Bud Break Research Articles

Atmospheric Warming-Associated Phenological Earliness Does Not Increase the Length of Growing Season in Himalayan Trees

Abstract We present phenological data for two time periods (1985–1987 and 2014–2016) on major tree species (Shorea robusta, Pinus roxburghii, Myrica esculenta, Quercus leucotrichophora, Rhododendron arboreum, Quercus floribunda, and Machilus duthiei) occurring along an altitudinal gradient of 300–2,200 m asl of Himalayan forests (a data-deficient region identified by the IPCC, 2007), and show that bud break and leafing in trees has advanced at 0.20 days/year, which is associated with a significant (P < 0.001) increase in atmospheric temperature (0.038°C/year) over the years in the study area. Also, the leaf drop period has advanced correspondingly (0.40 days/year); hence, the length of season (LOS) did not increase in these trees. This finding is contrary to the report of increase in LOS due to climatic warming from temperate latitudes of the world and satellite-based studies in Himalayan region. Arguably, phenomena such as bud break and leafing may not be captured by remote sensing, which is critical for determining the impact of climate change on the forest vegetation of the eco-sensitive Himalayan region. We suggest that this phenological earliness may alter forest structure and functioning and associated ecosystem services of these forests in the long run.

Estimation of Chilling Accumulation for Blackberry (Rubus sp.) Using Mathematical Models

As the climate change takes place, the cultivation of temperate climate crops in subtropical areas has become a challenge. The success of fruit crops, such as blackberry, in certain areas depends basically on its chilling requirement and the chilling accumulation in those areas. Usually the models used to predict those accumulations presents widely variable results being necessary to test the models in the location where the species is cultivated. The objective of this work was to estimate the chilling requirement for bud break of blackberry cultivars Caingangue, BRS Cainguá, Guarani, Tupy, BRS Xavante, BRS Xingu, Brazos, Cherokee and Choctaw, using the models of Utah, Positive Utah, Low Chill, Taiwan, Chilling Hours ≤7.2°C, Chilling Hours ≤11°C, and Dynamic and both temperature and phenological data from 2010 to 2019. The results showed a high variability in cold accumulation for all studied cultivars in all tested models. None of the models performed perfectly to estimate chilling requirement however, the Taiwan and the Utah Positive models can be used to provide a rough estimate of this requirement. On the other hand, Utah and Low Chill models are clearly not suitable for estimating blackberry chilling requirement. The estimated chilling requirement showed that all the studied cultivars are well adapted to the climatic conditions of the southern Rio Grande do Sul, which is emphasized by their good productivity in most of the years.

Dynamics of Diaporthe ampelina Conidia Released from Grape Canes that Overwintered in the Vineyard.

Phomopsis cane and leaf spot (PCLS) is an important disease of grapevines that is mainly caused by Diaporthe ampelina. Dispersal dynamics of D. ampelina spores were investigated in two vineyards, one in northern Italy and one in Montenegro, by using spore samplers that collected α- and β-conidia from rain water running off from PCLS-affected canes. The canes were collected from each vineyard, deployed, and overwintered in the corresponding vineyards. In each of three years (2016, 2017, and 2018), conidial dispersal was investigated during one (Montenegro) or two (Italy) growing seasons following the deployment of the PCLS-affected canes. In the first growing season following cane deployment in both vineyards, α-conidia were mostly found in runoff water after grapevine bud break, especially in April and May, and β-conidia were regularly found in numbers comparable to those of α-conidia, most frequently from June to September. In Italy, high numbers of α- and β-conidia were also collected during the second growing season following cane deployment. The dispersal dynamics of α-conidia over time were described by a Gompertz equation using hydrothermal time (i.e., the accumulated effect of temperature on the maturation rate of pycnidia on days in which the number of hours of wetness was ≥6 or 9 h), with R2 and concordance correlation coefficient >0.9. Rain (≥0.2 mm) was a good predictor of conidial dispersal, with an overall accuracy of 0.97. These results increase our understanding of D. ampelina spore dispersal and should be integrated into warning systems for PCLS management.

Severe frost but not shade could limit the future growing season of Erythronium americanum

Changes in climate are leading to modifications in the timing of seasonal events such as migrations and flowering. Erythronium americanum Ker Gawl. (trout lily) can break bud early in response to warming, but changes to its growing season may be limited by early shade from canopy trees and frost. I experimentally assessed the impact of shade and frost on senescence in E. americanum and descriptively monitored the response of E. americanum to vernal air and soil temperatures in a garden setting. Early shade did not affect the timing of senescence. Experimental exposure to frost resulted in increased leaf damage, earlier senescence, and greater corm death than in control plants. Despite 10 days in which the air temperature dropped below freezing, there was no evidence of leaf damage in the field. These results suggest that early shade from canopy trees will not hasten the end of the future growing season for E. americanum, but that late frost could bring about early senescence if that frost is sufficiently hard.

Endodormancy Release Can Be Modulated by the GA4-GID1c-DELLA2 Module in Peach Leaf Buds.

Gibberellin (GA) plays a key role in the release of bud dormancy and the GA receptor GID1 (GIBBERELLIN INSENSITIVE DWARF1) and DELLA protein are the GA signaling parts, but the molecular mechanism of GA-GID1-DELLA module regulating leaf bud dormancy in peach (Prunus persica) is still not very clear. In this study, we isolated and characterized the GID1 gene PpGID1c from the peach cultivar “Zhong you No.4.” Overexpressing PpGID1c in Arabidopsis promoted seed germination, which indicated that PpGID1c has an important function in dormancy. The expression level of PpGID1c in peach leaf buds during endodormancy release was higher than that during ecodormancy and was positively correlated with GA4 levels. Our study also found that GA4 had the most obvious effect on promoting the bud break, indicating that GA4 may be the key gibberellin to promoting peach leaf bud endodormancy release. Moreover, a quantitative real-time PCR (qRT-PCR) found that GA4 could increase the expression of the gibberellin signaling gene PpDELLA2. A yeast two-hybrid (Y2H) assay suggested that the PpGID1c interaction with the PpDELLA1 protein was not dependent on gibberellin, while the PpGID1c interaction with PpDELLA2 required GA4 or another gibberellin. These findings suggested that the GA4-GID1c-DELLA2 module regulates peach leaf bud endodormancy release, with this finding significantly enhancing our comprehensive understanding of bud endodormancy release and revealing a new mechanism for regulating leaf bud endodormancy release in peach.

Precipitation before Flowering Determined Effectiveness of Leaf Removal Timing and Irrigation on Wine Composition of Merlot Grapevine.

Grapevine productivity, and berry and wine flavonoid concentration, depend on the interactions of cultivar, environment, and applied cultural practices. We characterized the effects that mechanical leaf removal and irrigation treatments had on the flavonoid concentration of ‘Merlot’ (Vitis vinifera, L.) grape berries and wines in a hot climate over two growing seasons with contrasting precipitation patterns. Leaves were removed by machine, either at prebloom (PBLR), or at post-fruit-set (PFLR), or not removed (control) and irrigation was either applied as sustained deficit irrigation (SDI) at 0.8 of crop evapotranspiration (ETc) from budbreak to fruit set, or regulated deficit irrigation (RDI) at 0.8 ETc from bud break to fruit set, 0.5 ETc from fruit set to veraison, and 0.8 ETc from veraison to harvest, of ETc In 2014, PFLR reduced the leaf area index (LAI) compared to control. The RDI decreased season-long leaf water potential (ΨInt) compared to SDI. However, in 2015, none of the treatments affected LAI or ΨInt. In 2014, berry flavonoid concentrations were reduced by PBLR as well as SDI. SDI increased the flavonoid concentrations in wine, and PFLR increased some wine flavonols in one season. No factor affected the concentrations of wine proanthocyanidins or mean degree of polymerization. Thus, mechanical PFLR and RDI may increase berry flavonoid accumulation without yield reduction, in red wine grapes cultivars grown in hot climates when precipitation after bud break is lacking. However, spring precipitation may influence the effectiveness of these practices as evidenced by this work in a changing climate.

Involvement of the auxin\u2013cytokinin homeostasis in adventitious root formation of rose cuttings as affected by their nodal position in the stock plant

Main conclusionEnhanced levels of indole-3-acetic and raised auxin to cytokinin ratios in the stem base contribute to the positive acropetal gradient in rooting capacity of leafy single-node stem cuttings of rose.Cuttings excised from different nodal positions in stock plants can differ in subsequent adventitious root formation. We investigated the involvement of the auxin–cytokinin balance in position-affected rooting of Rosa hybrida. Leafy single-node stem cuttings of two rose cultivars were excised from top versus bottom positions. Concentrations of IAA and cytokinins were monitored in the bud region and the stem base during 8 days after planting using chromatography–MS/MS technology. The effects of nodal position and external supply of indole-butyric acid on rooting were analyzed. Most cytokinins increased particularly in the bud region and peaked at day two before the bud break was recorded. IAA increased in both tissues between day one and day eight. Top versus bottom cuttings revealed higher levels of isopentenyladenosine (IPR) in both tissues as well as higher concentrations of IAA and a higher ratio of IAA to cytokinins particularly in the stem base. The dynamic of hormones and correlation analysis indicated that the higher IPR contributed to the enhanced IAA in the bud region which served as auxin source for the auxin homeostasis in the stem base, where IAA determined the auxin–cytokinin balance. Bottom versus top cuttings produced lower numbers and lengths of roots, whereas this deficit was counterbalanced by auxin application. Further considering other studies of rose, it is concluded that cytokinin-, sucrose- and zinc-dependent auxin biosynthesis in the outgrowing buds is an important factor that contributes to the enhanced IAA levels and auxin/cytokinin ratios in the stem base of apical cuttings, promoting root induction.

High-quality genome assembly of 'Cuiguan' pear (Pyrus pyrifolia) as a reference genome for identifying regulatory genes and epigenetic modifications responsible for bud dormancy

Dormancy-associated MADS-box (DAM) genes serve as crucial regulators of the endodormancy cycle in rosaceous plants. Although pear DAM genes have been identified previously, the lack of a high-quality reference genome and techniques to study gene function have prevented accurate genome-wide analysis and functional verification of such genes. Additionally, the contribution of other genes to the regulation of endodormancy release remains poorly understood. In this study, a high-quality genome assembly for 'Cuiguan' pear (Pyrus pyrifolia), which is a leading cultivar with a low chilling requirement cultivated in China, was constructed using PacBio and Hi-C technologies. Using this genome sequence, we revealed that pear DAM genes were tandemly clustered on Chr8 and Chr15 and were differentially expressed in the buds between 'Cuiguan' and the high-chilling-requirement cultivar 'Suli' during the dormancy cycle. Using a virus-induced gene silencing system, we determined the repressive effects of DAM genes on bud break. Several novel genes potentially involved in the regulation of endodormancy release were identified by RNA sequencing and H3K4me3 chromatin immunoprecipitation sequencing analyses of 'Suli' buds during artificial chilling using the new reference genome. Our findings enrich the knowledge of the regulatory mechanism underlying endodormancy release and chilling requirements and provide a foundation for the practical regulation of dormancy release in fruit trees as an adaptation to climate change.

Molecular responses to chilling in a warming climate and their impacts on plant reproductive development and yield.

Responses to prolonged winter chilling are universal in temperate plants which use seasonal temperature cues in the seed, vegetative and reproductive phases to align development with the earth's orbit. Climate change is driving a decline in reliable winter chill and affecting the sub-tropical extent of cultivation for temperate over-wintering crops. Here we explore molecular aspects of plant responses to winter chill including seasonal bud break and flowering, and how variation in the intensity of winter chilling or de-vernalisation can lead to effects on post-chilling plant development, including that of structures necessary for crop yields.

Thidiazuron with Mineral Oil as Alternative Bud Break Promoter for Apple Trees

Aims: This work aims to evaluate the efficiency of Revent® 500 SC (Thidiazuron) concentrations as a bud breaker promoter in apple trees, cv. Maxi Gala and Supreme Fuji, through phenology, sprouting of buds, fruit set and production per plant.
 Place and Duration of Study: The experiments were carried out in southern Brazil, municipality of Caçador / SC, during the seasons from 2017 to 2019, in the cultivars Fuji Suprema and Maxi Gala / Marubakaido / M9.
 Methodology: The treatments were 1. Control (without application); 2. Mineral Oil (MO) 3.5% + Hydrogenated Cyanamide (HC) 0.35%; 3. MO 3.5% + HC 0.5%; 4. MO 3.5% + Thidiazuron (TDZ) 0.005%; 5. MO 3.5% + TDZ 0.01%; 6. MO 3.5% + TDZ 0.015%; 7.MO 3.5% + TDZ 0.02%; 8.MO 3.5% + TDZ 0.025%, applied in stages B and C. Several variables were evaluated such as phenology, sprouting of axillary and terminal buds, fruit set, production per plant and average fruit mass.
 Results: All treatments with bud breakers advanced the phenological stages in relation to the control in the three years. In the sprouting of the axillary and terminal buds, all treatments were superior to the control. TDZ treatments showed higher sprouting of axillary buds in 2017/18 compared to standard treatments with hydrogenated cyanamide. In plant production, the treatment MO 3.5% + TDZ 0.02% was higher than the other treatments in the 2018/19 and 2019/20 seasons, in both cultivars. TDZ associated with mineral oil is efficient in inducing the sprouting of ‘Maxi Gala’ and ‘Fuji Suprema’ apple trees and can be used to recover sprouts from previous years.

Frost tolerance in apricot (Prunus armeniaca L.) receptacle and pistil organs: how is the relationship among amino acids, minerals, and cell death points?

To the better management of spring frost problem in the apricot cultivars, evaluation of biochemical changes in flower and/or flower organs during bud break could be one of the key factors. In this study, the relationship between the biochemical metabolites such as amino acids and minerals in the receptacle and pistil organs of two different apricot cultivars (frost-sensitive and frost-tolerant) and their relative effects on the frost tolerance of the cultivars and their organs were investigated during full blooming stage. In both apricot cultivars, it was found that the cell death points (CDP) of flower receptacle (- 6.3 to - 8.4°C) were at higher temperatures than the CDP of flower pistil organs (- 13.1 to - 14.5°C). Receptacle organs in flower, therefore, had less tolerance to spring frost damage. In addition, significant differences in mineral and amino acid contents were detected both between apricot cultivars and between the receptacle and pistil organs of the cultivars. Amino acid and mineral contents were lower both in the freezing-sensitive apricot cultivar ("Mihralibey") and the freezing-sensitive organ (receptacle) in comparison with the freezing-tolerant apricot cultivar ("Iğdır Şalak") and the freezing-tolerant organ (pistil). A significant negative correlation was also observed between the mean CDP values and both amino acid and mineral contents in the receptacle and pistil organs of both apricot cultivars. A negative correlation was found between CDP values and glutamate from amino acids and N, K, and Mg from minerals, and also these were determined that they had positive effects on frost tolerance increase. An important finding from our work revealed that the amount of each mineral and amino acid allocated differently to the receptacle and pistil organs of the apricot cultivars. The understanding of the amino acids and the mineral dynamics may contribute to improving the tolerance of flowers of apricot or other deciduous species to frost damage during spring. In the future, we may conclude that protection strategies such as increasing amino acids and mineral content in the receptacle organ of flowers would be necessary to cope with the negative effects of spring frost.

Deacclimation and reacclimation of apple (Malus × domestica Borkh.), blackcurrant (Ribes nigrum L.) and raspberry (Rubus idaeus L.) shoots and buds under controlled conditions

In the future climate scenario the transient warm spells during winter are predicted to become more frequent and potentially increase the risk of frost damage in perennial horticultural crops. The aim of our study was to examine, whether apple (Malus × domestica Borkh.), blackcurrant (Ribes nigrum L.), and raspberry (Rubus idaeus L.) cultivars differing in winter hardiness have a different susceptibility to deacclimation during a warm spell and the ability to reacclimate in response to a subsequent cold period. Shoot samples were collected from commercial orchards in Finland on Feb. 6, 2019. Samples were subjected to a deacclimation treatment (+5°C, 4 d) followed by a reacclimation treatment (-7°C, 7 d). Controlled freezing tests were conducted immediately after sampling, and at the end of deacclimation and reacclimation treatments to determine frost hardiness (FH). FH was most stable in those cultivars that are known to be hardy in the Finnish climate conditions, i.e. ‘Pirja’ apple, ‘Mikael’ and ‘Öjebyn’ blackcurrants, and ‘Maurin Makea’ raspberry. Buds were consistently less hardy than shoots, the difference being largest in blackcurrant, 25°C. The buds of all cultivars, except ‘Pirja’ apple, deacclimated during four days at +5°C, but only ‘Ben Tron’ blackcurrant buds were able to reacclimate. The depth of dormancy was determined by forcing the shoot samples in a greenhouse to examine the relationship of the FH stability to the dormancy status in the cultivars. Sixty to 95 % of apple, 98 to 100 % of blackcurrant, and 55 to 67 % of raspberry buds broke during five weeks in forcing. Only the apple cultivars exhibited cultivar differences in the dormancy status in the beginning of February. ‘Pirja’ despite having the most stable FH of the apple cultivars, showed the most complete and fastest bud break in forcing. Consequently, the susceptibility to deacclimation during a warm spell and the ability to reacclimate at subsequent low temperatures were not related to the status of dormancy in these cultivars.

A single out-of-season fungicide application reduces the grape powdery mildew inoculum

Strategies for the control of grape powdery mildew, caused by Erysiphe necator, Schw., require consideration of the development of fungicide resistance. We investigated the effect of inoculum reduction by fungicides with low resistance risk (copper oxychloride, potassium bicarbonate, meptyldinocap, wettable sulphur) in the laboratory and as individual post-harvest and bud break treatments. Ascospore viability and release were analysed after a post-harvest treatment and disease incidence and severity of grapes were determined following a bud break treatment. In the laboratory all fungicides reduced the viability (spring 2018 p = 0.008; autumn 2018 p = 0.021; spring 2019 p = 0.010; autumn 2019 p = 0.484) and the release (spring 2018 p = 0.007; autumn 2018 < 0.001; spring 2019 < 0.001) of ascospores, although the decrease was more pronounced in spring compared to autumn. At Krems, the post-harvest field application of copper oxychloride, potassium bicarbonate, meptyldinocap and wettable sulphur in autumn 2017 reduced the percentage of viable chasmothecia significantly (p < 0.001) by 56–74%. In autumn 2018, the tested fungicides had no effect on the percentage of viable chasmothecia (p = 0.129). At Andau, the percentage of viable chasmothecia was only reduced by copper oxychloride (p = 0.029). The amount of viable ascospores was significantly (p = 0.002) lowered after a post-harvest field treatment with the fungicides by 46–70%, whereas for meptyldinocap only a trend could be determined. Disease incidence and severity were not influenced by sulphur applications at bud break (p = 0.689, p = 0.224) and by different levels of chasmothecia (p = 0.104, p = 0.353). A trend in one year, that a high amount of chasmothecia increased the disease incidence, was related to the weather conditions and the duration from the time of first ascosporic infection until flowering. The data indicates the importance of an effective control with fungicides during the pre-flowering stage in years with a long time from primary infection until flowering. Furthermore, this study shows that post-harvest sprays with low risk fungicides can help to reduce the number of fungicide treatments needed for powdery mildew control at the end of the in-season spray program. This measure could be integrated into an environmentally friendly pesticide reduction program for controlling powdery mildew in viticulture.

Integrating Genome-Wide Association Analysis With Transcriptome Sequencing to Identify Candidate Genes Related to Blooming Time in Prunus mume.

Prunus mume is one of the most important woody perennials for edible and ornamental use. Despite a substantial variation in the flowering phenology among the P. mume germplasm resources, the genetic control for flowering time remains to be elucidated. In this study, we examined five blooming time-related traits of 235 P. mume landraces for 2 years. Based on the phenotypic data, we performed genome-wide association studies, which included a combination of marker- and gene-based association tests, and identified 1,445 candidate genes that are consistently linked with flowering time across multiple years. Furthermore, we assessed the global transcriptome change of floral buds from the two P. mume cultivars exhibiting contrasting bloom dates and detected 617 associated genes that were differentially expressed during the flowering process. By integrating a co-expression network analysis, we screened out 191 gene candidates of conserved transcriptional pattern during blooming across cultivars. Finally, we validated the temporal expression profiles of these candidates and highlighted their putative roles in regulating floral bud break and blooming time in P. mume. Our findings are important to expand the understanding of flowering time control in woody perennials and will boost the molecular breeding of novel varieties in P. mume.

GA3 is superior to GA4 in promoting bud endodormancy release in tree peony (Paeonia suffruticosa) and their potential working mechanism

BackgroundSufficient low temperature accumulation is the key strategy to break bud dormancy and promote subsequent flowering in tree peony anti-season culturing production. Exogenous gibberellins (GAs) could partially replace chilling to accelerate dormancy release, and different kinds of GAs showed inconsistent effects in various plants. To understand the effects of exogenous GA3 and GA4 on dormancy release and subsequent growth, the morphological changes were observed after exogenous GAs applications, the differentially expressed genes (DEGs) were identified, and the contents of endogenous phytohormones, starch and sugar were measured, respectively.ResultsMorphological observation and photosynthesis measurements indicated that both GA3 and GA4 applications accelerated bud dormancy release, but GA3 feeding induced faster bud burst, higher shoot and more flowers per plant. Full-length transcriptome of dormant bud was used as the reference genome. Totally 124 110 459, 124 015 148 and 126 239 836 reads by illumina transcriptome sequencing were obtained in mock, GA3 and GA4 groups, respectively. Compared with the mock, there were 879 DEGs and 2 595 DEGs in GA3 and GA4 group, 1 179 DEGs in GA3 vs GA4, and 849 DEGs were common in these comparison groups. The significant enrichment KEGG pathways of 849 DEGs highlighted plant hormone signal transduction, starch and sucrose metabolism, cell cycle, DNA replication, etc. Interestingly, the contents of endogenous GA1, GA3, GA4, GA7 and IAA significantly increased, ABA decreased after GA3 and GA4 treatments by LC–MS/MS. Additionally, the soluble glucose, fructose and trehalose increased after exogenous GAs applications. Compared to GA4 treatment, GA3 induced higher GA1, GA3 and IAA level, more starch degradation to generate more monosaccharide for use, and promoted cell cycle and photosynthesis. Higher expression levels of dormancy-related genes, TFL, FT, EBB1, EBB3 and CYCD, and lower of SVP by GA3 treatment implied more efficiency of GA3.ConclusionsExogenous GA3 and GA4 significantly accelerated bud dormancy release and subsequent growth by increasing the contents of endogenous bioactive GAs, IAA, and soluble glucose such as fructose and trehalose, and accelerated cell cycle process, accompanied by decreasing ABA contents. GA3 was superior to GA4 in tree peony forcing culture, which might because tree peony was more sensitive to GA3 than GA4, and GA3 had a more effective ability to induce cell division and starch hydrolysis. These results provided the value data for understanding the mechanism of dormancy release in tree peony.

Plant phenological responses to experimental warming-A synthesis.

Although there is abundant evidence that plant phenology is shifting with climatic warming, the magnitude and direction of these shifts can depend on the environmental context, plant species, and even the specific phenophase of study. These disparities have resulted in difficulties predicting future phenological shifts, detecting phenological mismatches and identifying other ecological consequences. Experimental warming studies are uniquely poised to help us understand how climate warming will impact plant phenology, and meta-analyses allow us to expose broader trends from individual studies. Here, we review 70 studies comprised 1226 observations of plant phenology under experimental warming. We find that plants are advancing their early-season phenophases (bud break, leaf-out, and flowering) in response to warming while marginally delaying their late-season phenophases (leaf coloration, leaf fall, and senescence). We find consistency in the magnitude of phenological shifts across latitude, elevation, and habitat types, whereas the effect of warming on nonnative annual plants is two times larger than the effect of warming on native perennial plants. Encouragingly for researchers, plant phenological responses were generally consistent across a variety of experimental warming methods. However, we found numerous gaps in the experimental warming literature, limiting our ability to predict the effects of warming on phenological shifts. In particular, studies outside of temperate ecosystems in the Northern Hemisphere, or those that focused on late-season phenophases, annual plants, nonnative plants, or woody plants and grasses, were underrepresented in our data set. Future experimental warming studies could further refine our understanding of phenological responses to warming by setting up experiments outside of traditionally studied biogeographic zones and measuring multiple plant phenophases (especially late-season phenophases) across species of varying origin, growth form, and life cycle.

Climate-driven divergence in plant-microbiome interactions generates range-wide variation in bud break phenology

Soil microbiomes are rapidly becoming known as an important driver of plant phenotypic variation and may mediate plant responses to environmental factors. However, integrating spatial scales relevant to climate change with plant intraspecific genetic variation and soil microbial ecology is difficult, making studies of broad inference rare. Here we hypothesize and show: 1) the degree to which tree genotypes condition their soil microbiomes varies by population across the geographic distribution of a widespread riparian tree, Populus angustifolia; 2) geographic dissimilarity in soil microbiomes among populations is influenced by both abiotic and biotic environmental variation; and 3) soil microbiomes that vary in response to abiotic and biotic factors can change plant foliar phenology. We show soil microbiomes respond to intraspecific variation at the tree genotype and population level, and geographic variation in soil characteristics and climate. Using a fully reciprocal plant population by soil location feedback experiment, we identified a climate-based soil microbiome effect that advanced and delayed bud break phenology by approximately 10 days. These results demonstrate a landscape-level feedback between tree populations and associated soil microbial communities and suggest soil microbes may play important roles in mediating and buffering bud break phenology with climate warming, with whole ecosystem implications.

STRATEGY FOR COMBATING BACTERIAL BURN OF FRUIT CROPS IN KAZAKHSTAN

On the basis of many years of research, a strategy for combating fire blight was developed, including a set of measures aimed at reducing the infectious load in gardens, curbing the intensity of pathogen reproduction, and increasing plant resistance to disease. On the basis of this strategy, a complex of control measures was developed, including the autumn pruning of affected organs in accordance with quarantine requirements, whitewashing of trunks and skeletal branches with lime with the addition of 4 % copper sulfate and spraying with the fungicide Cosside 2000, v.d. (3 kg/ha); in the spring, prophylactic spraying with the same fungicide before bud break; during the flowering period, double spraying with biological preparations of Fitolavin, VRK (2 l/ha); after flowering, during the period of ovary abscission, double spraying with growth regulator Regalis plus (d.v. prohexadione calcium), 1,25 kg/ha. A production test has shown that complex measures developed on the basis of a fire blight control strategy effectively suppress the disease at the site of infection. The biological efficiency was 97.5 % with an increase in yield 36.2 %.

An empirical method to account for climatic adaptation in plant phenology models.

Phenological shifts in plant species are one of the most conspicuous signs of climate change impact on the biosphere. Modeling phenological variations of plant species over broad regions is challenging because of the varied climatic requirements of geographic populations due to local adaptation. In this study, we developed an empirical method to calibrate phenological models of temperate trees using latitude as a predictor to account for local adaptation of populations to a N-S temperature gradient. Fourteen widely distributed tree species in the eastern U.S.A. were investigated using data from the USA-National Phenology Network. We implemented the method in a basic thermal time bud break model to introduce the algorithm of the method and test its effectiveness. For each species, dates of breaking leaf buds were first predicted using a traditional non-spatial model and then with a spatial model that has the critical thermal forcing requirements calibrated for different populations at varied latitudes. As anticipated, non-spatial model predictions that assumed a uniform forcing requirement across latitudes showed consistent and systematic biases at both higher (overestimation-predictions being later) and lower (underestimation-predictions being earlier) latitudes. Spatial models that have been calibrated using our method removed the geographic biases and yielded latitudinal gradients that more closely matched those of the observations. The spatial models also reduced the overall prediction errors from an average root mean square error (RMSE) of 32.2 days to 20.4 days for the training dataset and an average root mean square error for prediction (RMSEP) of 32.2 days to 19.9 days for the testing dataset. This paper is focused on introducing the new calibration method as a preparatory step toward developing operational models that may potentially predict large-scale and range-wide phenological responses of various plant species to climatic changes with improved local accuracy.

Overexpression of a SOC1-Related Gene Promotes Bud Break in Ecodormant Poplars.

Perennial species in the boreal and temperate regions are subject to extreme annual variations in light and temperature. They precisely adapt to seasonal changes by synchronizing cycles of growth and dormancy with external cues. Annual dormancy–growth transitions and flowering involve factors that integrate environmental and endogenous signals. MADS-box transcription factors have been extensively described in the regulation of Arabidopsis flowering. However, their participation in annual dormancy–growth transitions in trees is minimal. In this study, we investigate the function of MADS12, a Populus tremula × alba SUPPRESSOR OF CONSTANS OVEREXPRESSION 1 (SOC1)-related gene. Our gene expression analysis reveals that MADS12 displays lower mRNA levels during the winter than during early spring and mid-spring. Moreover, MADS12 activation depends on the fulfillment of the chilling requirement. Hybrid poplars overexpressing MADS12 show no differences in growth cessation and bud set, while ecodormant plants display an early bud break, indicating that MADS12 overexpression promotes bud growth reactivation. Comparative expression analysis of available bud break-promoting genes reveals that MADS12 overexpression downregulates the GIBBERELLINS 2 OXIDASE 4 (GA2ox4), a gene involved in gibberellin catabolism. Moreover, the mid-winter to mid-spring RNAseq profiling indicates that MADS12 and GA2ox4 show antagonistic expression during bud dormancy release. Our results support MADS12 participation in the reactivation of shoot meristem growth during ecodormancy and link MADS12 activation and GA2ox4 downregulation within the temporal events that lead to poplar bud break.