ADAPTABILITY OF INTRODUCED HONEYSUCKLE VARIETIES IN THE PRE-URALS OF BASHKORTOSTAN

The article presents an assessment of the adaptability of introduced varieties of honeysuckle to the conditions of the Pre-Urals of Bashkortostan. The research was carried out at the primary variety study site of the Kushnarenkovsky breeding center of the BNIISKH UFIC RAS. Landing scheme 3.0´1.0 m. 7 varieties were selected as objects: varieties of selection of M.A. Lisavenko Research Institute of Horticulture - Zoluska, Galochka, Berel; varieties of YUUNIIPK - Chelyabinka, Chernichka; variety of Bakcharskaya experimental horticulture station - Bakcharskaya. As a control, the variety of the M. A. Lisavenko NIISS - Goluboe vereteno - was taken. The studies were conducted from 2016 to 2020. in accordance with the "Program and methodology of variety study of fruit, berry and nut crops". During the study, it was found out that all the studied varieties showed good winter hardiness. In 2017, damage to the apical buds of the winter desiccation type was observed in the varieties Chelyabinka and Zolushka by 23-25%. Dry conditions had a negative impact on productivity, leading to shedding of the ovary, a decrease in the weight of the fruit. The studied varieties differed among themselves in the degree of shedding. The control variety Goluboe vereteno is classified as highly crumbling, the weakly crumbling variety is Zolushka Chelyabinka, Bakcharskaya and the non - crumbling variety is Galochka, Chernichka and Berel. In the varieties Bakcharskaya, Berel and Goluboe vereteno, the extension of terminal buds was noted in the years of research. By weight of one berry, the following varieties were distinguished: Bakcharskaya (0.72 g), Galochka (0.75 g), Chernichka (0.81 g). The Chernichka (2.8 kg per bush) and Galochka (3.1 kg per bush) varieties were distinguished by high yield, on average, for 5 years. In general, the introduced varieties of honeysuckle show high adaptability in the natural and climatic conditions of the Pre-Urals of Bashkortostan.

Beilschmiedia danhkyii (Lauraceae), a new species from Vu Quang National Park, Vietnam

The new species Beilschmiedia danhkyii (Lauraceae) is described from Ha Tinh Province, Central Highland of Vietnam. Beilschmiedia danhkyii is characterized by ferruginous hairy terminal buds, branchlets and abaxial surfaces of lamina, subopposite leaves, adaxially impressed midrib and secondary veins, short inflorescence 2–3(–5) cm long, and large ellipsoid fruits 5–8 cm long, by which combination it is cleary distinguished from the other species of Beilschmiedia in the region. Taxonomic description, a table comparing morphological characters of the allied species, and color photo-plate are provided.

Locally adapted oak populations along an elevation gradient display different molecular strategies to regulate bud phenology.

Research conducted: With the ongoing global warming, there are serious concerns about the persistence of locally adapted populations. Indeed, with the raising of temperature, the phenological cycle of tree species may be strongly affected since higher winter temperatures may have a negative impact on endodormancy release if chilling requirements are not fulfilled during winter and late frost in spring may expose trees if buds flush too early. Thus, Environmental gradients (showing continuous variations of environmental conditions) constitute a design of choice to analyze the effect of winter dormancy in locally adapted population. Methods: In the present study, we used an elevation gradient in the Pyrenees to explore the gene expression network involved in dormancy regulation in natural populations of sessile oak locally adapted to temperature. Terminal buds were harvested during dormancy induction and release at different elevations. Then, gene expression was quantified using RNAseq and we used a likelihood ratio test to identify genes displaying significant dormancy, elevation or dormancy-by-elevation interaction effects. Key results: Our results highlight molecular processes in locally adapted populations along this elevation cline, and made it possible to identify key dormancy-by-elevation responsive genes revealing that locally adapted populations have evolved distinct molecular strategies to adapt their bud phenology in response to environmental variation (i.e. temperature).

Control of axillary bud growth in tobacco through toxin gene expression system

The control of axillary bud development after removing the terminal buds (topping) of plants is a research hotspot, and the control of gene expression, like switching on and off, allows us to further study biological traits of interest, such as plant branching and fertility. In this study, a toxin gene control system for plants based on dexamethasone (DEX) induction was constructed, and the positive transgenic tobacco exhibited growth retardation in the application area (axillary bud). The expression level of the lethal Diphtheria toxin A (DTA) gene under different DEX concentrations at different application days was analyzed. The highest expression levels appeared at 5 days after the leaf injection of DEX. The DTA transcripts were induced by 5 µM DEX and peaked in response to 50 µM DEX at 5 days after leaf injection. Here, a chemical induction system, combined with a toxin gene, were used to successfully control the growth of tobacco axillary buds after topping. The DTA expression system under DEX induction was sensitive and efficient, therefore, can be used to control axillary bud growth and development in tobacco.

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.

Seedling size and nutrient availability in the fall determine nitrogen resorption and storage compound allocation in Quercus variabilis

Aims Soil fertility and resorption of leaf compounds in the fall can influence resource buildup in plants. However, whether intraspecific differences in seedling size can affect nutrient reserve buildup is unknown. This study examined the effects of seedling size and fall fertilization on the uptake and resorption of nitrogen (N), as well as the allocation of non-structural carbohydrates (NSC) and N in cultivated Quercus variabilis Blume. Methods After the formation of terminal buds (T1), seedlings were stratified into small (shoot height < 30 cm) and large seedlings. During the hardening period, seedlings were treated with three different rates of 15N-enriched fertilizer (0, 12, or 24 mg N seedling− 1) and monitored until leaf fall (T2). Results Small seedlings had lower N resorption efficiency and resorbed proportionally less N than large seedlings. Fall fertilization notably improved N and NSC reserves, without reducing N resorption efficiency. Large seedlings allocated proportionally less N to leaves than small seedlings although both sizes seedlings absorbed similar amounts of N from fall fertilization. The priority perennial organ for NSC allocation was roots, while N allocation was dependent on the phenological growth stage of the seedling. Roots were prioritized during the rapid growth phase, while stems were prioritized during the hardening period. Conclusions Under same fertilizer regime during the growth phase, large seedlings tends to have lower N concentration and have higher resorption efficiency compare to small seedlings, fall fertilization can increase N storage in large seedlings and NSC levels in both seedling sizes, without affecting growth.

Dynamic Changes in Endogenous Hormones in Terminal Buds from Different Crown Positions in Sequoia sempervirens (Lamb.) Endl

Endogenous hormones can improve plant resistance and regulate growth and development. To obtain the basis of chemical control technology for improving Sequoia sempervirens resistance in Xuzhou, China, the current study probed the dynamic changes of endogenous hormones in terminal buds from different crown positions in S. sempervirens. Enzyme-linked immunosorbent assay (ELISA) was used to measure changes in the contents of endogenous hormones in terminal buds from the upper, middle, and lower lateral branches. The results were as follows: Indole acetic acid (IAA) in all terminal positions had a similar change trend of “rise–drop–rise.” Gibberellic acid (GA) in the upper and middle terminal buds showed similar trends of “drop–rise,” but GA in the lower lateral branches presented a “rise–drop” trend. Zeatin–riboside (ZR) in all terminal positions had similar change trends of “drop–rise.” Abscisic acid (ABA) in all terminal positions had similar change trends of “drop–rise–drop.” the trend of (IAA + GA + ZR)/ABA in all terminal positions was the same as that of IAA. Our results confirmed that, in autumn, the high content and ratio of stimulatory endogenous hormones in the terminal bud of S. sempervirens induced the terminal bud cells to continue to divide and grow, and the new branches could not be fully lignified and deeply dormant before the onset of low temperatures in winter, which led to a decrease in cold resistance and even the death of the terminal buds.

RNAi-mediated repression of dormancy-related genes results in evergrowing apple trees

DORMANCY ASSOCIATED MADS-box (DAM) and SHORT VEGETATIVE PHASE (SVP) genes have been implicated in the regulation of winter dormancy in perennials. Ectopic expression of apple (Malus ×domestica ‘Royal Gala’) DAM and SVP genes delays budbreak and constrains lateral shoot outgrowth. In this study, we used RNAi interference (RNAi) to simultaneously target all apple DAM and SVP genes to study their role and mode of action in the regulation of bud dormancy, budbreak and flowering. A synthetic construct carrying a hairpin fragment assembled from sequences specific to coding regions of three DAM and two SVP genes was used to generate transgenic lines. Reduced expression of DAM/SVP genes resulted in delayed leaf senescence and abscission in autumn, failure to enter bud dormancy in winter, and continual growth of new leaves regardless of the season for over 3 years. Precocious flowering but normal flower morphology, fertility and fruit development were observed. The non-dormant phenotype was associated with modified phytohormone composition. The content of gibberellins (GAs) and jasmonates (JAs) was significantly increased in terminal buds of RNAi lines compared to wildtype plants, accompanied by elevated expression of the key GA biosynthesis pathway gene GIBBERELLIN 20 OXIDASE-2 (MdGA20ox-2) along with the FLOWERING LOCUS T gene MdFT2. The key mediator of plasmodesmatal closure, MdCALLOSE SYNTHASE 1 (MdCALS1) was repressed in RNAi lines. This study provides functional evidence for the role of DAM/SVP genes in vegetative phenology of apple, and paves the way for production of low-chill varieties suitable for growth in warming climates.

Spring Freeze Damage of Pecan Bloom: A Review

Pecan is native to the United States. The US is the world’s largest pecan producer with an average yearly production of 250 to 300 million pounds; 80 percent of the world’s supply. Georgia, New Mexico, Texas, Arizona, Oklahoma, California, Louisiana, and Florida are the major US pecan producing states. Pecan trees frequently suffer from spring freeze at bud break and bloom as the buds are quite sensitive to freeze damage. This leads to poor flower and nut production. This review focuses on the impact of spring freeze during bud differentiation and flower development. Spring freeze kills the primary terminal buds, the pecan tree has a second chance for growth and flowering through secondary buds. Unfortunately, secondary buds have less bloom potential than primary buds and nut yield is reduced. Spring freeze damage depends on severity of the freeze, bud growth stage, cultivar type and tree age, tree height and tree vigor. This review discusses the impact of temperature on structure and function of male and female reproductive organs. It also summarizes carbohydrate relations as another factor that may play an important role in spring growth and transition of primary and secondary buds to flowers.

Variation of Endogenous Hormones during Flower and Leaf Buds Development in ‘Tianhong 2’ Apple

Hormones have an important role in apple flower bud differentiation; therefore, it is necessary to systematically explore the dynamic changes of endogenous hormones during flower and leaf bud development to elucidate the potential hormone regulation mechanism. In this study, we first observed the buds of ‘Tianhong 2’ apple during their differentiation stage using an anatomical method and divided them into physiologically differentiated stages of spur terminal buds, flower buds, and leaf buds. Then, we determined the contents of zeatin riboside (ZR), abscisic acid (ABA), auxin (IAA), and gibberellin (GA3) in these various types of buds using an enzyme-linked immunosorbent assay. The results showed that the content of ZR and the ratio of ZR to IAA in spur terminal buds decreased significantly during physiological differentiation. The contents of ZR, IAA, and GA3 in leaf buds culminated at the initial differentiation stage. The content of ZR in flower buds was significantly higher than that in leaf buds after formation of the inflorescence primordium and sepal primordium. Before the appearance of stamen primordium, the content of GA3 in flower buds was remarkably lower than that in leaf buds. The ratios of ABA/IAA and ZR/IAA in flower buds were significantly higher than those in leaf buds before the appearance of flower organ primordium. Moreover, ABA content, ABA/ZR, and ABA/GA3 in flower buds were higher than those in leaf buds throughout the whole flower bud morphological differentiation process. Therefore, the reduced ZR content was beneficial to floral induction. The low content of GA3, and high ratios of ABA/IAA and ZR/IAA were conducive to early morphological differentiation. In addition, high ratios of ABA/GA3 and ABA/ZR were beneficial to the morphological differentiation of flower buds. Moreover, the high ABA content was beneficial to floral induction and morphological differentiation of flower buds. Our results shed light on the mechanisms of hormonal regulation of apple flower bud differentiation and could potentially strengthen the theoretical basis for artificial regulation of apple flower bud development using exogenous plant hormones.