Bud Break Stage Research Articles

Whole-genome characterization of CKX genes in Prunus persica and their role in bud dormancy and regrowth

Dud dormancy is a complex physiological process of perennial woody plants living in temperate regions, and can be affected by various phytohormones. Cytokinin oxidase/dehydrogenases (CKXs) are a group of enzymes essential for maintaining cytokinin homeostasis, but a comprehensive analysis in peach is lacking. Here, a total of 51 CKX members from different species, including six from peach, eleven from apple, nine from poplar, seven from Arabidopsis, eight from strawberry and ten from rice, which were identified using The Simple HMM Search tool of TBtools and a BLASTP program, were classified into four groups using phylogenetic analysis. Conserved motif and gene structure analysis of these 51 CKX members showed that ten conserved motifs were identified, and each CKX gene contained at least two introns. Cis-element analysis of PpCKXs showed that all of the PpCKX genes have light-responsive elements and at least one hormone-responsive element. The obviously changed relative expression <pg=>levels of six PpCKX genes in peach buds from endodormancy to bud-break were observed by qRT-PCR. Among them, the expression trend of PpCKX6 was almost opposite that of PpEBB1, a positive bud-break regulator in woody plants, around the bud-break stage. Y1H, EMSA, and dual-luciferase assays indicated that PpEBB1 negatively regulated PpCKX6 through direct binding to a GCC box-like element located in the promoter region of PpCKX6. In addition, a transient assay showed that overexpression of PpCKX6 delayed bud-break of peach. These results indicate that the PpCKX genes play an important role in the dormancy-regrowth process and PpCKX6 may act downstream of PpEBB1 directly to regulate bud-break process, which further improves the hormone-regulatory network of dormancy-regrowth of woody plants, and provides new insights for molecular breeding and genetic engineering of peach.

Altitudinal Patterns of Foliar Nutrients in Dominant Tree Species: Are Central Himalayan Forests Nutrient Stressed?

In forest ecosystems nutrient availability is one of the most important drivers of tree growth and ecosystem function. We studied changes in soil and foliar nutrients (N, P &amp; K) and leaf N and P stoichiometry in eight dominant canopy and sub-canopy forest tree species of Central Himalayan forests occurring between 300 and 2200 m asl. Nutrient (N, P &amp; K) concentration in leaves at bud break, mature and senescent stage varied significantly across the tree species. The nutrient resorption efficiency (NRE) varied significantly across the species and found ranging for N from 48.7 - 76.8%. Both the nitrogen resorption efficiency (NRE) and phosphorus resorption efficiency (PRE) increased linearly with altitude (R2= 0.647 for NRE significant at p&lt; 0.05; and R2 for PRE= 0.525; NS) pointing out that trees growing in temperate climate conserve nutrients more efficiently to withstand the slow mineralization due to cold climate. With the increasing altitude leaf life-span increases significantly (R2= 0.0025; p&lt; 0.0074). ANOVA indicates that the foliar N and P and altitude were unrelated. The low N: P ratio, a measure of nutrient status of forest ecosystems at senescent leaf stage, found ranging from 9.97 in Q. floribunda to 18.8 in P. roxburghii points out that forests of the study region are nutrient stressed, partly due to low P mineralization in temperate climate, leaching of nutrients due to heavy monsoon rain, and poorly developed underlying geology. Thus, the Central Himalayan forests are characterized by high NRE and low growth rate with increasing altitude. Winter season warming might help improve the nutrient availability in the forest floor and nutrient uptake to enhance nutrient cycling and biomass productivity in these forests.

Genome-wide identification and comparative analysis of DNA methyltransferase and demethylase gene families in two ploidy Cyclocarya paliurus and their potential function in heterodichogamy

BackgroundDNA methylation is one of the most abundant epigenetic modifications, which plays important roles in flower development, sex differentiation, and regulation of flowering time. Its pattern is affected by cytosine-5 DNA methyltransferase (C5-MTase) and DNA demethylase (dMTase). At present, there are no reports on C5-MTase and dMTase genes in heterodichogamous Cyclocarya paliurus.ResultsIn this study, 6 CpC5-MTase and 3 CpdMTase genes were identified in diploid (2n = 2 × = 32) C. paliurus, while 20 CpC5-MTase and 13 CpdMTase genes were identified in autotetraploid (2n = 4 × = 64). 80% of identified genes maintained relatively fixed positions on chromosomes during polyploidization. In addition, we found that some DRM subfamily members didn’t contain the UBA domain. The transcript abundance of CpC5-MTase and CpdMTase in male and female flowers of two morphs (protandry and protogyny) from diploidy was analyzed. Results showed that all genes were significantly up-regulated at the stage of floral bud break (S2), but significantly down-regulated at the stage of flower maturation (S4). At S2, some CpC5-MTase genes showed higher expression levels in PG-M than in PG-F, whereas some CpdMTase genes showed higher expression levels in PA-M than in PA-F. In addition, these genes were significantly associated with gibberellin synthesis-related genes (e.g. DELLA and GID1), suggesting that DNA methylation may play a role in the asynchronous floral development process through gibberellin signal.ConclusionsThese results broaden our understanding of the CpC5-MTase and CpdMTase genes in diploid and autotetraploid C. paliurus, and provide a novel insight into regulatory mechanisms of DNA methylation in heterodichogamy.

Integrated genome-wide chromatin accessibility and expression profile identify key transcription factors involved in bud endodormancy break in tea plants

It is essential for tea plants (Camellia sinensis) to undergo bud endodormancy in order to survive winter and grow again the following spring. Molecular pathways underlying the release and break of endodormancy, however, remain unclear. Accessible chromatin regions play a crucial role in precise gene expression regulation. Here, we profiled the chromatin accessibility and transcriptional features of transcription factors (TFs) using ATAC- and RNA-seq technologies. We revealed dynamic changes during bud dormancy break in tea plants and detected open chromatin regions and TF binding sites. Numerous transcripts associated with open chromatin regions were found to exhibit dormant-preferential expression among TF-target genes. We focused on several crucial TF motifs, including MADS-box, AP2EREBP, bZIP, MYB, bHLH, E2FDP, REMB3, TCP, and G2-like factors, that were enriched in open chromatin regions at different budbreak stages, and predicted networks of TF-target genes. Then, we used qRT-PCR to investigate the expression patterns of budbreak-related genes.We found a set of differentially regulated peaks of MADS-box TFs and related genes enriched in plant hormone signal transduction pathway, photosynthesis, secondary metabolism, plant-pathogen interaction functions. Correlation analysis with the phytohormones abscisic acid and indole-3-acetic acid also provided details of the regulation network. Moreover, we identified the core TFs (SVP, CO, AP1, SOC, ABI, CBF, FRUITFULL, and ULTRAPETALA) of several pathways related to budbreak, providing the guideposts for future study.

Assessment of Physio-Chemical, Nutritional and Enzymatic Activities in the Bud in Relation to Flowering Behaviours of Different Alternate Bearing Mango (Mangifera indica L.) Cultivars

ABSTRACT Most of the commercial mango cultivars have the tendency of alternate bearing, which significantly reduces the productivity and profitability of the crop. But literatures on the exact physiological mechanism behind flowering in mango during on and off year are very scanty. Hence, an attempt has been made to understand the physio-chemical and nutritional basis for on- and off-season bearing in different commercial mango cultivars. Specific leaf weight and net assimilation rate were increased marginally at panicle emergence stage as compared to bud break stage. Carbohydrate and soluble protein contents in the bud at bud break stage were estimated significantly higher in on-season trees (195.25 µg g−1 and 5.73 mg 100 g−1, respectively). Activities of oxidative enzymes (polyphenol oxidase, peroxidase, catalase) in the bud were recorded significantly higher in off-season trees. Nitrogen, phosphorus and potassium contents in the bud at bud break stage were estimated significantly higher in off-season trees (1.52, 0.22 and 0.53%, respectively), although secondary and micronutrient contents were estimated higher in on-season one. Finally, the generative buds per branch were estimated significantly higher in on-season trees (90.66%) as compared to off-season one (18.68%). Hence, it can be concluded that increased physio-chemical attributes in the bud at bud break stage has direct relation with panicle emergence in mango. However, increased macronutrients and higher activities of oxidative enzymes leads to off-season bearing, although increased secondary and micronutrient contents in the bud at bud break stage are helpful for improved flowering in mango.

Foliar application of ethephon induces bud dormancy and affects gene expression of dormancy- and flowering-related genes in ‘Mauritius’ litchi (Litchi chinensis Sonn.)

A previous study showed that foliar application of ethephon to litchi trees with mature shoots and dormant terminal buds during autumn successfully inhibited new vegetative shoot growth prior to floral induction thereby promoting carbohydrate accumulation and flowering. However, the functional mechanisms of ethylene, the breakdown product of ethephon, in the leaves and terminal buds of litchi and its involvement in the flowering process is largely unknown. Therefore, this study aimed to investigate the phenological, physiological and molecular changes underlying ethephon application and its associations with bud dormancy and flowering in litchi. Ethephon was applied as a single full canopy spray at a concentration of 1000 mg⋅L−1 to ‘Mauritius’ litchi trees with mature vegetative shoots and dormant terminal buds during late autumn of 2018 (mid-April; Southern Hemisphere). Untreated trees served as a control. Phenological characteristics, such as bud dormancy and panicle development, leaf chlorophyll (as an indicator of shoot maturity), ethylene evolution, gene expression levels of flowering- (LcFT2, LcFLC and LcAP1), dormancy- (LcSVP1 and LcSVP2) and ethylene pathway-related (LcEIN3) genes and non-structural carbohydrates were determined in terminal buds, leaves and/or shoots. Ethephon application induced bud dormancy, significantly delayed panicle emergence and promoted pure floral panicle development under more favorable inductive conditions. Ethylene evolution increased sharply 2 h after application in both leaves and terminal buds, but decreased rapidly thereafter in the leaves, while remaining high in terminal buds for seven days before gradually declining. Ethephon application significantly increased relative expression of LcEIN3 and LcFLC in terminal buds one day after application, while LcFT2 expression in leaves and LcAP1 expression in terminal buds were significantly increased at the bud break stage. Significant treatments differences were also observed for various carbohydrate metabolites in leaves and shoots at the bud break or floral initiation stage. Our study provided evidence that ethephon application plays an important role in the physiological and molecular regulation of bud dormancy of litchi. By influencing the time of bud break, ethephon application can be a useful tool to manage panicle emergence under less inductive conditions.

Effect of plant growth regulator (PGR) and cultural practices on supression of post monsoon vegetative flush in relation to physiological and yield parameters of alphonso mango (Mangifera indica L.)

This experimental work was performed on Alphonso mango treeat Centre of Excellence for Mango, Department of Horticulture, Dr. Balasaheb Sawant Konkan KrishiVidyapeeth, Dapoli, during mango growing season summer-winter 2016 -2017 and 2017-2018. It is observed that the post- monsoon vegetative flush in mango trees affects reproductive phase that ultimately cause huge economic loss and so the study aimed at the effect of plant growth regulator (PGR) and cultural practices on supression of post monsoon vegetative flush in relation to physiological and yield parameters. The experiment laid out in ten treatments viz,. T1_ control,T2_ CCC-1500 ppm,T3_CCC-2500 ppm,T4_foliar spray of diammonium phosphate 3%,T5_PBZ-500 ppm,T6_PBZ-1000 ppm,T7_ PBZ- 2000 ppm,T8_ Soil opening upto the depth of 4-5 inch at tree basin region once in last week of September,T9_ Soil opening upto the depth of 4-5 inch at tree basin region once in last week of October and T10_Soil opening upto the depth of 4-5 inch at tree region twice in last week of September and last week of October. Among physiological parameters considered, the rate of photosynthesis was maintained at significantly highest rate (7.44 μmol CO2 m-2s-1) by treatment T10. The rate of respiration was found to be increased from before bud break stage to bud break stage and then declines towards flower initiation stage. In case of rate of transpiration, treatment T10 maintained significantly highest rate of respiration from before bud break stage to flower initiation stage and recorded highest rate of respiration at bud break stage (-6.03 μmol CO2 m-2s-1). In case of yield, treatment T10 recorded significantly minimum days required for harvesting (102.16 days) from flowering among all treatments. Significantly maximum days required for harvesting (129.83 days) was recorded by T1.The treatment T10 recorded significantly maximum number of fruits per plant (188.50) followed by treatment T3 (184.16), significantly minimum fruits per tree (89.50) was recorded by T1.The fruits per tree (kg) was found to be significantly higher (48.96 kg) in T10.

Antioxidant enzymes activity in ‘Castel Gala’ apple trees after the budbreak inducers application

Since antioxidant enzymes activity affects the end of dormancy stage, it is important to understand the responses given by antioxidant enzymes and their roles in budbreak induction in temperate fruit trees. This research aimed at evaluating the antioxidant enzymes activity at the end of budbreak stage after the inducers application to ‘Castel Gala’ apple trees and their performance in budbreak and blooming. Seven treatments were carried out: Erger® 3% + calcium nitrate 5%; Erger® 5% + calcium nitrate 5%; Erger® 7% + calcium nitrate 5%; garlic extract (GE) 5% + mineral oil (MO) 2%; GE 10% + MO 2%; GE 15% + MO 2%; and the control. Buds were collected one, four and seven days after the application (DAA) of budbreak inducers, and activity of the following enzymes was determined by: superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX). Besides that, hydrogen peroxide was quantified. Percentages of budbreak and blooming were evaluated at 32th, 40 th, 45 th and 52 th DAA. The results showed that SOD activity had increased as the dormancy stage reached its end. CAT activity was influenced by the application of budbreak inducers. It decreased significantly throughout the experiment in the most efficient treatment. Percentages of budbreak (61.85%) and blooming (25.44%) showed the highest efficiency in the treatment with Erger® 7% + calcium nitrate 5%, which was the inducer with the highest potential in ‘Castel Gala’ apple trees

Genome-Wide Changes of Regulatory Non-Coding RNAs Reveal Pollen Development Initiated at Ecodormancy in Peach.

Bud dormancy is under the regulation of complex mechanisms including genetic and epigenetic factors. To study the function of regulatory non-coding RNAs in winter dormancy release, we analyzed the small RNA and long non-coding RNA (lncRNA) expression from peach (Prunus persica) floral buds in endodormancy, ecodormancy and bud break stages. Small RNAs underwent a major shift in expression primarily between dormancy and flowering with specific pairs of microRNAs and their mRNA target genes undergoing coordinated differential expression. From endodormancy to ecodormancy, ppe-miR6285 was significantly upregulated while its target gene, an ASPARAGINE-RICH PROTEIN involved in the regulation of abscisic acid signaling, was downregulated. At ecodormancy, ppe-miR2275, a homolog of meiosis-specific miR2275 across angiosperms, was significantly upregulated, supporting microsporogenesis in anthers at a late stage of dormancy. The expression of 785 lncRNAs, unlike the overall expression pattern in the small RNAs, demonstrated distinctive expression signatures across all dormancy and flowering stages. We predicted that a subset of lncRNAs were targets of microRNAs and found 18 lncRNA/microRNA target pairs with both differentially expressed across time points. The genome-wide differential expression and network analysis of non-coding RNAs and mRNAs from the same tissues provide new candidate loci for dormancy regulation and suggest complex noncoding RNA interactions control transcriptional regulation across these key developmental time points.

Integrating chlorophyll fluorescence parameters into a crop model improves growth prediction under severe drought

Predicting biomass production is important for assessing yield losses caused by drought. Photosynthesis-driven crop growth models, such as SUCROS97, tend to overestimate crop production under severe drought, as they ignore slow post-drought recovery kinetics of leaf photosynthesis. In this study, Lilium plants (L. auratum × speciosum ‘Sorbonne’) were subjected to mild, intermediate and severe drought with different durations (3, 5, 7 and 9 days) at two developmental stages (leaf unfolding and flower bud break stage). Leaf photosynthesis and chlorophyll fluorescence (CF) were measured during and after drought. We found that at both developmental stages, drought significantly reduced light-saturated gross photosynthesis rate (Pg,max), which progressively recovered after re-watering. Under mild drought, Pg,max recovered fully to non-stress levels by re-watering, whereas under intermediate and severe drought, Pg,max did not recover fully. Drought occurring during leaf unfolding had a larger impact on biomass production than drought during bud break. Further, we identified a sigmoidal relationship (r2 = 0.81) between Pg,max and photosystem II operating efficiency (Φ2) during drought, and highly linear relationships (r2 = 0.88) between Pg,max and the quantum yield of non-regulated energy dissipation (ΦNO) during post-drought recovery. We integrated the aforementioned relationships into SUCROS97, and the extended SUCROS-CF model explicitly accounted for slow and incomplete Pg,max recovery in the post-drought phase. Compared to SUCROS97, SUCROS-CF improved biomass prediction by 7%, due to a 19% improvement in Pg,max predictions under severe drought. We conclude that to accurately predict productivity during and after severe drought, leaf photosynthetic capacity kinetics need to be considered. Furthermore, CF measurements can be applied to predict leaf photosynthetic capacity during and after drought, enabling rapid drought phenotyping in breeding programs and yield loss assessment in the field.

Morphological Characterization of Flower Buds Development and Related Gene Expression Profiling at Bud Break Stage in Heterodichogamous Cyclocarya paliurus (Batal.) lljinskaja.

Cyclocarya paliurus (Batal.) Iljinskaja, a unique species growing in southern China, is a multi-function tree species with medicinal, healthcare, material, and ornamental values. So far, sexual reproduction is the main method for extensive cultivation of C. paliurus plantations, but this is limited by low seed plumpness resulted from the character of heterodichogamy. Phenological observations have revealed the asynchronism of flower development in this species. However, its molecular mechanism remains largely unknown. To reveal molecular mechanism of heterodichogamy in C. paliurus, transcriptome of female (F) and male (M) buds from two mating types (protandry, PA; protogyny, PG) at bud break stage were sequenced using Illumina Hiseq 4000 platform. The expression patterns of both 32 genes related to flowering and 58 differentially expressed transcription factors (DETFs) selected from 6 families were divided four groups (PG-F, PG-M, PA-F, and PA-M) into two categories: first flowers (PG-F and PA-M) and later flowers (PA-F and PG-M). The results indicated that genes related to plant hormones (IAA, ABA, and GA) synthesis and response, glucose metabolism, and transcription factors (especially in MIKC family) played significant roles in regulating asynchronism of male and female flowers in the same mating type. The expression of DETFs showed two patterns. One contained DETFs up-regulated in first flowers in comparison to later flowers, and the other was the reverse. Nine genes related to flowering were selected for qRT-PCR to confirm the accuracy of RNA-seq, and generally, the RPKM values of these genes were consistent with the result of qRT-PCR. The results of this work could improve our understanding in asynchronism of floral development within one mating type in C. paliurus at transcriptional level, as well as lay a foundation for further study in heterodichogamous plants.

Effects of gibberellic acid applications on induction of partenocarpy in black myrtle fruits

Myrtle (Myrtus communis L.) is an evergreen aromatic and medicinal bush native to the Mediterranean Basin. It has long been considered an important fruit since ancient times especially because of its use for medical purposes. Myrtle oil is also conventionally produced from the leaves by traditional distillation methods. Myrtle fruits are consumed fresh by people of the Mediterranean Basin. The common complaints by the consumers is the small fruit size as well as the high number of seed in fruits. The main aim of this study was to test the impact of the application of gibberellic acid (GA(3)) on seed counts and seedlessness (parthenocarpic fruit) in black myrtles by utilizing 50, 100 and 200 ppm GA(3) applications. GA(3) was applied as spray to the leaves a week before bud break and blooming period. None of the three GA(3) applications at the bud break stage had any significant effects on fruit characteristics whereas some GA(3) applications at the blooming period reduced seed numbers and fruit set in considerable amounts. The highest seed numbers per berry were recorded 14.72 from 200 ppm GA(3) and 12.96 from 100 ppm GA(3) applications at bud break stage. On the other hand, average seed numbers per berry were reduced to 3.01, 2.80 and 3.96 by bloom applications of 50, 100 and 200 ppm of GA(3), respectively.

Overexpression of Prunus DAM6 inhibits growth, represses bud break competency of dormant buds and delays bud outgrowth in apple plants.

Most deciduous fruit trees cultivated in the temperate zone require a genotype-dependent amounts of chilling exposure for dormancy release and bud break. In Japanese apricot (Prunus mume), DORMANCY-ASSOCIATED MADS-box 6 (PmDAM6) may influence chilling-mediated dormancy release and bud break. In this study, we attempted to elucidate the biological functions of PmDAM6 related to dormancy regulation by analyzing PmDAM6-overexpressing transgenic apple (Malus spp.). We generated 35S:PmDAM6 lines and chemically inducible overexpression lines, 35S:PmDAM6-GR. In both overexpression lines, shoot growth was inhibited and early bud set was observed. In addition, PmDAM6 expression repressed bud break competency during dormancy and delayed bud break. Moreover, PmDAM6 expression increased abscisic acid levels and decreased cytokinins contents during the late dormancy and bud break stages in both 35S:PmDAM6 and 35S:PmDAM6-GR. Our analysis also suggested that abscisic acid levels increased during dormancy but subsequently decreased during dormancy release whereas cytokinins contents increased during the bud break stage in dormant Japanese apricot buds. We previously revealed that PmDAM6 expression is continuously down-regulated during dormancy release toward bud break in Japanese apricot. The PmDAM6 expression pattern was concurrent with a decrease and increase in the abscisic acid and cytokinins contents, respectively, in dormant Japanese apricot buds. Therefore, we hypothesize that PmDAM6 represses the bud break competency during dormancy and bud break stages in Japanese apricot by modulating abscisic acid and cytokinins accumulation in dormant buds.

Effect of drought stress on shoot growth and physiological response in the cut rose ‘charming black’ at different developmental stages

To investigate the responses of the cut rose ‘Charming Black’ to drought stress at different growth stages, we defined five stages of flowering and shoot development defined from initiation of the axillary bud to full complement of the floral parts. Drought stress was applied from earliest bud break (stage 1) to floral bud appearance (stage 5). After the stage of treatment, irrigation was restored to normal levels. Results showed that rose plant growth was not only influenced by the environment but also by different stages of floral bud appearance. The stem length as well as the time it took to reach different stages of rose development was influenced by the applied irrigation and supplemental lighting conditions. Drought stress did not have negative effects on the quality of the flower at stage 1. Drought stress reduced the vegetative growth phase and promoted flowering in the early stages (2–3), and significantly decreased shoot length, shoot weight and leaf area. However, at the stage prior to flower appearance (stage 5) drought stress was more severe. The most damage was accompanied by malformed floral buds that had shorter petal length and distorted petals. Furthermore, photosynthesis was negatively affected by drought stress at stage 5, even after re-irrigation, for which this negative effect could not be compensated.

Impact of Temperature on Autumn- and Spring-initiated Inflorescence Systems within a Biennial Pruning System of Protea ‘Pink Ice’ Cut Flowers

The potential impact of increasing temperatures driven by climate change on cultivated Protea cut flower production systems is not known. This study used a biennial pruning system in Protea ‘Pink Ice’ to track the physiological and reproductive responses in comparable phenological stages, but exposed to different seasonally determined temperature conditions. Protea ‘Pink Ice’ generally initiates inflorescences terminally on the spring flush. A limited number of shoots can initiate inflorescences on the preceding autumn flush, leading to an advanced harvesting time compared with that of the spring-initiated inflorescences. In a commercial Protea orchard in Hopefield, South Africa, gas exchange, carbohydrate availability, and vegetative and reproductive growth were compared between the two shoot types in the context of seasonal temperature differences. Leaves of shoots, which initiated inflorescences on the autumn flush, generally had higher light-saturated net carbon dioxide (CO2) assimilation capacities in autumn (April–May) and spring (October–November). There is evidence of a requirement of minimum shoot diameter of 7.6 mm (four- or five-flush shoot), as measured directly above the intercalation between the terminal (uppermost mature flush) and subterminal flush, when the subsequent flush was at budbreak stage during April (autumn) and at least five flushes to be required for floral initiation in Protea ‘Pink Ice’. Spring-initiated inflorescences had a shorter developmental period (4 months) than that of autumn-initiated inflorescences (7 months) and developed into significantly smaller (width) inflorescences with a lower width and dry weight at harvest. These inflorescences were harvested on average a month later compared with autumn-initiated inflorescences. The ambient temperature during inflorescence development played a significant role in the inflorescence growth rate, affecting the time required from visible inflorescence detection to harvest. At the calculated optimum base temperature of 9 °C, autumn-initiated inflorescences required 41,010 growing degree hours (GDH), whereas spring-initiated inflorescences required 35,872 GDH from initiation to anthesis. Under future warmer growing conditions, anticipated decreased size and dry weight of inflorescences may reduce marketability and income for Protea producers.

Late spring frost impacts on future grapevine distribution in Europe

Viticulture is a worldwide agricultural sector with a relevant economic importance, especially in regions where the climate and environmental conditions meet requirements for the production of high quality wines. The impact of climate change combined with the increased frequency of extreme events predicted for the next future has already shown its potential detrimental effects on viticulture suitability, but few studies currently explored the effect of long-term climate change and extreme events by considering the inter-varietal variability of grapevine. In this study, the combined effect of mean climate change and extreme events (frost events at budbreak and suboptimal temperatures for fruit-set) under future scenarios (RCP 4.5 and 8.5 for two time slices 2036–2065 and 2066–2095, respectively) was evaluated considering four grapevine varieties with very early, early, middle-early and late phenological cycles. The UniChill model calibrated for these varieties was applied in Europe to assess phenological dynamics (budbreak and flowering) using the outputs of a statistical downscaling procedure. Frost impact around budbreak stage as well as the impact of suboptimal temperature around flowering was estimated under present and future scenarios. The results showed a general earlier occurrence of budbreak and flowering stages with a particular relevance on northeastern Europe. The effect of warmer temperatures had a greater effect on late compared to very early and early varieties in western regions. The frequency of frost events at budbreak (Tmin <0°C) showed wide variability across Europe, with a strong decrease in western regions (e.g. Spain and UK) and an increase in central Europe (e.g. Germany) for future scenarios. The decrease in the frequency of frost events was especially evident for very early and early varieties. The impact of suboptimal temperatures at flowering evidenced a significant variability across a latitudinal gradient while this effect did not show significant results when comparing cultivars and scenarios. The results of these studies highlighted that in a warmer climate frost events rather than stress at flowering will reshape the distribution of grapevine varieties in Europe.

Effects of brassinosteroid (24-epibrassinolide) on yield and quality of grape ("Vitis vinifera" L.) 'Thompson Seedless'

Berry growth ripening process and yield are directly related with nutrition status and phytohormones during fruit growth and development stages. Brassinosteroid (24-epibrassinolide) is one of the plant growth substances that influence different physiological processes including fruit growth and development. In this study, the effect of brassinosteroid (Br) application on the yield and berry quality of 'Thompson Seedless' was investigated in a commercial vineyard, Malayer, Hamedan, Iran. Br solution concentrations of 0, 0.2, 0.4, 0.6 mg·L-1 at five stages (budbreak (S1), prebloom (S2), middle of bloom (S3), post bloom (S4) and veraison (S5) were sprayed. The results showed that the Br application has significant positive effects on bunch morphology and berry quantity and quality. Among levels of Br, the highest yields were related to the application of Br at the rate of 0.6 mg·L-1 in the post bloom and veraison stages, and the lowest was found in the bud break stage. Spraying Br in the post bloom and veraison stages had the greatest effect on berry quality. Also, the highest content of total phenol and antioxidant capacity were obtained with 0.6 mg·L-1 of Br application at veraison stage. In this study, we provided evidence to show that using steroidal plant hormones (Br) may play an essential role in improving the yield and quality of 'Thompson Seedless'.

Molecular Regulation and Substance Exchange Dynamics at Dormancy and Budbreak Stages in Overwintering Buds of Tea Plant

Molecular Regulation and Substance Exchange Dynamics at Dormancy and Budbreak Stages in Overwintering Buds of Tea Plant

Hormonal changes during flowering in response to paclobutrazol application in mango cv. Alphonso under Konkan conditions

Studies were conducted to investigate the effect of soil applied paclobutrazol (PBZ) on the hormonal composition of auxin (IAA), abscisic acid (ABA), cytokinins and gibberellins in 12 years old Alphonso mango trees during the year 2011. Paclobutrazol treatment decreased IAA contain in shoots by 4.3 and 28.2 % at 15 days before bud break and at bud break stage, respectively. Abscisic acid content in PBZ treated trees was 59.85 and 41.11 % higher in leaf and bud, respectively, as compared to untreated trees, during flowering period. Fifteen days before bud break, total cytokinin contents (zeatin, dihydrozeatin riboside, zeatin riboside, isopentenyl adenine, isopentenyl adenosine) in leaf and bud were 25.93 and 37.54 %, respectively less than untreated trees, but at bud break and 15 days after bud break it increased by 31.92 and 36.37 % in leaf and bud, respectively. Paclobutrazol treatment decreased gibberellin contents in shoots. Total gibberellin contents at bud break stage was 51.71 % less in treated trees as compared with untreated trees, while 55.58 % reduction was observed in treated trees from 15 days before bud break to bud break. While in untreated trees slight increment in total gibberellin contents was observed. These results indicated that, PBZ application though decreased gibberellin and IAA contents, but caused increases in ABA and cytokinins in mango shoots to elicit flowering responses.

Response of ‘White Smith’ gooseberry to boron fertilisation under conditions of low soil boron availability

The aim of this study was to examine the effects of different B fertiliser strategies on growth, production and fruit quality of ‘White Smith’ gooseberry (Ribes grossularia L.). The experiment was carried out from 2010 to 2013 on a commercial plantation established in Central Poland in 2006 on a coarse-textured soil with low boron (B) availability. The plants were fertilised with B through: (i) soil application at the bud burst stage at a rate of 1kgha−1, (ii) fertigation over 12 weeks at 7d intervals, beginning at the stage of bud break, at a rate of 0.25kgha−1, (iii) spring sprays at 5–7d before flowering, the beginning of flowering and petal fall at a rate of 0.2kgha−1 in each spray treatment, and (iv) autumn spray at 90d after harvest at a rate of 0.8kgha−1. The plants unfertilised with B served as the control. The results showed that the autumn B spray injured leaves but did not affect defoliation and cold injury of buds. This treatment enhanced autumn leaf B status but had no effect either on the B nutrition of the plants in the following growing season or on the vegetative and reproductive responses of the gooseberries. Spring B sprays were able to increase the flower B concentration, fruit set and yielding but had no impact on the summer and autumn leaf B concentrations. Soil application or fertigation of B increased the soil availability of this nutrient, its status in flowers, summer and autumn leaves, and the activity of glutathione reductase in leaves in the summer and the autumn. Plants supplied with B through soil application or fertigation had higher total lengths of one-year-old shoots, set more fruitlets, and produced more berries. The fruit of those plants also contained more soluble solids and organic acids than those of the control plots. The efficiency of soil application or fertigation of B in improving the reproductive response of gooseberry was higher than that of spring B sprays. No B fertiliser treatment affected the number of buds in terms of meter of shoot or weight of 100 berries. On coarse-textured soils with low B availability, annual fertigation or soil application of B at rates that meet the fertiliser needs of gooseberry in the above fertiliser technologies can be recommended to effectively improve growth, fruit yield, and the processing quality of the fruit.