Percent Budbreak Research Articles

Appraisal of extended cane length and fruit thinning strategies on the performance of growth yield and quality of kiwifruit

The kiwifruit has been identified as an enormous fruit for mid-hill horticulture due to its wider adaptability and diversification. The size and quality of kiwifruit were affected by its market. As a result, appropriate canopy management and orchard techniques are key components in its production. Pruning and hand thinning, especially in kiwifruit, have been observed to improve the size and quality of the fruit. Traditional pruning maintained shorter canes with 6–12 nodes and 4 fruits/shoots. However, this study extended cane length and retained loads of 20 nodes/cane and 6 fruits/shoot. Considering the above, a study was conducted to determine the effects of extended cane length and fruit thinning on kiwifruit growth, yield, and fruiting performance. Five pruning levels have been employed: 8, 10, 12, 14, and 16 nodes/cane; 4, 6, and 8 fruits/fruiting shoot. The result revealed that the pruning of up to 12 nodes/cane coupled with thinning up to 6 fruits/fruiting shoot resulted in maximum cane diameter, leaf area, leaf: fruit ratio, advancement in flower initiation, bud break percentage (86.79 %), real fertility index, fruit yield and a proportion of grade “A" fruits. The highest leaf chlorophyll content (67.50), flowers per floral shoot, and productivity were recorded with pruning up to 16 nodes/cane coupled with thinning up to 6 fruits/fruiting shoot. The physico-chemical parameters such as fruit weight, diameter, volume, TSS, TSS: acid ratio, total sugars, and C: N ratio of the leaf and shoot were also found to be highest with pruning up to 12 nodes/cane coupled with thinning up to 6 fruits/fruiting shoot. This treatment also gave the maximum net return on a per-hectare basis, hence it was found to be the most profitable for the farmers.

Alternative products in the budbreak of ‘eva rubi’ apple trees under subtropical climate conditions

The apple tree requires chilling accumulation for budbreak. In locals where the chill accumalition is insufficient, chemical promoters are used to induce uniform budburst. However, alternatives that minimize damage to the environment and applicator have been sought. Thus, the aim of this work was to evaluate the efficiency of hydrogen peroxide, pau-d'alho hydrolate, lime sulphur and neem oil in inducing budbreak of ‘Eva Rubi’ apple tree in agroecological cultivation. Different concentrations (0%, 5%, 10%, 15% and 20%) of pau-d'alho hydrolate and hydrogen peroxide were tested in Palmas and Pato Branco. Three additionals treatments were added in the Lapa region, where mineral oil 3%, Dormex 0.5%, and Dormex 0.5% + 3% mineral oil were applied. In 2023, a new experiment was carried out only in Pato Branco, repeating the same concentrations of pau d'alho hydrolate and including new treatments with lime sulphur (1, 2, 3 and 4%) associated with 3% Neem oil. Percentage of budbreak, fruit set, productivity, and fruit mass were evaluated. The treatments showed no difference in the analyzed variables for Pato Branco and Palmas. In Lapa, there was an improvement in the percentage of budbreak in the plants treated with 15% ‘pau d'alho’ hydrolate, but still insufficient to state that this product can be used as budbreak inducer, however it suggests potential use, requiring, for that, the continuity of research in other species and experimental conditions. No phytotoxic effect was observed for hydrogen peroxide and ‘Pau d’alho’ hydrolate at the studied dosages.

Effect of BA on Bud Grafting in Grapefruit

Experiments were conducted at Shambat Research Station,Agricultural Research Corporation, Khartoum North, to test the effect ofconcentrations and application methods of benzyladenine (BA), as a pre-budding treatment, on scion bud-break and shoot elongation of grapefruit(Citrus paradisi Macf. cv. “Redblush”). Nine- to twelve- months old sourorange (Citrus aurantium L.) seedlings were used as rootstock. Twoapplication methods of BA (foliar and soaking) were evaluated. Theresults showed that increasing BA concentration increased all parametersmeasured relative to the controls, irrespective of the application method.The highest percentage of bud-break, the largest number of leaves, thelongest scion shoots and the most growth rating values were obtainedwith soaking in 400 mg BA/litre treatment, compared with the control orthe lower or higher BA concentrations tested or plants treated with thefoliar application method. No significant differences were obtainedamong BA concentrations tested or application methods used on scionshoot length. However, soak application method gave high values for allparameters measured compared with the soak application method.Treatment duration had no effect on the efficiency of BA on bud break.

Recommended resistant grape variety Traminette for quality winemaking

Тhe purpose of the variety study of the introduced white wine grape variety Traminette, originate at Cornell University, New York, USA in 1965, was to analyze the feasibility of its cultivation in the conditions of the northern zone of the industrial viticulture of the Russian Federation, for which the next objective were set: study in concrete soil and climatic conditions agrobiological and economically valuable characteristic and properties of the Traminette variety, such as yield, plasticity, resistance to biotic and abiotic environmental factors, as well as assess the quality of the resulting dry wine. To facilitate the identification of this variety, we made an ampelographic description according to the leading features. Тhe study was carried out in 2019-2021 according to the methods generally accepted in viticulture and winemaking in the grafted nursery of the Novocherkassk Experimental Field of the All-Russian Research Institute named after Ya.I. Potapenko for Viticulture and Winemaking – Branch of Federal State Budget Scientific Institution «FRARC» (Novocherkassk, Rostov Region). Тhe plantations are non-covered, non-irrigated, grafted, obtained by green grafting on the planted rootstock Oppenheim CO-4, planting scheme 3×1.5 m, medium-bole bush fan-shaped, medium pruning (4-6 buds left on the spoor). Тhe technology of cultivation of vineyards is standard and generally accepted. Тhe white wine variety Traminette of early-medium terms of grape ripeness, according to the variety study in the conditions of Novocherkassk, demonstrated winter hardiness sufficient for non-covering vineyards (the average long-term percentage of bud break is 79.8 %), high yield (10.2 t/ha), and increased resistance to fungal diseases (powdery mildew, downy mildew – 3.0, botrytis 1.5), excellent points for assessing dry wine material (8.7). All this makes the Traminette variety promising for use in industrial production in non-covering culture, with a decrease in the number of sprays compared to classical varieties, to obtain high quality wines.

PpyABF3 recruits the COMPASS-like complex to regulate bud dormancy maintenance via integrating ABA signaling and GA catabolism.

Bud dormancy is essential for perennial trees that survive the cold winters and to flower on time in the following spring. Histone modifications have been reported to be involved in the control of the dormancy cycle and DAM/SVPs are considered targets. However, how the histone modification marks are added to the specific gene loci during bud dormancy cycle is still unknown. Using yeast-two hybrid library screening and co-immunoprecipitation assays, we found that PpyABF3, a key protein regulating bud dormancy, recruits Complex of Proteins Associated with Set1-like complex via interacting with PpyWDR5a, which increases the H3K4me3 deposition at DAM4 locus. Chromatin immunoprecipitation-quantitative polymerase chain reaction showed that PpyGA2OX1 was downstream gene of PpyABF3 and it was also activated by H3K4me3 deposition. Silencing of GA2OX1 in pear calli and pear buds resulted in a similar phenotype with silencing of ABF3. Furthermore, overexpression of PpyWDR5a increased H3K4me3 levels at DAM4 and GA2OX1 loci and inhibited the growth of pear calli, whereas silencing of PpyWDR5a in pear buds resulted in a higher bud-break percentage. Our findings provide new insights into how H3K4me3 marks are added to dormancy-related genes in perennial woody plants and reveal a novel mechanism by which ABF3 integrates abscisic acid signaling and gibberellic acid catabolism during bud dormancy maintenance.

Studies to determine the optimum rates of nitrogen and potassium fertilization of Early Sweet grapevine under open field and plastic cover conditions

To determine the vines' optimum nitrogen and potassium fertilization rates of Early Sweet grape cultivar under open field and plastic cover conditions, the study was undertaken in the two periods of 2019 and 2020 with a preliminary season in 2018. Six treatments were applied in this experiment, three in an open field and three under a transparent plastic cover with different rates of (60, 45 and 30 units fed-1) for nitrogen and (100, 75 and 50 units fed-1) for potassium. Results showed that the vines receiving rates of N 45 units + K 75 units fed-1 under plastic cover recorded a higher percentage of bud break followed by N 60 units + K 100 units fed-1 treatment under plastic cover. In addition to an earlier sprout than those in the open field, they gave the highest values in term of yield and all physical and chemical parameters for reproductive growth, except for the vegetative growth where the best treatment was obtained from N 60 units + K 100 units fed-1 under plastic cover followed by N 60 units + K 100 units fed-1 in the open field. This result suggests that the plastic cover has a beneficial effect on decreasing the rates of fertilization due to the change in vine canopy microclimate through enhancing vegetative and reproductive growth and creating a balance between them.

Impact of Foliar-Applied Dormancy-Breaking Chemicals on Budburst and Metabolic Changes in Chemical Constituents of Leaves and Fruits of <i>Malus sylvestris</i> "Ein Shamer"

This study was carried out during the two successive seasons of 2016 and 2017 to investigate the impact of dormex, dormex plus mineral oil, dormex plus potassium nitrate, dormex plus calcium nitrate and dormex plus thiourea on bud break, growth, yield and some chemical constituents of Malus sylvestris "Ein Shamer". The trees were grown in loamy sand soil, and sprayed with six treatments (dormex (4%), (dormex (2%) plus mineral oil (2.5%),(dormex (2%) plus potassium nitrate (4%),(dormex (2%) plus calcium nitrate (4%) and (dormex (2%) plus thiourea (1%) and control. Generally, it was found that all studied growth parameters , date of flower bud break, percentage of bud break, fruit-setting ,fruit weight, fruit size, fruit number/tree, yield/tree (kg) and some chemical constituents of leaves (total chlorophyll ,total carbohydrates, total protein, nitrogen, phosphorous and potassium contents) and some chemical constituents of fruits (total soluble solids(T.S.S.), T.S.S/ acid ratio, vitamin C, water content %, total free amino acids, total carbohydrates, total sugars and reducing sugars) were increased with the application of the different treatments. The best results were obtained from the treatments of dormex at 4% followed by (dormex (2%) plus mineral oil (2.5%). On the contrary, the same treatments decreased total acidity and total phenols in fruits as compared to the control. It could be recommended to use dormex at 4% and (dormex (2%) plus mineral oil (2.5%) for improving bud break, growth, yield and chemical constituents of apple trees or fruits.

Budbreak patterns and phytohormone dynamics reveal different modes of action between hydrogen cyanamide- and defoliant-induced flower budbreak in blueberry under inadequate chilling conditions.

Under inadequate chilling conditions, hydrogen cyanamide (HC) is often used to promote budbreak and improve earliness of Southern highbush blueberry (Vaccinium corymbosum L. interspecific hybrids). However, HC is strictly regulated or even banned in some countries because of its high hazardous properties. Development of safer and effective alternatives to HC is critical to sustainable subtropical blueberry production. In this study, we examined the efficacy of HC and defoliants as bud dormancy-breaking agents for 'Emerald' blueberry. First, we compared water control, 1.0% HC (9.35 L ha-1), and three defoliants [potassium thiosulfate (KTS), urea, and zinc sulfate (ZS)] applied at 6.0% (28 kg ha-1). Model fitting analysis revealed that only HC and ZS advanced both defoliation and budbreak compared with the water control. HC-induced budbreak showed an exponential plateau function with a rapid phase occurring from 0 to 22 days after treatment (DAT), whereas ZS-induced budbreak showed a sigmoidal function with a rapid phase occurring from 15 to 44 DAT. The final budbreak percentage was similar in all treatments (71.7%-83.7%). Compared with the water control, HC and ZS increased yield by up to 171% and 41%, respectively, but the yield increase was statistically significant only for HC. Phytohormone profiling was performed for water-, HC- and ZS-treated flower buds. Both chemicals did not increase gibberellin 4 and indole-3-acetic acid production, but they caused a steady increase in jasmonic acid (JA) during budbreak. Compared with ZS, HC increased JA production to a greater extent and was the only chemical that reduced abscisic acid (ABA) concentrations during budbreak. A follow-up experiment tested ZS at six different rates (0-187 kg ha-1) but detected no significant dose-response on budbreak. These results collectively suggest that defoliants are not effective alternatives to HC, and that HC and ZS have different modes of action in budbreak induction. The high efficacy of HC as a dormancy-breaking agent could be due to its ability to reduce ABA concentrations in buds. Our results also suggest that JA accumulation is involved in budbreak induction in blueberry.

IMPACT OF FOLIAR-APPLIED DORMANCY-BREAKING AGENTS ON FLOWERING BEHAVIOR, YIELD, FRUIT QUALITY, AND SOME CHEMICAL CONSTITUENTS OF “EIN SHAMER” APPLE TREES

Objective: This investigation was carried out during the two successive seasons of 2016 and 2017 to investigate the effect of Dormex, mineral oil, potassium nitrate, calcium nitrate, and thiourea on bud break, growth, yield, and some chemical constituents of “Ein Shamer” apple (Malus sylvestris, Mill) variety.
 Methods: The trees were grown in loamy sand soil, and sprayed with six treatments (Dormex (4%), mineral oil (5%), potassium nitrate (8%), calcium nitrate (8%), and thiourea (2%) and control.
 Results: In general, it was found that all studied growth parameters, date of flower bud break, percentage of bud break, fruit-setting, fruit weight, fruit size, fruit number/tree, yield/tree (kg), and some chemical constituents of leaves (total chlorophyll, total carbohydrates, total protein, nitrogen, phosphorous, and potassium contents) and some chemical constituents of fruits total soluble solids (T.S.S.), T.S.S./acid ratio, Vitamin C, water content %, total free amino acids, total carbohydrates, total sugars, and reducing sugars) were increased with the application of the different treatments.
 Conclusion: The best results were obtained from the treatment of Dormex at 4% and mineral oil (5%). On the contrary, the same treatment decreased total acidity and total phenols in fruits as compared to the control. It could be recommended to use Dormex at 4% and mineral oil (5%) for improving bud break, growth, yield, and chemical constituents of apple trees or fruits.

Secondary and tertiary budbreak release is enhanced by extended dormancy chilling in 'Shiraz' grapevines

Limited information exists regarding the dormancy of secondary and tertiary buds within the compound bud of grapevines. We were interested to evaluate how extended chilling duration would affect the budbreak percentage of all three bud orders within the compound bud. Dormant potted 'Shiraz' grapevines, with thirty retained buds per vine, were placed in a cool room at 4 °C over a 20-month period to extend dormancy. Vines were then systematically removed over five dates and placed in a controlled growth environment to assess budbreak percentages and cane tissue concentrations of abscisic acid and cytokinins. Budbreak was hastened by at least 13 d with vines receiving any extra chilling compared to no initial chilling. Furthermore, the firstly observed correlative inhibition of basal buds was apparently removed with chilling. Removal of correlative inhibition within the compound bud with increased chilling duration was also observed with the increases of secondary (doubles) and tertiary (triples) buds breaking simultaneously with the primary bud at each node. This resulted in 91 % of the nodes having two developing shoots and 56 % of the nodes presenting three developing shoots by the end of the experiment. Furthermore, a sigmoidal relationship between percent secondary buds and chilling duration was observed. Possible phytohormone connections were observed with the decline of ABA as secondary and tertiary buds broke at 414 d of chilling and depletion of the CKs, which coincided with the greatest rate of primary bud break after 242 d of chilling. Other possible involvement of ABA and Cis-type cytokinin interactions with secondary and tertiary bud dormancy is discussed. The results suggest future investigations into secondary and tertiary bud release within the grapevine using similar techniques may help to better understand the biochemical mechanisms associated with dormancy.

Foliar Application of Defoliants before Winter Chill Accumulation Advances Budbreak and Improves Fruit Earliness of Blackberry under Subtropical Climatic Conditions

In subtropical blackberry (Rubus L. subgenus Rubus Watson) production, inadequate winter chill causes poor and erratic budbreak, whereas high temperatures and heavy rainfall deteriorate late-season fruit quality. We examined the effects of four defoliants [zinc sulfate (ZS), potassium thiosulfate (KTS), urea, and lime sulfur (LS)] on defoliation, budbreak, yield, and fruit quality of ‘Natchez’ blackberry grown under inadequate chilling conditions in two consecutive growing seasons. Plants were treated with defoliants at 187 kg·ha−1 via spray application (1870 L·ha−1) at the beginning of chill accumulation (late December). A nonionic surfactant (Agri-Dex) was added at 0.5% (v/v) to all treatments including the water control. Cumulative chilling hours (<7.2 °C) at the experiment site were 209 and 134 in the first and second growing seasons, respectively. Defoliation was only 40.2% to 55.5% in the control, but it was induced moderately by LS (69.7% to 84.7%) and severely by the other defoliants (81.7% to 94.7%). Budbreak was induced most rapidly by urea application, followed by LS, KTS, and ZS, advancing by 17 to 66 days compared with the control. Consequently, urea, KTS, LS, and ZS increased early season yield by 2.79, 2.55, 0.87, and 0.31 t·ha−1, respectively, compared with the control (0.12 t·ha−1). By contrast, the final percentage of budbreak and total-season yield did not show significant treatment effects. KTS caused cane dieback and increased bud mortality, resulting in the lowest total-season yield among the treatments. Importantly, defoliants had no negative impact on berry size and soluble solids concentration. These results suggest that urea, LS, and ZS are effective bud dormancy-breaking agents for blackberry and that they could be an important adaptation tool for subtropical blackberry production. Among the three defoliants, urea appears to be the ideal chemical option because of its consistent efficacy, favorable safety profile, and low application cost.

APPLICATION OF BENZYLADENINE (BA) IN THE FORM OF LANOLIN PASTE ON FLOWER-STALK BUDS SUCCESSFULLY INDUCED RE-BLOOMING OF HYBRID Phalaenopsis

Hybrid moth orchid (genus Phalaenopsis) is one of the most popular ornamentals in Indonesia. It has beautiful and long-lasting flowers, but cultivating this orchid is still become a challenging issues due to the need of specific condition to grow and long time period to re-blooming. Plant growth regulators (PGR) (i.e. Benzyladenine (BA)) has been widely documented as a flower-inducing substance in several orchids. However, the optimal concentration and its mechanism in inducing flower-stalk bud and re-blooming is still unclear. This research aimed to study the effects of BA application in the form of lanolin paste on hybrid Phalaenopsis flower-stalk buds. We conducted this study using completely randomized design with four replications at the greenhouse laboratory Faculty of Agriculture University of Lampung on August to December 2018. We divided the orchid into 5 group of BA concentration (0, 1000, 1500, 3000, or 6000 ppm). The sheath of the fourth or fifth buds of the flowers were carefully opened, then it smeared with BA. The percentage of bud break into flower spike or keiki, length of shoots or spike and number of open flowers were recorded until 10 weeks of observation. The results showed that, neither of the buds under the control treatment (without BA), 1000 ppm nor 1500 ppm BA broke and grew into keiki or spike. On the other hand, application of BA at 3000 ppm or 6000 ppm successfully induced 100% flower spikes on the buds treated. No keiki was formed in all buds treated. In addition, treatment of the buds with 6000 ppm BA produced longer flower spikes as well as more open flowers. We conclude that the application of BA (minimal 3000 ppm) successfully induced flower spike of hybrid Phalaenopsis.

Changes in the Endogenous Content and Gene Expression of Salicylic Acid Correlate with Grapevine Bud Dormancy Release

The accumulation of cold temperature is an important factor for the release of bud dormancy in grapevine. The stress generated by cold is related to changes in defense hormones such as salicylic acid (SA). To understand the participation of this hormone during grapevine bud dormancy release, in this study, we evaluated the effects of cold accumulation on the endogenous SA content and expression patterns of the synthesis and signaling genes of SA as well as budbreak rates. Buds were subjected to an accumulation of 900 or 600 chilling units (CUs). The budbreak percentage was determined when cold-treated buds were transferred to warm temperatures (25 °C). The percentage of budbreak was closely correlated with the amount of cumulative CUs; the percentage increased gradually with the amount of chilling applied before forcing. The increase in the expression level of the SA biosynthesis gene (ICS2) and the endogenous SA content were quantified in cold-treated buds, and the expression was correlated with the percentage of budbreak. These findings may indicate that in dormant grapevine buds, cold accumulation stimulates the synthesis of SA. In cold-treated buds, the cellular levels of SA led to the expression of the NPR1 and PR1 genes, which was mediated by the transcription factor WRKY70. In contrast, expression of NPR1 and PR1 in control buds, which maintained a basal level of SA, and expression of ICS2 and WRKY70 were not detected, suggesting that the constitutive expression of NPR1-SA is independent. Taken together, the results of this study suggest a possible involvement of the SA signaling pathway in grapevine bud dormancy release.

Autochthonous Georgian and Dagestan grapevine varieties on the collection in the Rostov region

The purpose of the research was to study 8 Georgian and 3 Dagestan technical autochthonous grapevine varieties and identify the most productive and promising ones for high-quality winemaking in the Rostov region. The research was conducted in 2016-2019 at Don ampelographic collection named after Ya.I. Potapenko (Novocherkassk, Russia) according to generally accepted methods and state Standards in viticulture. Don autochthonous varieties Sibirkovyij and Krasnostop zolotovskij were used as controls. The soil - ordinary Chernozem carbonate. All the studied varieties had a high percentage of bud break (from 69.3% in Hotsa tsibil to 81.2% in Mahbor tsibil). The fruiting coefficient of 1.0 or more was observed in 6 varieties. The average weight of a bunch varied from 74 g (Mudzhuretuli) to 459 g (Adreuli shavi). The estimated yield was very high for the varieties – Adreuli shavi and Nakutvneuli, high – Goruli mtsvane, Hotsa tsibil, medium – Latsu kere, Grdzelmtevana, Grubela, Amlakhu, Sibirkovyij, Vernakhi and Krasnostop zolotovskij. Grapevine varieties – Goruli mtsvane, Grdzelmtevana, Grubela, Latsu kere, Hotsa tsibil, Nakutvneuli were selected as prospective due to agronomic traits and high quality of wine. These varieties are also recommended to be used in breeding for creating varieties with high technological properties for high-quality winemaking.

Effects of gibberellins A4 on budbreak, antioxidant enzymes’ activity and proline content of flower buds in sweet cherry (Prunus avium)

Chilling accumulation is required for deciduous trees to maintain its normal growth and development. However, warm winters appeared more and more frequently, which hindered severely the normal growth and yield of fruit trees. To avoid these problems, artificial dormancy breaking agents are widely used. In our study, the effect of mineral oil, hydrogen cyanamide and gibberellins A4 (GA4) on budbreak were evaluated in sweet cherry (Prunus avium), which indicated that GA4 treatment hastened the date of flower budbreak and increased the percentage of budbreak compared with the other treatments. To better understand the mechanism of GA4-induced budbreak, the contents of antioxidant enzymes’ activity and proline in sweet cherry flower buds treated with GA4 and water were evaluated. There was a sharp decrease of catalase (CAT) activity after 5 days of GA4 treatment and then an increase of CAT activity after 10 days of GA4 treatment. However, there was a sharp increase of superoxide dismutase (SOD), peroxidase (POD) and ascorbate peroxidase (APX) after 5 days of GA4 treatment and then a decrease of these enzyme activities after 10 days of GA4 treatment. There was a transient increase in hydrogen peroxide (H2O2) content and proline content after 5 days of GA4 treatment and a decrease after 10 days of GA4 treatment. However, there were only small fluctuations after water treatment, which indicated that temporary oxidative stress may contribute to the dormancy release of flower buds in the sweet cherry treated with GA4 through the regulation of H2O2 content coincided with the changes of antioxidant defense system.

Effects of bub nodal position along the cane on bud fertility, yield component and bunch structure in ‘Carménère’ grapevines

Carmenere is an important grapevine (Vitis vinifera L.) variety from the Chilean wine industry, which has a low fertility in their basal buds, affecting negatively yield. Due to this, the aim of this work was to characterize and evaluate technological maturity, percentage of bud break, practical bud fertility, yield components, bunch structure and yield index by practical fertility reached in each nodal position in buds along Carmenere canes. Bud break reached an average of 79.9% along the cane, with extreme values from 57.3% to 98.7%. Bud fertility reached an average of 1.3 bunch per bud, with extreme values from 0.9 to 1.7. According to this, ‘Carmenere’ showed a low fertility in basal buds. Weight of bunch varied from 108.0 to 214.7 g. Number and weight of berries was higher in the buds from distal nodal positions. Bunch structure parameters, such as stalk length, number and length of primary wings, and yield index by practical fertility was also higher in the bud from distal nodal positions. Moreover, large size berries represent 50% of berries and 80% of weight of berries. Due to this, ‘Carmenere’ productivity is limited by small size berries. These findings are important to determine the viticultural managements that should be performed in ‘Carmenere’ vineyards.

Yield potential definition of the chilling requirement reveals likely underestimation of the risk of climate change on winter chill accumulation.

Evaluation of chilling requirements of cultivars of temperate fruit trees provides key information to assess regional suitability, according to winter chill, for both industry expansion and ongoing profitability as climate change progresses. Traditional methods for calculating chilling requirements use climate-controlled chambers and define chilling requirements (CR) using a fixed bud burst percentage, usually close to 50% (CR-50%). However, this CR-50% definition may estimate chilling requirements that lead to flowering percentages that are lower than required for orchards to be commercially viable. We used sweet cherry to analyse the traditional method for calculating chilling requirements (CR-50%) and compared the results with a more restrictive method, where the chilling requirement was defined by a 90% bud break level (CRm-90%). For sweet cherry, this higher requirement of flowering success (90% as opposed to 50%) better represents grower production needs as a greater number of flowers leads to greater potential yield. To investigate the future risk of insufficient chill based on alternate calculations of the chilling requirement, climate projections of winter chill suitability across Europe were calculated using CR-50% and CRm-90%. Regional suitability across the landscape was highly dependent on the method used to define chilling requirements, and differences were found for both cold and mild winter areas. Our results suggest that bud break percentage levels used in the assessment of chilling requirements for sweet cherry influence production risks of current and future production areas. The use of traditional methods to determine chilling requirements can result in an underestimation of productivity chilling requirements for tree crops like sweet cherry which rely on a high conversion of flowers to mature fruit to obtain profitable yields. This underestimation may have negative consequences for the fruit industry as climate change advances with climate risk underestimated.

Time-to-event analysis to evaluate dormancy status of single-bud cuttings: an example for grapevines

BackgroundThe reduced growth of plants during the winter causes a lack in the perceptibility of the phenological events making challenging the study of dormancy. For deciduous crops, dormancy is generally determined by evaluating budbreak of single-node cuttings that are exposed to conditions suitable for growth. However, the absence of a statistical basis for analyzing and interpreting the budbreak behavior evaluated as the percent budbreak, the average time to budbreak and the time to reach 50% budbreak, has caused inconsistent and contradictory criteria to identify the dormancy status of different deciduous crops.ResultsIn this study, a method was developed to analyze the duration between sampling and budbreak of single-node cuttings and to estimate the dormancy status for grapevines (Vitis vinifera L.) based on the time-to-event distribution of the observations. This method estimates the probability curve of budbreak for each sample and classifies each curve into paradormancy, endodormancy, and ecodormancy according to the significance when compared to a sample curve estimated from cuttings collected during paradormancy and referred to as “reference.”ConclusionThe approach described in this study provided a comparison of the budbreak distribution of cuttings collected during distinct phases with a confidence of 95%. It also allowed the estimation of the date of occurrence of the dormancy stages for two grapevine cultivars ‘Cabernet Sauvignon’ and ‘Chardonnay,’ based on the variability within the sampling season rather than on fixed arbitrary criteria. This approach can also be used to analyze budbreak data of single-node cuttings from other common deciduous crops.

Metabolic Changes in Polyamines, Phenylethylamine, And Arginine During Bud Break in Apple Flower Buds Under Foliar-Applied Dormancy-Breaking Agents

The Environmental and climatic conditions affect the flower bud growth, flowering and yield performance of fruit species. Temperature appears to be important factors for temperate fruit trees in mild climates. The relationships between breaking bud dormancy and climatic influences on flowering, growth and metabolic changes in contents of biogenic amines (spermine, spermidine, putrescine, cadaverine and phenylethylamine), arginine and anthocyanin before and after bud break were evaluated for "Ain Shemer" apple (Malus sylvestris, Mill) trees under exogenously applied hydrogen cyanamide (dormex), calcium nitrate Ca(NO3)2 and thiourea. The studies have shown that breaking bud dormancy (as early date of bud break and percentage of bud break) by the above dormancy breaking agents were correlated with the high content of biogenic amines and arginine in buds. Seasonal variations in biogenic amines, arginine and anthocyanin level were present in buds during the research period (dormancy and dormancy release period). Levels of spermine, spermidine, putrescine, cadaverine, phenylethylamine, arginine and anthocyanin have simultaneously risen with bud burst and new growth. The most abundant polyamines in buds were cadaverine followed by spermine. The best results were obtained with Dormex after exposure the trees to about 274 natural chilling hours ? +7.2oC; therefore, we recommend using this compound to achieve bud break as early as possible in "Ain Shemer" apple variety by regulating the contents of biogenic amines and arginine in buds and subsequently the high percentages of bud break and maximum yield.

Starch, growth, and development in cuttings of rootstock 'Paulsen 1103' from plants infested with ground pearl

ABSTRACT: The ground pearl, Eurhizococcus brasiliensis , is considered an important pest of vineyards in southern Brazil, with affected plants exhibiting leaf chlorosis, reduction in vigor, fading, and death. This study evaluated the quality of hardwood cuttings produced from plants infected (I) and not infected (NI) by ground pearl. 'Paulsen 1103' ( Vitis berlandieri × Vitis rupestris ) plants were grown for 29 months in brick-built raised beds either infested or not infested by ground pearl; then, 12 one-year-old branches with a maximum of 12 buds each were cut from each plant, subdivided into three portions (4 buds cutting-1), and subjected to destructive and nondestructive testing. DDestructive testing comprised determining fresh and dry weight, length, internode diameters, and percentage of starch. Nondestructive testing comprised assessing the potential for bud sprouting and shoot development. Each mother plant in the I and NI beds was considered a replicate, with a total of 360 cuttings per treatment. It was observed that cuttings from infected plants had significantly lower (P<0.05) internode diameter, length, and fresh and dry weight than those of the uninfected plants. The percentage of starch content of the cuttings did not differ significantly. All cuttings showed the same percentage (100%) of bud breaking and no changes in growth and development of seedlings regardless of source. Given these results, it was concluded that vines of 'Paulsen 1103' infested with ground pearl produce smaller cuttings than those of uninfected plants but with no reduction in bud break percentage or seedling development