling requirements is crucial for identifying appropriate cultivars for a given site, for timing applications of rest-breaking chemicals and for predicting consequences of climate change. We present a new method to test temperature models describing chilling and heat requirements of perennial plants, and use this method to compare the ability of four chilling models (Chilling Hours, Utah Model, Positive Utah Model and Dynamic Model) to explain walnut phenology in California. When plotting remaining heat before a phenological stage is reached against accumulated winter chill, observational curves for all years should intersect in one common point, assuming fixed chilling and heat requirements and a sequential fulfillment of these requirements. This point defines the chilling and forcing requirements of the plant, and the quality of the chilling/heat model combination is indicated by how well defined the intersection point is. We used this method on a total of 1297 phenological observations, including four walnut cultivars, seven phenological stages and eight locations in California. Using an hourly temperature record, winter chill was quantified by the four chilling models and remaining heat was estimated using the Growing Degree Hour concept. The theoretical intersection point was more clearly defined for the Dynamic and Positive Utah Models than for the Chilling Hours and Utah Models in almost all cases, indicating that these are superior in explaining walnut phenology. It was also apparent that chilling models were not equivalent and that chilling requirements determined under constant temperature conditions, when quantified in Chilling Hours, were not representative of chilling requirements in orchards. [Copyright &y& Elsevier]

Abstract: Many fruit and nut crops require cold temperatures in winter to break dormancy. Quantifying this chilling requirement and selecting appropriate cultivars for the climate of a growing region is crucial for successful cultivation of such crops. Several models exist to quantify winter chill, and each growing region uses a model that has been shown to perform well under local climatic conditions. We tested the sensitivity of four commonly used chilling models to projected climatic change likely to affect fruit and nut production in the near future. For six sites in California''s Central Valley, we generated 100 years of synthetic hourly weather records, representing climatic conditions in 1950, 2000 and projected temperatures in 2041–2060 derived from three IPCC-AR4 General Circulation Models (GCMs; CSIRO, HadCM3 and MIROC; A2 greenhouse gas emissions scenario). Mean winter chill for each site and year was calculated using the Chilling Hours, Utah, Positive Utah and Dynamic models. All chilling models predicted substantial decreases in winter chill at all sites, but the extent of these decreases varied depending on the model used. Across all sites between 1950 and 2050, mean chilling was predicted to decrease by 33% (Chilling Hours), 26% (Utah Model), 16% (Dynamic Model) and 14% (Positive Utah Model). Research efforts are needed to identify the most appropriate chilling model for preparing fruit and nut growers for the imminent effects of climate change. [Copyright &y& Elsevier]

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The timing of pollen appearance in the atmosphere provides a general idea of the flowering onset of plants over a wide area. Woody plants in temperate regions have evolved mechanisms to preserve cells from the risk of frost during adverse weather conditions in the period prior to flowering regulated mainly by temperature. A number of indices have been developed to quantify the rest and heat requirements of temperature, which will enable the plant to adapt to environmental conditions. However, flowering is a dynamic and complex phenomenon and it is difficult to separate individual effects of different meteorological parameters. The use of modified bioclimatic indices could be a major step forward. In this study the Alnus glutinosa flowering in four different areas in north-western Spain in the period 1995-2003 is examined, and trends identified by means of information gathered by Hirst pollen traps. Temperature plays an important role in the maturation of reproductive organs and pollen production. Comparison with bioclimatic indices showed that temperature during the 25-55 days preceding pollen release was the main controlling factor, and that relationship between flowering time and bioclimatic indicator values differs according to local conditions. In colder areas, rest and heat temperature requirements are greater because the trees need protection over a longer period; in the Mediterranean region of north-western Spain, the rest temperature requirement and the threshold temperature are both higher than in Eurosiberian areas. Ombrothermic, Continentality and Thermicity indices are thus useful tools for characterizing the various bioclimatic areas of north-western Spain. [ABSTRACT FROM AUTHOR]

Slash pine ( Pinus elliottii Engelm.) seedlings were subjected to three wrenching treatments: One root wrenching in early August; Three root wrenchings in early August, September, and October; and No wrenchings. Seedlings were then lifted on five dates between November and February based on the number of chilling hours accumulated. All wrenched seedlings had reduced shoot dry weight, smaller shoot-root ratio, and smaller stem diameter and height. These morphological differences translated into improved survival as well as increased diameter and height growth when measured one and two years after planting. Only seedlings wrenched three times demonstrated improved root fibrosity. Furthermore, only multiple wrenched stock showed greater resistance to drying imposed prior to planting. At the time of lifting, seedlings lifted latest had greater stem diameter, increased root dry weight and number of root tips, and improved shoot-root ratio. However, no survival differences were detected across lifts, and those seedlings lifted earliest demonstrated the best height and diameter growth. [ABSTRACT FROM AUTHOR]