Studies on Mode of Expression of Apple （Malus x domestica Borkh.） Bud Dormancy under Tropical and Temperate Climatic Conditions

A study was conducted to describe the progression of bud dormancy in 1-year-old apple （Malus x domestica Borkh） shoots grown at two contrasting climatic conditions （Belgium, temperate and Ethiopia, tropics）. The experiment was carried out on ＂Golden＂ and ＂Gala＂ cultivars for two consecutive years （2010/2011 and 2011/2012）. Moreover, a validation experiment was conducted on ＂MM106＂ apple rootstock during 2010/2011 only in Ethiopia. Variations in inverse of time to 50% budburst were interpreted in terms of evolution of growth capacity of the buds. Despite differences observed with chilling accumulation later in winter or early in spring, depending on environments, depth of endodormancy intensity during winter can be summarized as follows： buds from pruned shoots were less endodormant than terminal buds of the intact shoots and terminal buds were more endodormant than the dormancy intensity of upper buds of the disbudded shoots, suggesting proximal buds can grow more readily than does terminal ones. Our results provide evidence for the existence of a considerably strong paradormancy inhibition by distal shoot parts and buds, which was more pronounced in Ethiopia than in Belgium, highlighting the importance of designing and applying appropriate pruning and dormancy avoidance strategies in mild-winter climates. Finally, as still there is knowledge gap on bud dormancy progression and its control mechanism especially under mild climates, our study highlights the need for further in-depth research using biological and biochemical tests.

Resistance index and browning mechanism of apple peel under high temperature stress

Apples are one of the most important economic crops worldwide.Because of global warming and an aggravation of environmental,abnormally high temperatures occur frequently in fruit-growing season and seriously affect normal fruit growth and reduce fruit quality and yield.We took five-year-old Ruixue’(Qinfu 1×Pink Lady;CNA20151469.1) fruits as test materials,and the ambient temperature during fruit development was monitored.The results showed that during the fruit-growing season,especially during the rapid growth stage (July to August),the maximum daily temperature exceeded 30℃ and lasted for more than 40 days.To determine the effects of high temperature stress on the apple fruit resistance,we treated expanding,veraison,and maturity-period fruits at different temperatures.It was found that the fruits of the expanding period showed strong resistance to high temperature stress,whereas during veraison and maturity,fruit resistance to high temperature stress decreased,and the fruit peel browning phenotype appeared.Meanwhile,the content of malonaldehyde (MDA),hydrogen peroxide (H_(2)O_(2)),and superoxide anion (O._(2)^(-)) in the peel gradually increased with increasing temperature.The content of total phenols,flavanol,and flavonoids in the peel decreased substantially at 45℃.Moreover,it was found that polyphenol oxidase gene (MdPPO1) was most sensitive to high temperature stress in apple.Furthermore,transient and stable MdPPO1 overexpression significantly promoted peel browning.The transgenic materials were more sensitive to high temperatures,and browning was more severe compared to non-genetically modified organism (WT).Stable MdPPO1 knockout calli obtained via clustered regularly interspersed short palindromic repeats (CRISPR/Cas9) gene knockout technology reduced the browning phenotype,and the resultant fruits were not sensitive to the effects of high temperature stress.Thus,MdPPO1 expression may be a key factor of high temperature-related changes observed in the browning phenotype that provides a scientific theoretical basis for the selection of high temperature-resistant varieties and apple cultivation and management in the future.

Comparison of cell wall changes of two different types of apple cultivars during fruit development and ripening

Fruit development and ripening is a complex procedure(Malus×domestica Borkh.)and can be caused by various factors such as cell structure,cell wall components,and cell wall hydrolytic enzymes.In our study,we focused on the variations in fruit firmness,cell wall morphology and components,the activity of cell wall hydrolytic enzymes and the expression patterns of associated genes during fruit development in two different types of apple cultivars,the hard-crisp cultivar and the loose-crisp cultivar.In this paper,the aim was to find out the causes of the texture variations between the different type cultivars.Cell wall materials(CWMs),hemicellulose and cellulose content were strongly associated with variations in fruit firmness during the fruit development.The content of water soluble pectin(WSP)and chelator soluble pectin(CSP)gradually increased,while the content of ionic soluble pectin(ISP)showed inconsistent trends in the four cultivars.The activities of polygalacturonase(PG),β-galactosidase(β-gal),cellulase(CEL),and pectate lyase(PL)gradually increased in four cultivars.And the activities of PG,β-gal,and CEL were higher in‘Fuji’and‘Honeycrisp’fruit with the fruit development,while the activity of PL of‘Fuji’and‘Honeycrisp’was lower than that of‘ENVY’and‘Modi’.Both four cultivars of fruit cells progressively became bigger as the fruit expanded,with looser cell arrangements and larger cell gaps.According to the qRT-PCR,the relative expression levels of MdACO and Mdβ-gal were notably enhanced.Our study showed that there were large differences in the content of ISP and hemicellulose,the activity of PL and the relative expression of Mdβ-gal between two different types of apple cultivars,and these differences might be responsible for the variations in the texture of the four cultivars.

Overexpression of MdFRK2 enhances apple drought resistance by promoting carbohydrate metabolism and root growth under drought stress

Soluble sugars function not only as the energy and structural blocks supporting plants,but also as osmoregulators and signal molecules during plant adaptation to water deficit.Here,we investigated drought resistance in transgenic apple(Malus×domestica)overexpressing MdFRK2,a key gene regulating fructose content and sugar metabolism.There is no obvious phenotypic difference between MdFRK2-overexpressing transgenic plants and WT plants under the well-watered condition.However,the transgenic plants and the grafted plants using MdFRK2-overexpressing rootstock exhibited improved tolerance to drought stress.Overexpression of MdFRK2 significantly promoted the growth of root system under drought stress.RNA sequencing showed that under drought stress,genes involved in sugar metabolism,transcription regulation,signal transduction or hormone metabolism were differentially expressed in MdFRK2 transgenic plants.Consistent with the gene expression profile,the activities of enzyme(SDH,FRK and NI)involved in sugar metabolism in the roots of MdFRK2 transgenic plants were significantly higher than those of untransformed control plants after drought stress.Under drought stress,overexpression of MdFRK2 promoted the accumulation of IAA,and decreased the contents of ABA and CK in apple root system.In conclusion,these results suggest that MdFRK2 can promote the growth of apple roots under drought stress by regulating sugar metabolism and accumulation,hormone metabolism and signal transduction,and then resist drought stress.

Isolation of phloridzin-degrading,IAA-producing bacterium Ochrobactrum haematophilum and its effects on the apple replant soil environment

We isolated and identified a bacterium that could produce IAA and degrade phloridzin in the rhizosphere soil of healthy replanted apple(the rootstock is M9T337 and the scion is Yanfu 3),providing a theoretical basis for reducing the obstacles associated with apple replant disease(ARD).Isolates were screened using Salkowski colorimetry and screening medium for phloridzin.The isolate of interest(W6)was identified as Ochrobactrum haematophilum based on morphological analysis,physiological and biochemical tests,and 16S rDNA sequencing.In a laboratory experiment,W6 produced auxin and promoted the growth of Arabidopsis thaliana roots,and its degradation rate of 100 mg.L^(-1 )phloridzin was 62.0%.In a pot experiment,W6 significantly reduced the phenolic acid contents of replanted soil,lowered the abundance of the harmful fungus Fusarium solani,and increased soil enzyme activities,thereby improving the micro-ecological environment of replant soil.W6 increased the root antioxidant enzyme activity and leaf photosynthetic pigment content of replanted Malus hupehensis Rehd.seedlings,effectively alleviating the decrease in net photosynthetic rate,transpiration rate and stomatal conductance caused by ARD.In a field experiment,W6 also promoted the growth of replanted apple(the rootstock is M9T337 and the scion is Yanfu 3)saplings.Therefore,W6 can promote apple growth and degrade phenolic acids,and it can be used as an effective treatment for the reduction of ARD.

Genome-wide identification of apple auxin receptor family genes and functional characterization of MdAFB1

The auxin receptor(TIR1/AFBs)family encodes the F-box protein subunit,which is involved in the formation of the E3 ubiquitin ligase SCFTIR1/AFBs complex,a key component of the auxin signaling pathway.However,there are few studies on the auxin receptor family in apple(Malus×domestica).In this study,eight MdAFBs were identified,and phylogenetic analysis showed that they were classified into four groups and distributed on eight chromosomes.Herein,a comprehensive analysis of the MdAFB gene family was conducted to identify cis-acting elements,gene structures,protein structures,aligned sequences,conserved motifs,conserved amino acids,and the protein–protein interaction network.The results of yeast two-hybrid assays showed that MdAFB1 interacted with three auxin repressor proteins.The results of qRT-PCR showed that MdAFB1 responded to osmotic and salt stress.The overexpression of MdAFB1 increased osmotic and salt resistance in apple calli,and the ectopic expression of MdAFB1 enhanced osmotic and salt tolerance in Arabidopsis.This study provided a basis for the identification of auxin receptor genes in apple and their functions in mediating osmotic and salt stress.

Inheritance and Molecular Marker of Resistance to Bot Canker in Malus domestica

Apple bot canker [Botryosphaeria dothidea（Moug.） Ces.et de Not.] is distributed worldwide,resulting in a serious crop loss every year in apple（Malus domestica Borkh.） production.The resistance of each seedling derived from a hybrid population（Jonathan×Golden Delicious） was evaluated by disease index either from natural infection in the field or from inoculation with five isolates of B.dothidea,Ls1,Lw023,Lw048,Mx1,and Zz26.The inheritance of the resistance to bot canker was analyzed via frequency distribution analysis,and microsatellite and AFLP markers linked to the resistance loci were screened.From the binary frequency distribution patterns,it was found that the segregation ratio of resistant/susceptible genotypes infected by pathogen isolates Lw023 and Ls1 was 1：15;and that by Zz26 and Mx1 was 15：1.The variation of resistance was involved in the segregation of two to four alleles of major genes,the resistance was recessive when infected by Lw023 and Ls1,but was dominant when infected with Mx1 and Zz26.A microsatellite maker,CH02a04-450,and two AFLP markers,E-AG/M-GAC-280 and E-AGG/M-CTT-110,were identified,and their map distances to the resistance loci were 5.1,5.1 and 6.2 cM,respectively.The three markers are located in different linkage groups,while CH02a04-450 is on linkage group 2 or 7.E-AG/M-GAC-280 was successfully converted into SCAR159.Finally,CH02a04-450 and SCAR159 were re-examined in inoculated segregation population and presented a good reliability on predicting phenotypes of resistance.

MdWRKY75e enhances resistance to Alternaria alternata in Malus domestica

The Alternaria alternata apple pathotype adversely affects apple(Malus domestica Borkh.)cultivation.However,the molecular mechanisms underlying enhanced resistance to this pathogen in apple remain poorly understood.We have previously reported that MdWRKY75 expression is upregulated by A.alternata infection in‘Sushuai’apples.In this study,we discovered that overexpression of MdWRKY75e increased the resistance of transgenic apple lines to A.alternata infection,whereas silencing this gene enhanced susceptibility to A.alternata infection.Furthermore,we found that MdWRKY75e directly binds to the MdLAC7 promoter to regulate the biosynthesis of laccase and increase the biosynthesis of lignin during A.alternata infection.Moreover,the thickening of the cell wall enhanced the mechanical defense capabilities of apple.In addition,we found that jasmonic acid remarkably induced MdWRKY75e expression,and its levels in transgenic apple lines were elevated.These results indicate that MdWRKY75e confers resistance to the A.alternata apple pathotype mainly via the jasmonic acid pathway and that pathogenesis-related genes and antioxidant-related enzyme activity are involved in the disease resistance of MdWRKY75e transgenic plants.In conclusion,our fi ndings provide insights into the importance of MdWRKY75e for resistance to A.alternata infection in apples.

Malus domestica and Solanum lycopersicum Mixtures for the Synthesis of Graphene Silver and Zinc Oxide Nanocomposites

This study reports on the novel and simple green method involving the use of apple (Malus domestica) and tomato (Solanum lycopersicum) extracts in the synthesis of electroactive layers of silver nanoparticles|graphene oxide (AgNPs|GO) and zinc oxide nanoparticles|graphene oxide (ZnONPs|GO). The surface morphology of the green synthesized nanocomposites was studied using High-Resolution Transmission Electron Microscopy (HRTEM), High-Resolution Scanning Electron Microscopy (HRSEM) while the elemental analysis was studied using Fourier Transform Infrared Spectroscopy (FTIR), Raman spectroscopy and X-Ray diffraction (XRD) and their optical properties were further characterised using Ultraviolet Spectroscopy (UV-vis). The electrochemical studies of these nanocomposites were achieved using cyclic voltammetry (CV) where an increase in electron conductivity of the AgNPs|GO and ZnONPs|GO nanocomposite was observed. Comparatively, the silver nanoparticulate-based platforms were observed to have superior electrochemical properties as opposed to the zinc oxide-based platform. The observed electrochemical activities of the synthesized nanocomposites are a good indication of their suitability as electroactive platforms towards the development of electrochemical sensors. Electrochemical sensors are popular in the Electrochemistry field because they may be developed using different methods in order to suit their intended analytes. As such, the synthesis of a variety of electrochemical platforms provides researchers with a vast range of options to select from for the detection of analytes.

新疆野生苹果(Malus sieversii)的总多酚、总黄酮提取物的抗氧化活性研究

以采集于新疆不同地区的20个野生苹果品种为研究对象,福林酚法测总多酚,分光光度计法测定总黄酮,DPPH、ABTS、还原能力法测定总抗氧化能力,相关系数法分析各个指标之间的相关性。结果显示,不同品种的野生苹果的总多酚、总黄酮及抗氧化活性之间具有显著差异,其中,HDM-23的总多酚含量最高(4714.33μmol没食子酸/100g鲜果),XY-31的总黄酮含量最高(2452.84mg芦丁/100g鲜果)。总多酚、总黄酮及抗氧化活性之间呈极显著(p<0.01)正相关,表明总多酚与总黄酮是野生苹果抗氧化活性的主要贡献物质。

The Relation Between Endogenous Hormones and Late-Germination in Buds of Avrolles Apple

In order to provide the physiological bases for selecting late-germination cultivars that can avoid late frost damage, the very late-germination variety Avrolles （Malus domestica） was used to study the relation between the dynamic changes and balance of endogenous hormones and germination time. The concentrations of endogenous GA3, ABA, IAA, and ZR were determined in buds of Avrolles and Judeline （Malus domestica） from dormancy releasing to germination by capillary electrophoresis. The dynamic changes of endogenous hormones concentration in buds of Avrolles and Judeline were similar; but the magnitude and time of the change were significantly different between the two varieties, especially for GA3. GA3 concentration increased with dormancy releasing, then decreased, and increased again before germination in the two varieties. GA3 concentration in Avrolles was 1.72 times that in Judeline at the first peak, the gap increased to 2.22 times at germination. ZR concentration exhibited a continuous increase trend, but it decreased sharply before germination. ZR accumulation in Avrolles took 36 days longer than in Judeline, the peak value was 44% higher than in Judeline. Before germination, ZR concentration in Avrolles was 2.12 times that in Judeline. The differences between IAA and ABA concentration were relatively small in the two varieties, while the ratios of GA3/ABA and （GA3 ＋ IAA ＋ ZR）/ABA in Avrolles were 2.08 and 1.58 times those in Judeline, respectively. The germination of apple bud was regulated by the endogenous hormones. For the late-germination apple Avrolles, its germination requires higher concentration of GA3 and ZR, which leads to the high ratios of GA3/ABA and （GA3＋ IAA＋ ZR）/ABA.

Genome-wide identification and expression analysis of asparagine synthetase family in apple

Asparagine is an efficient nitrogen transport and storage carrier. Asparagine synthesis occurs by the amination of aspartate which is catalyzed by asparagine synthetase(ASN) in plants. Complete genome-wide analysis and classifications of the ASN gene family have recently been reported in different plants. However, systematic analysis and expression profiles of these genes have not been performed in apple(Malus domestica). Here, a comprehensive bioinformatics approach was applied to identify MdASNs in apple. Then, plant phylogenetic tree, chromosome location, conserved protein motif, gene structure, and expression pattern of MdASNs were analyzed. Five members were identified and distributed on 4 chromosomes with conserved GATase-7 and ASN domains. Expression analysis indicated that all MdASNs mRNA accumulated at the highest level in reproductive organs, namely flowers or fruits, which may be associated with the redistribution of free amino acids in plant metabolic organs and reservoirs. Additionally, most of Md ASNs were dramatically up-regulated under various nitrogen supplies, especially in the aboveground part. Taken together, MdASNs may be assigned to be responsible for the nitrogen metabolism and asparagine synthesis in apple.

The effects of crop rotation combinations on the soil quality of old apple orchard

This study investigated the effects of six crop rotation combinations on the soil quality of old apple orchard and seedling growth of Malus hupehensis Rehd.(apple rootstock) under pot conditions. The inhibitory effects of crops such as Allium fistulosum, Brassica juncea, and Triticum aestivum on four species of Fusarium were observed and compared in six treatments. These were continuous cropping(CK), fumigation with the methyl bromide(FM), rotating A. fistulosum only(R1), rotating A. fistulosum and T. aestivum(R2), rotating A. fistulosum, B. juncea, and T. aestivum(R3), and fallow(FC) in a year. The results showed that the biomass of Malus hupehensis Rehd. seedlings increased significantly. The root length increased and the root architecture was optimized. The respiration rate of the root system was increased by about 1 time after rotation. The treatments of R1, R2, R3, and FC increased bacterial count by 232.17%, 96.04%, 316.21%, and 60.02%, respectively. However, the fungi were reduced in varying degrees and bacteria/fungi ratio was increased by 5–10 times. The enzyme activities, p H, and organic matter were increased, but soil bulk density was decreased. Phenolic acids such as phloridzin was decreased significantly. The copy number of four Fusarium species declined by 85.59%, 74.94%, 69.68%, and 54.41% after rotating three different crops(R3 treatment). The root volatiles of three plants inhibited mycelial growth and spore germination of four Fusarium species.

Phytopigments, Proline, Chlorophyll Index, Yield and Leaf Nitrogen as Impacted by Rootstock, Training System, and Girdling in “Aztec Fuji” Apple

World overpopulation, scarcity of water and finite arable land mandate a more efficient use of these natural resources. To remain sustainable, modern-day apple (Malus domestica Borkh.) fruit production utilizes high-density orchards on semi-dwarfing, precocious rootstocks. Nonetheless, little attention has been paid to the use of size-controlling practices such as trunk girdling in these modern orchard systems. The impact of two rootstocks, two tree architecture (training) systems, and three levels of girdling (in spring) on chlorophyll index (CI), proline, chlorophyll content (Chl;a, b, a + b), carotenoids, anthocyanin, yield, fruit weight and leaf nitrogen (N) in “Aztec Fuji” were studied in 2015 and 2016. Trees on “Bud 9” had up to 5% higher chlorophyll indices in leaves on side branches than those on “Nic 29” at each sampling time in 2015 and 2016. However, trees on “Nic 29” had up to 5.5% chlorophyll index in terminal branches, 14% higher Chl b, 54% higher leaf proline in 2015, up to 5% higher leaf nitrogen (N) in 2015 and 2016, 82% higher yields in 2015, and up to 7% higher fruit weight in 2015 and 2016 than those on “Bud 9”. Trees trained into a central leader (CL) architecture had up to 6% higher chlorophyll index and 4% higher leaf N in terminal branches 2015 and 2016, 43% more terminal leaf proline content in 2015, but 13% less yield in 2016 than those with a tall spindle training (TS). Terminal leaves from trees receiving a bark girdling in 2015 (BG15) had up to 6.5% lower leaf N, 7% less chlorophyll index, and between 27% to 56% lower proline content than those from the ungirdled check and score girdled treatment in 2015 (SG15). Also, trees with BG15 and a bark girdling in both 2015 and 2016 (BG1516) treatments had significantly less leaf N concentration than all other treatments or the ungirdled check. Trees that were score girdled in 2015 and repeat score girdled in 2016 (SG1516) had 21% higher yield and 12% higher fruit weight than those that were ungirdled.

Evaluation of Minimally Processed Apples with Application of Edible Films through Biospeckle

The search for practical eating has been increasing among consumers. Thus, minimally processed （MP） foods, which are fresh, previously cut, washed, sanitized and packed products, may be covered with films so as to keep their quality, reducing the deterioration processes. This paper aimed to evaluate the quality of fresh cut apples covered and uncovered with an edible film, through conventional techniques and through biospeckle which is an alternative method of quality evaluation. That analysis was correlated to methods, such as Hunter L＊, a＊ and b＊ parameters. Total soluble solids （TSS）, total titratable acidity （TTA）, respiration rate and pH, as well as the biospeckle optical technique, were measured through the calculation of the moment of inertia （MI）. Apples were sorted into three sets： samples with sodium alginate edible film, samples with pectin edible film and control samples with no film. In optical tests, a diode laser with a wavelength of 632 nm, a digital camcorder, a computer with image processing and statistical software were used. Results showed that both edible films （alginate and pectin） presented lower MI values, indicating the decrease of the biological activity. The conservation of the products observed through the reduction of biological activity promoted by the films keeps the apple quality for a longer period of time. The biospeckle technique can be related to the intensity of the biological activity of the vegetable tissue.

Apple Peel Biochemical Changes after Foliar Application of Combined Boron and Calcium I. Phenolics and Physico-Chemical Attributes

Post-full bloom foliar applications of boron in combination with calcium (B+Ca) suppress fruit sunburn-browning incidence in apples (Malus domestica). However, the mode-of-action is not yet explained and hence, protocols to exploit this seemingly cost-effective peel physiology augmenting approach compared to usual methods (shade-netting, overhead cooling and kaolin application which attenuate excess fruit heat-load), cannot be fully developed or promoted justifiably among growers. Apple fruit sunburn-browning disorders are rampant worldwide, partly because of climate change as well as high cost and inefficacy of the established methods. However, knowledge of B+Ca effect on apple peel physiology may unravel the mode-of-action, paving the way for commercialization of this novel approach. In this study, B+Ca effect on apple peel phenolics and selected fruit physico-chemical attributes was investigated, using studies conducted at two farms for two seasons in Western Cape, South Africa. Four foliar treatments varying in B, Ca and inclusion of zinc (Zn), were applied on ‘Cripps Pink’, ‘Golden Delicious’ and ‘Granny Smith’ apples in 2014/15 (only ‘Cripps Pink’) and 2015/16 (all cultivars) in randomized complete block design experiments with five replications. Fruit peel samples for quantitative determination of total phenolics and total flavonoids analyses were collected at different fruit maturity stages. Significant (p < 0.05) interaction (treatments and fruit maturity stages) effect was observed for total phenolics (‘Golden Delicious’ and ‘Granny Smith’ only) and total flavonoids (all cultivars). Physico-chemical attributes (fruit diameter, size and total soluble solids) were only evaluated in ‘Golden Delicious’ and ‘Granny Smith’, and no significant differences among treatments occurred. Since no clear treatment differences in apple peel phenolic patterns were observed, other appropriate biochemical aspects like photosynthetic pigments should be investigated among such foliar B+Ca treatments.

Gibberellic Acid₄₊₇and Benzyladenine, Cambium Disconnection, Nitrogen, and Tip Removal Influence on Branch Induction in Newly Planted Poorly Feathered “Fuji” Apple Trees

The use of well-feathered nursery trees on dwarfing rootstocks is crucial for establishing high-density apple orchards to ensure early production. Training trees to develop a tall spindle canopy architecture has gained popularity in high-density orchards during the past decade. However, commercially produced nursery trees often lack feathers or are unevenly branched, making initial training decisions difficult and delaying precocious fruiting. In this project, we studied the vegetative meristem activation response to partial scoring or partial girdling of the bark cambium above the bud, with and without application of 500 ppm Promalin (gibberellin4+7 + benzyladenine), tip removal of the tree leader at the silver tip stage on April 23, 2019, Promalin spray at 500 ppm at post-bloom stage on May 7, 2019, and nitrogen (N) as UAN-32 (32% N) application at five levels (60, 80, 100, 120, or 140 g actual N/tree) on June 20, 2019, in newly planted un-feathered or unevenly branched “Aztec Fuji” trees on Budagovsky 9 (Bud 9) in southwest Idaho, USA. Grower’s Short Cut trees received a heading cut to the leader at 60 cm above the ground and resulted in the emergence of 5 - 6 strong branches near the heading cut. These trees had larger trunk cross-sectional areas than scored or girdled trees. Scoring or girdling, with or without Promalin, significantly improved branching by increasing the number of branches and bourse shoots. In many cases, the effects of partial scoring, with or without Promalin, were similar to those of bark girdling which is a more risky and time-consuming process. Branches induced by scoring and girdling had sharper crotch angles relative to the vertical leader. Spraying Promalin during the post-bloom stage at 500 ppm was not as effective as scoring or girdling to initiate branches. Additional N rates or removal of the leader tip did not significantly impact branch induction.

Entire Whitening of Apple Trees to Increase Chill Units in Regions of Warm Temperatures during the Fall-Winter Seasons

Different studies have shown that global warming and climate change have increased the planet’s temperature in different locations. For the apple-growing farmers, this may have a negative impact on the accumulations of chill units when the air temperature during the fall-winter season increases. When the entire trees are covered with a reflective material, the wood temperature may decrease. Therefore, the objective of this study was to evaluate the effect of whitening (with calcium hydroxide) the entire apple trees (Malus domestica Borkh) after defoliation, on the branches and trunks’ internal temperature (under the bark), the accumulation of chill units (CU), its effects on fruit yield and quality and the relation with the use of thidiazuron (TDZ) (inducer of budbreak). The study was conducted during the fall-winter seasons of 2019-2020 and 2020-2021. The results of this study showed that at the hours of the highest incidence of solar radiation, the internal temperature of the whitened trunks and leaves decreases up to 9&deg;C and 6&deg;C respectively. The accumulated CU during the time of the study, of the whitened branches were up to 81% higher than the ones recorded on the branches with no whitening;while the CU was lost at the hours of highest solar radiation (due to a high temperature) were up to 37.2% smaller. Entire tree whitening increased up to 26% of the yield per tree compared to the application of TDZ. No statistical difference in fruit quality was observed between whitened trees and those with no whitening but with the application of thidiazuron.

Apple Peel Biochemical Changes after Foliar Application of Combined Boron and Calcium II. Photosynthetic Pigments, Total Peroxides and Photochemical Efficiency

Understanding of the physiological effect of post-full-bloom foliar boron combined with calcium (B+Ca) on apple (Malus domestica) peel tissues is envisaged to give way to the unknown mode-of-action by which these mineral regimens suppress fruit sunburn-browning incidence in orchards. Promotion of this mineral approach among growers, as a certainly cheaper alternative to mitigate fruit sunburn-browning incidence in apple orchards necessitates clear elucidation of its mode-of-action. This study investigated peel photosynthetic pigments and total peroxides (as a measure of oxidative stress) in three apple cultivars, ‘Cripps Pink’, ‘Golden Delicious’ and ‘Granny Smith’ which were treated with four B+Ca treatments varying in levels of B and Ca as well as inclusion of zinc (Zn) in one treatment. Randomized complete block design experiments with five replications were conducted at commercial farms in Western Cape, South Africa. Significant (p < 0.05) treatment effect for major pigment aspects and total peroxides occurred in all cultivars, but with strong influence of cultivar and fruit age. For instance, effect of varying B, Ca and possible B+Ca duet-effect on photosynthetic pigments occurred in ‘Cripps Pink’, whereas the Zn-treatment was mainly responsible for significant treatment effects in both ‘Golden Delicious’ and ‘Granny Smith’ apples. Significant treatment effect for total peroxides occurred in ‘Cripps Pink’ and ‘Granny Smith’, yet significant interaction effect occurred with ‘Golden Delicious’, however, these significant results did not yield meaningful peel oxidative stress differences among the treatments. Foliar treatment differences in photochemical efficiency (Fv/Fm) were not significant. The study concludes with firm evidence that foliar B+Ca treatment composition has a significant effect on apple peel photosynthetic pigments depending on cultivar, and Zn is not desirable in the formulation of these treatments.

茉莉酸甲酯对平邑甜茶光合、根构型及氮吸收的影响

茉莉酸甲酯能够明显影响果树的生长发育。为探索茉莉酸甲酯(MeJA)在苹果树生长发育中的作用,以苹果砧木平邑甜茶幼苗为试材,采用水培法开展叶面喷施茉莉酸甲酯对平邑甜茶光合、根系构型及氮素吸收的影响研究。结果显示,喷施茉莉酸甲酯能促进平邑甜茶植株生长、改善根构型及增强根活力、提高叶片叶绿素含量与净光合速率,影响根系对氮素等养分的吸收利用。中等浓度(2.5μmol·L^(-1))喷施效果最显著,而喷施高浓度(250μmol·L^(-1))的茉莉酸甲酯对植株生长、光合作用等有一定抑制作用。