Shoot Production Research Articles

EFFECT OF PRUNING HEIGHT ON THE PRODUCTION OF ORTOTROPIC BUDS OR BRANCHES IN VIVERO CONDITIONS

Introduction: reforestation constitutes an imperative need for current generations; this guarantees the sustainability of wood for different purposes, while promoting healthy conditions for the environment; The scientific community redouble efforts to investigate techniques that make reforestation increasingly feasible and viable. Objective: To determine the effect of pruning height according to the number of buds in the production of orthotropic shoots or branches under nursery conditions. Methodology: experimental, descriptive and longitudinal study in which young plants of Juglans neotrópica were subjected to clonal forestry techniques by means of training prunings in mother plants Different statistics were used to identify the statistical significance of the changes in the appearance of shoots according to the pruning height and number of buds; These include the use of Pearson's chi-square, the correlation for continuity, the likelihood ratio and the linear association for linear. Results: the plants submitted to the A2S2 combination were the ones that showed the best yield in relation to the appearance of shoots. The plants subjected to the A1S1 and A2S2 combinations were the ones with the greatest delay in the appearance of shoots. Conclusions: there is no significant relationship between the appearance of shoots and the height of pruning according to the number of buds; therefore, it can be determined that the buds will appear interchangeably whether the pruning is performed at three or five buds.

Estimating Fresh Weight of Individual Pea Shoots Using Measurable Morphological Characteristics

Nondestructive estimation of individual shoot fresh weight (FW) from its measurable morphological traits is useful for a wide variety of purposes in pea shoot production. To predict individual shoot FW, nine regression models in total were developed, including two power models using stem diameter (SMD) or stem length (SML) as a variable, and seven linear models using part or all the following variables: SMD, SML, leaflet length (LL), leaflet width (LW), stipule length (SEL), and stipule width (SEW). Among the nine models, the 6-variable linear equation had the highest coefficient of determination, R2 = 0.92, indicating it is most effective at explaining the variation in FW. The linear equations including only one variable, SMD or SML, were equally the least effective as nonlinear equations (i.e., power models). This finding suggests that there was a linear rather than nonlinear relationship between FW and the morphological variables. During stepwise regression, SEW and LW together were first removed from the 6-variable linear models without reducing the R2, and then SEL, SMD, SML were further removed one-by-one, which reduced the R2 from 0.92 to 0.90, 0.85, and 0.71, respectively. The result suggests that SMD, SML, SEL, and LL were the most important four predictor variables for multivariable linear regression models to estimate FW, an idea that was also supported by path analysis. For the four linear models with 1–4 predictor variables from stepwise regression, the prediction accuracy of FW was evaluated based on the agreement between the predicted and measured values using another independent dataset. The 4- and 3-variable linear models (i.e., FW = −1.437 + 0.276 SMD + 0.010 SML + 0.022 LL + 0.013 SEL and FW = −1.383 + 0.308 SMD + 0.011 SML + 0.030 LL, respectively) were selected for their more accurate prediction than 1- and 2-variable linear models and relatively simpler forms than a 6-variable linear model. Although the prediction accuracy can be potentially affected by air temperature, light conditions, and harvesting time, the multilinear regression model is an effective approach for estimating fresh weight of individual pea shoots using its measurable morphological traits.

Silencing the Oryza sativa plasma membrane H+-ATPase isoform OsA2 affects grain yield and shoot growth and decreases nitrogen concentration

The plasma membrane (PM) H+-ATPase (EC 3.6.1.3.) is a key component involved in nutrient uptake. There are 10 PM H+-ATPase isoforms in the rice genome (OsA1–OsA10), and OsA2 is highly responsive to nitrate (NO3−). We investigated the role that the OsA2 isoform plays in the total N and growth of rice (Oryza sativa). By the use of artificial microRNA, mutant osa2 rice lines presented ∼70 % downregulated levels of OsA2. Three osa2 lines and control plants (transformed with an empty IRS154 vector and named IRS) were cultivated in the greenhouse to evaluate grain and shoot production. For hydroponic experiments, the same lines were grown in Hoagland solution under two different NO3− levels for 30 days – 0.2 mM NO3−-N (low N) or 2.0 mM NO3−-N (sufficient N) – or were grown for three days without NO3− (starvation) after 27 days under 2.0 mM NO3−-N. In the greenhouse experiments, compared with the IRS plants, the osa2 lines had lower shoot fresh weights, grain yields and SPAD values. Moreover, compared with the IRS plants, the three osa2 lines grown hydroponically under low NO3− levels had lower N concentration and net flux of NO3−. PM H+-ATPase activity was lower in the osa2 mutants than in the IRS plants. The relatively low N concentration in the osa2 lines was not due to lower expression of OsNRT2.1, OsNRT2.2, or OsNAR2.1. These results indicate that the specific PM H+-ATPase isoform OsA2 affects the net flux of NO3−, N concentration, and grain yield.

Application of meta-Topolin for improving micropropagation of gooseberry (Ribes grossularia)

The aim of present study was to improve micropropagation of 14 gooseberry genotypes. The cytokinin meta-Topoline (mT) significantly increased the number of microshoots long enough for rooting and eliminated the incidence of necrosis and leaf yellowing. The mean shoot number on the medium containing 0.5 mg dm−3mT increased from 1.8 to 2.8 compared to medium with benzylaminopurine (BAP). In the second subculture on mT medium a mean shoot number was 3.8 and probability of production of shoots >1 cm increased from 0.18 to 0.44. In the same time shoot necrosis has fallen to zero in most cultivars. From the studied mT concentrations (0.25, 0.5 and 1.0 mg dm−3), the best effect for most genotypes was obtained at 0.5 mg dm−3. The auxin indole-3-acetic acid (IAA) or indole-3-butyric acid (IBA) added to the mT containing multiplication medium did not influence shoot number but in some genotypes generated tendency to necrosis. These results were reproduced during subsequent subcultures, thus enabling cyclic shoot multiplication.

Adventitious shoot-based propagation of Franklinia alatamaha for commercial horticulture and restoration

Franklinia is a monotypic genus of the family Theaceae that is now extinct in the wild. F. alatamaha Bartram ex Marshall has been maintained in cultivation for nearly 250-y because of the ornamental appeal of its flowers and foliage. The goal of this research was to develop an in vitro propagation system to increase the availability of this rare tree for commercial horticulture and restoration. Immature zygotic embryos were cultured on semi-solid Woody Plant Medium containing 34 different plant growth regulator treatments. Shoot organogenesis was induced from dark-grown explants with indole-3-butyric acid in combination with 6-benzylaminopurine. Shoot organogenesis was also obtained with thidiazuron, N-(2-Chloro-4-pyridyl)-N′-phenylurea, and indole-3-butyric acid in combination with meta-Topolin, although shoot development was abnormal. Adventitious buds were produced on the epidermal surfaces of immature zygotic embryos while exposed to the above plant growth regulator treatments. Once the adventitious buds elongated into shoots, these adventitious shoots were further multiplied by axillary shoot production. Elongated shoots from axillary shoot production were rooted on Woody Plant Medium supplemented with 0.25 g L−1 activated charcoal, but no plant growth regulators. The resulting plantlets were transferred to soil and acclimatized to the greenhouse and outdoor environments. Tissue culture-derived trees flowered within one and a half years in the greenhouse under an extended photoperiod.

Interactions among defoliation level, species, and soil richness determine foliage production during and after simulated spruce budworm attack

Defoliation level and site type are thought to influence tree response during spruce budworm (Choristoneura fumiferana (Clemens)) outbreaks. We determined the effects of four manual defoliation treatments (0%, 50%, 100%, and 100% + bud removal of current foliage) for 3 years on foliage production of balsam fir (Abies balsamea (L.) Mill.), black spruce (Picea mariana (Mill.) Britton, Sterns & Poggenb.), and white spruce (Picea glauca (Moench) Voss) trees on four site-quality classes. After 3 years of defoliation and 2 years of recovery, foliage biomass was reduced by 34%–98%. During defoliation, the number of shoots generally increased and shoot length of spruce generally decreased, especially on rich sites. During recovery, the number of shoots increased substantially, shoot length decreased, and bud destruction reduced the number of shoots by about 50% compared with that of trees that received the 100% defoliation treatment. Defoliation did not substantially affect needle length. Trees on rich sites had two- to fourfold greater foliage production than trees on poor sites. Effects of site and defoliation differed among species, but site quality, especially nutrition, played an important role in production of shoots and needles and the tree’s ability to withstand defoliation. Black spruce had more limited ability to recover foliage biomass, only producing more shoots, whereas balsam fir and white spruce had stronger ability to recover needle and shoot length, respectively.

Effect of Cytokinins on In Vitro Propagation of Ajuga xylorrhiza Kit Tan (Critically Endangered), Endemic to Turkey

Ajuga xylorrhiza Kit Tan is a rare endemic perennial species growing in the stony habitats in Southeastern Anatolia region, Turkey. An efficient and reproducible protocol has been developed for micropropagation of endangered Ajuga xylorrhiza. Shoots were cultured on Murashige and Skoog (MS) basal medium, supplemented with various concentrations of 6-benzyl amino purine (BAP), thidiazuron (TDZ), and kinetin (Kin). The optimal shoot formation was with the medium containing 0.125 mg L−1 BAP (7.91 shoots per explant), and 0.25 mg L−1 Kin (4.9 shoots per explant) was recorded. The best result in terms of shoot length (3.43 to 3.63 cm) was obtained from the Kin treatments. Kin parameters were more effective on shoot length and multiple shoot production than BAP and TDZ. For rooting, regenerated shoots were transferred to 1/4 strength MS medium containing two different concentrations of indole acetic acid (IAA) and α-naphthalenetic acid (NAA) at 0 (control), 0.5, or 1.0 mg L−1.The best results in terms of the number of roots per shoot were obtained from the medium supplemented with 0.5 mg L−1 IAA (3.10 roots per explant). Rooted plantlets were transferred to soil for acclimization with 100% success rate.

Responses to cryopreservation of recalcitrant seeds of Ekebergia capensis from different provenances

Recalcitrant seeds are shed at relatively high water contents and are metabolically active, initiating germination without exogenous provision of water. There is an urgency for these seeds to be conserved in light of the rapidly diminishing numbers of indigenous species and associated genetic diversity. This may be achieved by long term storage of whole seeds or seed germplasm. This study centred on the development of a cryopreservation protocol for embryonic axes (explants). Indicators of stress i.e. superoxide (·O2−), hydrogen peroxide (H2O2) and total aqueous antioxidants (TAA) levels were measured, as well as explant viability and shoot and root ultrastructure in response to exogenously applied cathodic water after each cryopreparative step.Explant viability gradually decreased after each cryopreparative step indicating the cumulative effect of the stresses imposed by cryopreservation. In conjunction with reduced viability, the levels of ·O2− and H2O2 increased gradually after each of these steps. Total aqueous antioxidant levels remained relatively unchanged throughout the cryopreservation process. The ROS levels in cathodic water treated explants were significantly lower compared with those that were not treated with cathodic water. A small number of explants from seeds obtained in Port Elizabeth (30%) survived after cryopreservation, while none of the explants from seeds obtained in St Lucia did.Root ultrastructure across explants from seeds of both provenances was well preserved after each cryopreparative step. Organelles were well developed and the ultrastructure was typical of metabolically active tissue. However, gradual ultrastructural deterioration was observed in the shoot meristem after each cryopreparative step. Typical of a stress response, increased vacuolation and a lack of visible organelles were noted. Root and shoot production (or lack thereof) was supported by ultrastructural observations.This study reports that the explants of PE origin were able to survive cryopreservation while those of St Lucia did not. The key findings of this study support the role of cathodic water in regulating ROS and indirectly preserving explant ultrastructure and survival, and its exogenous application during cryopreservation of recalcitrant seeded germplasm is recommended.

Micropropagation of Cleome dendroides (Cleomaceae), an endemic Brazilian species, as a source of glucosinolates

This is the first study related to micropropagation and phytochemical analyses of Cleome dendroides, an endemic species of the Brazilian Atlantic Forest, a biome affected by human activity. Among the classes of substances produced by the genus Cleome, the glucosinolates are used as chemotaxonomic markers. They have a wide structural diversity, which affords, for example, antineoplastic bioactivity. The micropropagation was established using explants from two sources: seedlings and in vitro plants. The morphogenic response was evaluated on Murashige-Skoog (MS) medium with different concentrations of benzyladenine (BA). Hypocotyl explants from seedlings and stem explants from in vitro plants showed higher capacity of shoot regeneration (56.3-100%). Shoot proliferation (75-100%) was maintained when hypocotyl explant-derived shoots and stem explant-derived shoots were subcultured three times a month. Hypocotyl explant-derived shoots maintained on MS + 2.0 mgL−1 BA induced the highest shoot production along the subcultures. Shoots were elongated and rooted on growth regulator-free MS medium. Plantlet establishment was successful in the hardening medium composed of Plantmax® substrate, reaching 85%survival. The phytochemical studies indicated two glucosinolate derivatives, highlighting the presence of 5,6-dimethyltetrahydro-1,3-oxazine-2-thione, identified for the first time in plants. This work demonstrates an efficient method for in-vitro production of C. dendroides plants, which can be used as a source of glucosinolates.

Rapid generation of transgenic and gene-edited Solanum nigrum plants using Agrobacterium-mediated transformation

In this study, genetic engineering methods, ranging from gene transformation to gene editing, were efficiently conducted on cotyledon explants in Solanum nigrum. Organogenic calli were observed on the explants following 10 days of growth on medium supplemented with 2 mg/L zeatin and 0.2 mg/L indole acetic acid (IAA), which we suggest to be an efficient shoot initiation medium (SM1). In vitro shoot production was enhanced in explants grown on media supplemented with 1 mg/L zeatin and 0.1 mg/L IAA, which we used as a proper shoot differentiation medium (SM2) in S. nigrum shoot regeneration. Direct infection of explants with Agrobacterium harboring CRISPR/Cas9 constructs can simplify the method of Agrobacterium-mediated T-DNA transformation by skipping the preincubation step. The method was applied to deliver transgenes for genome editing, such as CRISPR/Cas9 DNA. SnLazy1 locus, considered to be orthologs of tomato Lazy1, was edited using the CRISPR/Cas9 system in S. nigrum. Two independent deletion snlazy1-cr alleles were successively inherited and showed stem growth in a relatively downward direction. Our method offers rapid and simple procedure for gene transformation and genome editing that could be applicable for the enhancement of beneficial traits for precision plant breeding and engineering quantitative trait loci in S. nigrum.

بررسی تأثیر دو گونه قارچ میکوریزا-آربوسکولار در سطوح مختلف تنش رطوبتی بر برخی ویژگیهای رشدی ذرت

در شرایط تنش ، همزیستی گونه‌های قارچ میکوریزا-آربوسکولار با ریشه گیاه میزبان، تأثیر مستقیمی بر تحمل خشکی در گیاهان دارد. به‌منظور بررسی تأثیر دو گونه قارچ میکوریزا-آربوسکولار در سطوح مختلف تنش رطوبتی بر برخی ویژگی‌های رشدی ذرت، این آزمایش به‌صورت فاکتوریل با دو عامل در قالب طرح پایه کاملا تصادفی با پنج تکرار در شرایط گلخانه اجرا گردید. عامل اول مربوط به سطوح تنش رطوبتی شامل 60، 80 و 100% ظرفیت زراعی و عامل دوم مربوط به دو گونه قارچ میکوریزا شامل Glomus intraradices و Glomus mosseae و شاهد (عدم تلقیح) بودند. نتایج نشان داد که تنش رطوبتی موجب کاهش ارتفاع بوته و وزن خشک اندام هوایی به ترتیب به میزان13% و17% شد. تنش رطوبتی بر وزن خشک ریشه بی تاثیر بود ولی، قارچ‌های مایکوریزا وزن خشک ریشه را افزایش داده و تاثیر G. mosseae نسبت به گونه G. intraradices بیشتر بود. علیرغم افزایش شدت تنش رطوبتی، قارچ­های مایکوریزا شاخص کلروفیل SPAD را افزایش داد. بیشترین شاخص کلروفیل مربوط به تیمار تلقیح با قارچ G. mosseae در 0.6 ظرفیت زراعی معادل 37.02 بود. گیاه تلقیح شده با قارچ G. mosseae نسبت به G. intraradices کارایی بیشتری در حفظ رطوبت نسبی آب برگ در شرایط تنش رطوبتی داشت. بیشترین درصد کلونیزاسیون ریشه معادل 39.04 در تیمار تلقیح با قارچ mosseae G. در 60% رطوبت زراعی به دست آمد. به‌طورکلی، نتایج پیشنهاد می­کنند که در شرایط تنش رطوبتی، گونه G. mosseae قادر به برقراری ارتباط همزیستی مؤثرتری با ریشه گیاه ذرت تحت شرایط انجام این آزمایش بود.

Impact of Hormones on the Proliferation of Shoots and Initiation of Roots in Salvia santolinifolia (Boiss), A High Value Medicinal Herb

Salvia santolinifolia is a medicinal plant and an efficient in vitro conservation system is established. The influence of N6Benzylaminopurine (BAP), N6-(2-isopentyl)-adenine (2iP) and Kinetin at various concentrations were evaluated, single and in mixture with NAA (Naphthalene acetic acid) for the production of auxiliary shoots from nodal explants of S. santolinifolia. BAP at 3.0 mg/L in MS1 media produced maximum (11.66±3.38) number of shoots while elongated (5.37±1.45) shoots were produced in the MS2 medium in subcultures at 2.0 mg/L of 2iP. Least number of shoots were formed when auxin and cytokinin were used in combination. Length of culture, age was an important consideration for the initiation and development of roots. Rooting of shoot was attained with Indol-3-butyric acid (IBA) (3.0 mg/L) from shoots of 4th, 5th and 6th subculture while shoots taken from 1st, 2nd and 3rd subculture failed to form roots.

Somatic Embryogenesis and Plantlet Regeneration in the Carica papaya L. cv. Eksotika.

A highly efficient protocol for regeneration of Carica papaya L. cv. Eksotika somatic embryos from immature zygotic embryos was developed. This study was designed to overcome the obstacles in regeneration of somatic embryos from immature zygotic embryos of “Eksotika”, especially problems associated with formation of better root quality and callus formation at the base of somatic embryos. Somatic embryos were generated by incubation of immature zygotic embryos in half-strength salt Murashige and Skoog (MS) medium with full-strength vitamins supplemented with 7.5 mg L−1 2,4-D, 100 mg L−1 L-glutamine, 50 mg L−1 myo-inositol, 45 mg L−1 adenine sulphate, 0.33% gelrite, and 6% sucrose, followed by transfer to maturation medium consisting of ½ MS medium supplemented with 5 mg L−1 phloroglucinol, 100 mg L−1 L-glutamine, 100 mg L−1 myo-inositol, 68 mg L−1 adenine sulphate, 0.38% gelrite, and 3% sucrose. After that, well-formed somatic embryos were transferred to MS medium containing 3% sucrose and 0.8% agar for shoot production. The embryos were elongated in MS medium supplemented with 1 mg L−1 gibberellic acid, 0.5 mg L−1 indole-3-butyric acid, 100 mg L−1 myo-inositol, and 3.76 mg L−1 riboflavin. Root regeneration was achieved on MS medium containing 7.9 mg L−1 phloroglucinol and supported with vermiculite after 4 days of cultivation on ½ MS medium with 2 mg L−1 indole-3-butyric acid. After the rooting phase, in vitro plantlets were acclimatized in peat moss soil.

Nitrogen Fertigation in Lettuce Culture

Lettuce (Lactuca sativa L.) is the most consumed vegetable in the world and in Brazil, representing as an important dietary source of vitamins, fiber and minerals to population. The aim of this study was to evaluate the yield of lettuce against nitrogen doses applied via fertigation, as well as the quality of the administered fertilizer solution. The test was carried out in an agricultural area located in the Doutor Camargo municipality, Northwestern of Paraná State, Brazil. The experiment was designed in a completely randomized design with seven treatments: T1 control - 0 kg ha-1 urea (0 kg N ha-1); T2 - 25 kg ha-1 urea (11.25 kg N ha-1); T3 - 50 kg ha-1 urea (22.5 kg N ha-1); T4 - 75 kg ha-1 urea (33.75 kg N ha-1); T5 - application of 100 kg ha-1 urea (45 kg N ha-1); T6 - 125 kg ha-1 urea (56.25 kg N ha-1); T7 - 150 kg ha-1 urea (67.5 kg N ha-1). Each treatment had six repetitions. Seeds from Dora (American lettuce) and Vera (curly lettuce) varieties were used for seedling production. Nutrients were applied to the crop by fertigation at 15 and 30 days after transplanting the seedlings to the seedbeds. Fresh shoot mass (weight), stem diameter, root length and productivity were assessed. Results showed that nitrogen fertilization via fertigation significantly influenced the growth and yield variables of plants from both Dora and Vera varieties.

An Agrobacterium-mediated transformation via organogenesis regeneration of a facultative CAM plant, the common ice plant Mesembryanthemum crystallinum L

ABSTRACT The common ice plant, Mesembryanthemum crystallinum L. provides a useful model for the study of environmentally induced photosynthetic conversion and abiotic stresses tolerance. However, a procedure for the production of transgenic ice plant, which is essential for functional genomics, has not been fully established. Here we tested the factors on the transformation of cotyledonary nodes excised from the ice plant seedlings such as thidiazuron (TDZ), NaCl and phytosulfokine (PSK), a peptidyl plant growth factor using Agrobacterium tumefaciens strains EHA101 and EHA105 harboring binary vector plasmids pBI7EGFP and pCAMBIA1302, respectively. The established procedure is as follows: the explants (cotyledonary nodes) were co-cultivated with Agrobacterium for 3 days, and the explants were cultured in the medium with 0.5 mg l−1 kinetin and 100 mg l−1 carbenicillin for 72 h, and they were cultured in the medium with 0.5 mg l−1 kinetin and 100 nM PSKfor 4 weeks. Thidiazuron and NaCl enhanced the production of multiple adventitious shoot formation during regeneration but reduced the transformation efficiency due to the vitrification of adventitious shoots. PSK was effective in the production of healthy adventitious shoots. The transformation frequency at the stage of whole plants was 0.6% and 4.6% per inoculated cotyledonary nodes using the Agrobacterium strain EHA101 (pBI7EGFP) and EHA105 (pCAMBIA1302), respectively.

Micropropagation of Bambusa oldhamii Munro in heterotrophic, mixotrophic and photomixotrophic systems

Photomixotrophic micropropagation systems have been associated with improved development of several plant species. In this work, we established an efficient protocol for the in vitro micropropagation of Bambusa oldhamii Munro by studying the influence of the rainy and dry seasons on plant tissue contamination, the effects of the gaseous atmosphere inside the culture flasks, and the effects of radiation conditions on plant morphogenetic events. Explants were collected from March to December 2016. The conditions consisted of 100% blue (455 nm), 100% red (630 nm), 30% blue + 70% red, and 30% red + 70% blue LED light or fluorescent light only (as a control). For induction of axillary sprouting, the explants were inoculated in MS media + 2.27 µM thidiazuron or 3.40 µM paclobutrazol. The best growth responses were observed for material collected from June to July. There was an increase of 81.79% in the number of leaves under the 30% blue + 70% red LED treatment in comparison to the control. The facilitation of gas exchange resulted in improved shoot production, with an increase of 70.80% under 30% red + 70% blue LED light in comparison to that of treatments without gas exchange. The blue LED light had an important photomorphogenic effect on the development of bamboo explants into shoots, as shoot proliferation increased. The results obtained will aid in the development of protocols for the in vitro culture of other species of bamboo as well as for the establishment of an efficient protocol to address rooting for this and other bamboo species. Minimum temperature and compensated temperature resulted in significant impact on in vitro establishment. Blue + red combined with natural ventilation resulted in efficient shoot proliferation. Paclobutrazol increased the pigment content.

Interguild interactions between a non‐native phloem feeder and a native outbreaking defoliator

1. Competitive and synergistic interactions directly or indirectly drive community dynamics of herbivorous insects. Novel interactions between non‐native and native insects are unpredictable and not fully understood.2. We used manipulative experiments on mature red spruce trees to test interactions between a non‐native phloem feeding insect, the brown spruce longhorn beetle (BSLB), and an outbreaking native defoliator, the spruce budworm. We subjected treatment trees to defoliation by three densities of spruce budworm larvae. Treatment trees were: stressed by (i) girdling (to mimic beetle feeding) or (ii) girdling + BSLB before spruce budworm larvae were introduced on branches in sleeve cages. Budworm larvae then fed on foliage and developed to pupation. We assessed all branches for budworm performance, defoliation, shoot production and shoot growth.3. Shoot length did not differ in response to stress from girdling or BSLB infestation. Neither stress from girdling, nor interactions with BSLB feeding affected spruce budworm performance or defoliation. Intraspecific impacts on performance and defoliation in relation to budworm density were stronger than the effects of tree stress.4. Prior infestation of red spruce by BSLB in our experimental set‐up did not influence spruce budworm performance. BSLB is a successful invader that has blended into its novel ecological niche because of ecological and phylogenetic similarities with a native congener, Tetropium cinnamopterum.5. Outbreaks by BSLB will not likely impede or facilitate spruce budworm outbreaks if they co‐occur. It would be useful to evaluate the reverse scenario of BSLB success after defoliation stress by spruce budworm.

Effects of thinning intensity and growth parameters on Dendrocalamus brandisii (Munro) Kurz shoot production in Simao District, Yunnan Province, southwestern China

Bamboo shoots have been used by Chinese people as a popular and delicious dish up to 3000 years. Out of 534 bamboo species in China, about 50 species are used as source of edible shoot. However, little or almost no intensive management intervention has been applied for optimum shoot production of clump forming bamboo forest, especially for Dendrocalamus brandisii (Munro) Kurz. Therefore, the present study aimed to: (1) investigate the effects of thinning intensity on D. brandisii shoot production, (2) assess the effects of growth parameters on D. brandisii shoot production, and (3) develop a model to predict shoot production from a 5-year-old D. brandisii plantation. In February, using a randomized complete block design (RCBD) five thinning intensity treatments (1–0, 1-1, 2–1, 2-2 standing culm density (SCD) and control) were established in three blocks along an altitudinal gradient that covered an area of about 0.072 ha. Data collection (number of shoots and shoot yield) was conducted from mid-July to mid-October. A total of 130 edible shoots weighing 278.5 kg were harvested from 0.072 ha. This accounted for 2.89 harvested shoots clump−1 with 3.87 ton ha−1 shoot yield. On average, the largest shoot yield (2.74 kg or 5.84 ton ha−1) was harvested from a 2-2 standing culm density (SCD) (T4). The developed model illustrated that shoot yield was positively and significantly (p < 0.05) correlated with thinning intensity. The model further demonstrated that all culm DBH classes in T4 and/or T3 had the largest shoot yield compared to the control treatment (T5). Despite fewer numbers of shoots in T4 compared to T3, the larger shoot size in T4 made more attractive and promising for D. brandisii shoot production. Future studies should be considered on the combined effect of SCD, fertilizer regime and irrigation scheme for a better understanding about optimum shoot production.

TDZ-induced axillary shoot proliferation of Rhododendron mucronulatum Turcz and assessment of clonal fidelity using DNA-based markers and flow cytometry

In order to induce in vitro axillary shoot proliferation from single-node explants of Rhododendron mucronulatum Turcz., two techniques of thidiazuron (TDZ) application were tested: (i) two-step procedure including cultivation on Anderson medium (AM) supplemented with varying TDZ concentrations (0.1 μM; 0.25 μM; 0.5 μM; 1.0 μM; 2.5 μM) for 8 wk followed by cultivation on hormone-free medium (AM0) for 6 wk and (ii) 4-h liquid-pulse treatment with different TDZ concentrations (7.5 μM, 15.0 μM, or 30.0 μM) followed by cultivation on AM0 for 8 wk. The highest number of axillary shoots per explant was achieved with 0.1-μM TDZ after the two-step procedure. The best response in terms of percent regeneration (87%), shoot length (13 mm), absence of structure anomalies, and the shortest shoot production cycle (8 wk) was obtained with 30.0-μM TDZ liquid-pulse treatment for 4 h. The clonal fidelity of regenerated shoots was evaluated by random amplified polymorphic DNA (RAPD) and inter-simple sequence repeats (ISSR) markers and flow cytometry. Genetic similarity of all regenerants between themselves and with the mother seedlings was 99%. Flow cytometric analysis revealed that all samples studied were diploid. The nuclear DNA content of microshoots obtained under the TDZ treatments varied from 1.26 to 1.32 pg per 2C. There were no significant differences in DNA content among mother seedlings and in vitro developed shoots triggered by 0.1- and 2.5-μM TDZ nor by those triggered by the 30.0-μM TDZ pulse treatment.

Production of shoots from ‘Smooth Cayenne’ pineapple crowns with nitrogen fertilization

Abstract Pineapple fruit crowns are rarely used as planting material in Brazil. However, they can be used to produce plantlet in situations of scarcity of planting material of adequate quality. The aim of this work was to evaluate the production and nutritional status of early shoots of different sizes produced from ‘Smooth Cayenne’ pineapple crowns with nitrogen fertilization after the removal of its apical meristem. The experimental design adopted was that of randomized blocks in a 4x4 factorial scheme, with four nitrogen doses (5, 10, 15 and 20 g of urea per pot), four minimum shoot lengths at harvesting (10, 15, 20 and 25 cm), with four replicates. Under full sun cultivation conditions, crowns produced 18.11 and 6.83 shoots with 10 and 25 cm in length, respectively, up to 380 days after planting and removal of the apical meristem. Pineapple shoots harvested at 180 days presented better biometric quality and can be harvested up to 380 days after crown planting. Increasing urea doses reduce P, K and Ca levels in the dry mass of shoots.