Shoot Survival Research Articles

Intraspecific variation influences performance of moss transplants along microclimate gradients.

Identifying the environmental drivers of population dynamics is crucial to predict changes in species abundances and distributions under climate change. Populations of the same species might differ in their responses as a result of intraspecific variation. Yet the importance of such differences remains largely unexplored. We examined the responses of latitudinally distant populations of the forest moss Hylocomiastrum umbratum along microclimate gradients in Sweden. We transplanted moss mats from southern and northern populations to 30 sites with contrasting microclimates (i.e., replicated field common gardens) within a forest landscape, and recorded growth and survival of individual shoots over 3 yr. To evaluate the importance of intraspecific variation in responses to environmental factors, we assessed effects of the interactions between population origin and microclimate drivers on growth and survival. Effects on overall performance of transplanted populations were estimated using the product of survival and growth. We found differences between southern and northern populations in the response to summer temperature and snowmelt date in one of three yearly transitions. In this year, southern populations performed better in warm, southern‐like conditions than in cold, northern‐like conditions; and the reverse pattern was true for northern populations. Survival of all populations decreased with evaporation, consistent with the high hydric demands and poikilohydric nature of mosses. Our results are consistent with population adaptation to local climate, and suggest that intraspecific variation among populations can have important effects on the response of species to microclimate drivers. These findings highlight the need to account for differential responses in predictions of species abundance and distribution under climate change.

Control of contaminants in the in vitro establishment of Guadua latifolia

ABSTRACT The Amazonian bamboo forests are located in an important region of high biodiversity in Brazil, Peru and Bolivia, forming the largest native bamboo forest reserve in the world. However, the bamboos from these forests have characteristics that hinder their propagation. This study aimed to evaluate the biocide action of a plant preservative mixture for controling contaminants, during the in vitro establishment of Guadua latifolia (Bonpl.) Kunth, a species native to the region. Nodal segments were cultured in a semi-solid medium containing Plant Preservative Mixture (PPMTM), at the concentrations of 0; 1; 2; and 3 mL L-1, and supplemented with 2 mg L-1 of 6-benzylaminopurine. The analyzed variables were number of shoots, percentage of bacterial and fungal contamination, and shoot survival. The treatments with the synthetic biocide were efficient in controlling the in vitro contamination caused by bacteria and fungi (Fusarium sp.), also presenting the highest survival rate of regenerated shoots. For the in vitro establishment of this native bamboo species, the use of 2 mL L-1 of PPMTM is recommended.

Rooting biostimulants for Coffea arabica L. cuttings

In the rooting process of Arabica coffee cuttings, plant hormones are used for inducing root formation. However, synthetic molecules cannot be used to form organic seedlings. The objective of this work was to evaluate the effect of nut grass extract and different concentrations and types of humic substances on Arabica coffee cuttings. Arabica coffee shoots were collected, and cuttings containing at least two buds were taken. The experiment had a three-factor design, 2 (without or with nut grass extract) x 2 (humic or fulvic acid) x 4 (0, 10, 25 and 50 mg.dm-³). The following vegetative data were evaluated: shoot height (cm), survival, remaining leaves, leaf pairs, vigor and number of shoots. The root length, area, volume, diameter, and fresh and dry mass were also evaluated. The enzyme activity of H+-ATPase, catalase, superoxide dismutase, alcohol dehydrogenase and esterase was also quantified. The results showed that the Arabica coffee cutting rooting rate was increased when treated with humic acid at a concentration of 10 mg.dm-³ in the presence of nut grass extract. The lowest oxidative stress was observed in the 10 mg.dm-³ humic and fulvic acid treatments, regardless of the use of the extract. Key words: Root system; IBA; humic acid; fulvic acid; shoots.

Taking advantage of seagrass recovery potential to develop novel and effective meadow rehabilitation methods.

Seagrasses are among the most threatened biomes worldwide. Until now, seagrass rehabilitation success has reached about 38% overall and more effective approaches to restoration are urgently needed. Here we report a novel method to rehabilitate Posidonia oceanica meadows based on observation of the species' natural recovery after disturbance. Posidonia oceanica rhizomes were transplanted on gabions filled with rocks of selected sizes in order to build a firm substrate with topographic complexity in the relevant scale range to propagules. Five techniques were tested, each involving a different anchoring device. The "slot" technique, which uses a wire-net pocket to retain the cuttings, was the most successful, with survival exceeding 85% after thirty months. Branching allowed final shoot survival to reach 422% of initial planting density. This study shows how an in-depth knowledge of species life history processes provides a suitable foundation for developing effective restoration methods that benefit from species recovery ability.

Efficacy of thermotherapy combined with chemotherapy and meristem tip culture in reducing Cassava brown streak virus in infected cassava

Thermotherapy, chemotherapy and meristem tip culture have been used either alone or in combination to eliminate viruses from plants. . The objective of this study was to determine the efficacy of combining thermotherapy with meristem tip culture and chemotherapy on the reduction of CBSV from infected cassava.Cassava Brown Streak Virus infected cuttings of Guzo variety collected from Coast region of Kenya, were established and maintained in a greenhouse at the Plant Quarantine Station, Kenya Plant Health Inspectorate Service (KEPHIS) in Muguga. Cassava leaves were sampled from eighteen plants and virus indexing done using RT-PCR with virus specific primers. Those confirmed to be positive for CBSV were used as initiation materials for the prospective test plants. From the initiated tissue culture materials, the 2nd subcultures were subjected to heat treatment at 38°C for 21 days. They were later subjected to ribavirin treatment at varying concentrations of (10mg/l, 20mg/l, and 30mgl) then left to establish for 14 days. Meristems of 1mm were excised from heat treated plantlets at 38°C for 21 days and cultured in vitro in modified Murasgige and skoog media. Nodal plantlets of 10mm not subjected to any treatment were used as controls. There was a significant difference (P<0.01) in the number of plants that survived among the treatments. Thermotherapy combined with chemotherapy resulted in complete mortality of plants due to the high stress levels from the high temperatures combined with the phytotoxic effect of the ribavirin. Thermotherapy followed by excision of meristem tips (1mm) resulted in 68.8% shoot survival with 84% being virus-free. Thermotherapy combined with meristem culture was successfully employed to produce CBSV-free cassava plants. Key words: Cassava Brown steak virus, Chemotherapy, meristem culture, Thermotherapy

Supervivencia y características de rebrotes en tocones de dos años de cultivos dendroenergéticos

Varias especies de los géneros Eucalyptus y Acacia son adecuadas para la producción de biomasa útil en la generación de energía. El objetivo del presente estudio fue evaluar la su-pervivencia y características del rebrote en tocones de cuatro especies dendroenergéticas en tres diferentes densidades poblacionales. Se utilizó un diseño de bloques completos al azar con tres repeticiones, en tres sitios (Parcelas Collipulli, La Aguada y Pilpilco Abajo) con características edafoclimáticas contrastantes. Se estudió Eucalyptus globulus, Eucalyptus denticulata, Eucalyptus nitens y Acacia dealbata en tres densidades de plantación (5 000 árboles/ha; 10 000 árboles/ha y 15 000 árboles/ha). Se evaluó el porcentaje de supervivencia y las características del rebrote por tocón. Las variables especie, densidad de plantación y sitio de siembra afectaron los parámetros analizados. La densidad de plantación afectó el diámetro y altura de los rebrotes dominantes de tipo proventicio en las cuatro especies estudiadas. La mayor tasa de supervivencia de tocones (97 %), la presentó Eucalyptus nitens en Pipilco Abajo, con 79 % de supervivencia de rebrotes a una densidad de 5 000 árboles/ha. Sin embargo, en densidades de 15 000 árboles/ha, la supervivencia de rebrote fue de 29 %. Acacia dealbata es una especie reconocida por su capacidad de colonización, sin embargo, en La Aguada, con densidades de siembra de 5 000 árboles/ha y 10 000 árboles/ha, mostró baja tasa de supervivencia de tocones (19 % y 18 %, respectivamente) y de rebrotes (57 % y 63 %, respectivamente). La especie Eucalyptus globulus mostró altas tasas de supervivencia de tocones y rebrotes en todos los sitios evaluados, por lo que puede ser considerada como una buena opción para optimizar el sistema de monte bajo.

Assessment of different temporary immersion systems in the micropropagation of anthurium (Anthurium andreanum).

Anthurium has been micropropagated mainly through conventional techniques in semisolid culture medium. However, this culture system involves constraints due to the low number of shoots produced and the high costs of the gelling agent and labor. Temporary immersion systems (TIS) are an alternative for increasing biological performance, reducing costs, and facilitating a semi-automated micropropagation process. The objective of this study was to compare the efficiency of different types of TIS during the in vitro propagation of anthurium. We used 2-cm-long nodal segments from in vitro plants. Explants were cultured in different TIS: temporary immersion bioreactors (TIB®), Ebb-and-Flow bioreactor, and recipient for automated temporary immersion (RITA®), with a 2-min immersion frequency at 12-h intervals. We used Murashige and Skoog (MS) medium supplemented with 3% (w/v) of sucrose and 8.88µM benzylaminopurine. After 60days of culture, we evaluated various physiological variables and the percent survival in the different TIS. The largest numbers of shoots per explant were observed in TIB® and Ebb-and-Flow, with 50.83 and 43.16 shoots per explant, respectively; the lowest number of shoots per explant was observed in RITA®, with 30.66. TIB® yielded the highest content of photosynthetic pigments (chlorophyll a, b, and total chlorophyll), stomatal index, and percentage of closed stomata relative to both Ebb-and-Flow and RITA®. The TIB® and RITA® systems showed a 99% shoot survival, while Ebb-and-Flow yielded 86% survival. In conclusion, TIS design and type affect a number of physiological processes and in vitro development, with TIB® as a feasible option for the commercial micropropagation of anthurium.

Gamma irradiation induced effects on in vitro shoot cultures and influence of monochromatic light regimes on irradiated shoot cultures of Dendrobium sonia orchid

The effects of gamma radiation and monochromatic lights on growth of in vitro shoot cultures of orchid, Dendrobium sonia, were investigated. The gamma irradiated shoot cultures grown under white, blue, yellow and red monochromatic lights exhibited differential growth pattern. Shoot cultures gamma irradiated at 15–45 Gy showed reduced shoot length, fresh weight and leaf area. The monochromatic light significantly influenced survival rate and growth of irradiated shoots. The yellow and red light treatments positively influenced survival of gamma irradiated shoots with significant increase in fresh weight, shoot length and chlorophyll content. Yellow light was found to be most effective as leaf area was increased across the radiation dose range (15–100 Gy) compared to red light. The results demonstrated that the method of post-irradiation exposure could be useful to improve growth of gamma irradiated in vitro shoots, and help to recover orchid mutants with novel modifications.

Tissue Culture of Regeneration Induced by Leaves of ‘Hongyang’

The test combined the concentration in 0.5mg⋅L−1, 1.0mg⋅L−1, 1.5mg⋅L−1 of 1-naphthaleneacetic acid (NAA) and a concentration of 2.0mg⋅L−1, 2.5mg⋅L−1, 3.0mg⋅L−1 of 6-benzylaminopurine (6-BA), from which we got a comprehensive evaluation of shoots survival ratio, growing point proliferated rate and shoots growth status together. From all the treatment we selected MS + 1.0mg⋅L−1 NAA + 3.0mg⋅L−1 6-BA for the optimum combination, for its live ratio of budding leaves on 92.59%, growing point proliferation rate on 629.60%. In this experiment, each treatment adventitious buds were over 300.00%, that all the treatments are able to use as the media formulations for proliferation of adventitious buds.

Grazing by wild giant pandas does not affect the regeneration of Arundinaria spanostachya

Arundinaria spanostachya is the main bamboo species on which giant pandas forage. Information on its regeneration capacity to meet the foraging demands of pandas is important to ensure the long-term survival of pandas. In 2014, 2 plot types (grazed versus control) were selected in the winter habitat used by one wild giant panda. Various morphological and regeneration characteristics of the bamboo were assessed in the respective plots during 2014 and 2015. The panda avoided feeding on bamboo with a basal diameter of < 6 mm, preferentially feeding on intermediate-sized bamboo. The density of new shoots and the recruitment rate of shoots were significantly higher in the grazed plots compared to the control plots. The annual recruitment rate of shoots was markedly higher than the annual mortality rate in the same plot type. After grazing, the basal diameter and height of new bamboo were similar between the 2 plots. In the grazed plots, the basal diameter of new bamboo was similar to that of the stumps. Innutrition and foraging by insects were the main factors influencing the survival of new shoots. Our results showed that grazing by giant pandas helped the clonal regeneration of A. spanostachya populations, with the basal diameter of new bamboo shoots meeting the foraging demand of pandas. However, information on the carrying capacity of A. spanostachya is necessary to ensure sufficient forage matter is available for reintroduced giant pandas. Furthermore, fertilization and insect control measures should be implemented during the shooting period to optimize A. spanostachya resources.

Combining Thermotherapy with Cryotherapy for Efficient Eradication of Apple stem grooving virus from Infected In-vitro-cultured Apple Shoots.

Apple stem grooving virus (ASGV), a difficult-to-eradicate virus from apple propagative materials, causes serious damage to apple production. The use of virus-free plants has been and is an effective strategy for control of plant viral diseases. This study aimed to eradicate ASGV from virus-infected in-vitro-cultured shoots of four apple cultivars and one rootstock by combining thermotherapy with cryotherapy. In vitro stock shoots infected with ASGV were thermo-treated using an alternating temperature of 36°C (day) and 32°C (night). Shoot tips were excised from the treated stock shoots and subjected to cryotherapy. Results showed that, although thermotherapy did not influence shoot survival rates, it reduced shoot growth and proliferation of in vitro shoots. Shoot regrowth rates decreased while virus eradication frequencies increased in cryo-treated shoot tips as time durations of thermotherapy increased from 0 to 6 weeks. Shoot regrowth and frequency of virus eradication were positively and negatively correlated, respectively, with the size of shoot tips. The protocol established here yielded shoot regrowth rates and virus eradication frequencies of 33 to 76% and 30 to 100%, respectively, in the four apple cultivars and one rootstock. Thermotherapy altered virus distribution patterns, subsequently resulting in production of a larger virus-free area in the thermo-treated shoot tips. Many cells in the top layers of apical dome and some cells in the youngest leaf primordia survived in cryo-treated shoot tips; these cells were most likely free of virus infection. Thus, plants regenerated from the procedure of combining thermotherapy with cryotherapy were free of ASGV, as judged by reverse-transcription polymerase chain reaction. To the best of our knowledge, this is the widest-spectrum technique reported thus far for the production of ASGV-free plants and provides a novel biotechnology for the production of virus-free plants in Malus spp.

Multiplicação in vitro e aclimatização de Melocactus sergipensis

Melocactus sergipensis is a newly discovered species, endemic to the state of Sergipe and critically endangered. The objective of this research was to establish a protocol for micropropagation and acclimation of M. sergipensis plants. The experimental setting was a completely randomized design, with four treatments, 10 replicates and in each experimental unit an explant was introduced. Explants were obtained from medial sections of the stem of approximately 5 mm. The nutrient medium was ½ salts of MS supplemented with 30 g L -1 of sucrose, gelled with 7 g L -1 of agar and with the following concentrations of phytoregulators: 6-benzylaminopurine (BAP) [0,0; 1,5; 3,0 and 6,0 mg L -1 ] and naphthalenoacetic acid (ANA) [0,0; 1,5; 3,0 and 6,0 mg L -1 ] and the BAP/ANA combinations [0,0; 1,0/0,5; 2,0/1,0 and 4,0/2,0 mg L -1 ]. The mean values of (shoots per explant, stem height and stem diameter) and percentage of calogenesis, rooting explants, survival of explants and shoots and weight of fresh matter were evaluated. Data were submitted to analysis of variance and means were compared by the Tukey test, 5% significance. There were no significant differences between treatments in relation to bud formation, callus, shoot and bud survival, stem height, stem diameter, and cracked weight. Nutritional supplementation with 1,0/0,5 BAP/ANA mg L -1 promoted a higher shoot formation. During the ex vitro phase, 70% of the normal shoots and 0,1% of the hyperhydric shoots survived.

Seagrass collapse due to synergistic stressors is not anticipated by phenological changes.

Seagrasses are globally declining and often their loss is due to synergies among stressors. We investigated the interactive effects of eutrophication and burial on the Mediterranean seagrass, Posidonia oceanica. A field experiment was conducted to estimate whether shoot survival depends on the interactive effects of three levels of intensity of both stressors and to identify early changes in plants (i.e., morphological, physiological and biochemical, and expression of stress-related genes) that may serve to detect signals of imminent shoot density collapse. Sediment burial and nutrient enrichment produced interactive effects on P. oceanica shoot survival, as high nutrient levels had the potential to accelerate the regression of the seagrass exposed to high burial (HB). After 11weeks, HB in combination with either high or medium nutrient enrichment caused a shoot loss of about 60%. Changes in morphology were poor predictors of the seagrass decline. Likewise, few biochemical variables were associated with P. oceanica survival (the phenolics, ORAC and leaf δ34S). In contrast, the expression of target genes had the highest correlation with plant survival: photosynthetic genes (ATPa, psbD and psbA) were up-regulated in response to high burial, while carbon metabolism genes (CA-chl, PGK and GADPH) were down-regulated. Therefore, die-offs due to high sedimentation rate in eutrophic areas can only be anticipated by altered expression of stress-related genes that may warn the imminent seagrass collapse. Management of local stressors, such as nutrient pollution, may enhance seagrass resilience in the face of the intensification of extreme climate events, such as floods.

Micropropagation of Epilobium canum garretti (Firechalice) by Axillary Shoot Culture

Epilobium canum subsp. garrettii (firechalice) is an herbaceous wildflower with landscape potential, but its seeds are difficult to germinate because of dormancy requirements. The objective of this study was to develop a complete micropropagation procedure for a selected accession of firechalice. Single-node stem explants from the plant were examined for their ability to establish on Murashige and Skoog (MS) medium or Woody Plant Medium (WPM). Shoot explants on MS medium supplemented with 4.4 μm benzyladenine (BA) produced more than double the number of axillary shoots compared to explants on WPM (12.6 vs. 4.9 shoots, P = 0.0001). Benzyladenine, kinetin (kin), 6-(γ,γ-dimethlyallylamino)purine (2iP), thidiazuron (TDZ), and meta-topolin (mT) at concentrations of 0, 1.1, 2.2, 4.4, or 8.8 μm were evaluated for shoot proliferation efficacy. Stem explants treated with 8.8 μm of BA or mT produced the most shoots, 11 or 15, respectively. Benzyladenine, 2iP, and kin failed to affect shoot height even at the highest concentrations used, but 4.4 or 8.8 μm TDZ reduced shoot height to less than half of the heights of control shoots (3.1 vs. 1.2 cm, P = 0.0001). Firechalice shoots formed three to four roots easily without auxin added to the medium, but four to six roots formed per shoot when using up to 9 μm of indole-3-butyric acid (IBA). In contrast, 9 μm naphthaleneacetic acid (NAA) prevented root formation. When using 0–9 μm IBA for rooting, 82.5% of the rooted shoots survived transplanting. Based on these results, optimum micropropagation of firechalice may be achieved with shoots established on MS medium plus 4.4 µm BA, a concentration of 4.4 or 8.8 μm BA or mT used for shoot proliferation, and use of up to 6 µm IBA during root induction should result in &gt;80% shoot survival after transplanting.

PROPAGATION OF A RARE ORNAMENTAL CLIMBER PLANT PORANA PANICULATA BY TISSUE CULTURE

This work was carried out in the Tissue Culture Laboratory, Horticulture Research Institute, Agricultural Research Center, Giza, Egypt during the period from 2015 to 2017, to investigate some factors affecting propagation of the rare ornamental climber Porana paniculata by tissue culture. Results could be briefed in the following: using clorox at 20% as a sterilant achieved the highest position in survival % and the lowest one concerning contamination %. The highest position was also occupied by clorox at 5% in relation to contamination %. Exposing explants to clorox for either 15 or 20 min gave rise to the highest survival %. Explants exposed to clorox at 20% for 15 min obtained the highest position in survival %, the pre-lowest rank in contamination % and the lowest one regarding mortality %. Using BAP at 0.60 ppm gave rise to the highest position in lateral buds survival %, regeneration capacity, culture efficiency, shoot number, shoot length and leaf number. Using 1/2 MS media induced the 1st position concerning lateral buds survival %, regeneration capacity, culture efficiency, shoot number, shoot length and leaf number. Using BAP at 0.60 ppm + 1/2 MS medium resulted in the highest records of lateral buds survival %, regeneration capacity, culture efficiency, shoot number, shoot length and leaf number. BAP at 0.40 ppm + 1/2 MS medium gave the 1st rank of shoot number. Using BAP at 1 ppm induced the 1st position regarding shoot survival %, shoot number, shoot length and leaf number. NAA at 0.1 ppm resulted in the 1st position regarding shoot survival %, shoot number, shoot length and leaf number. BAP at 1 ppm + NAA at 0.1 ppm recorded the 1st position concerning shoot survival %, shoot number, shoot length and leaf number.

Tree Physiology Optimization in Benchmark Function and Traveling Salesman Problem

Abstract Nature has the ability of sustainability and improvisation for better survival. This unique characteristic reflects a pattern of optimization that inspires the computational intelligence toward different scopes of optimization: a nondeterministic optimization approach or a nature-inspired metaheuristic algorithm. To date, there are many metaheuristic algorithms introduced with good promising results and also becoming a powerful method for solving numerous optimization problems. In this paper, a new metaheuristic algorithm inspired from a plant growth system is proposed, which is defined as tree physiology optimization (TPO). A plant growth consists of two main counterparts: plant shoots and roots. Shoots extend to find better sunlight for the photosynthesis process that converts light and water supplied from the roots into energy for plant growth; at the same time, roots elongate in the opposite way in search for water and nutrients for shoot survival. The collaboration from both systems ensures plant sustainability. This idea is transformed into an optimization algorithm: shoots with defined branches find the potential solution with the help of roots variable. The shoots-branches extension enhances the search diversity and the root system amplifying the search via evaluated fitness. To demonstrate its effectiveness, two different classes of problem are evaluated: (1) a continuous benchmark test function compared to particle swarm optimization (PSO) and genetic algorithm (GA) and (2) an NP-hard problem with the traveling salesman problem (TSP) compared to GA and nearest-neighbor (NN) algorithm. The simulation results show that TPO outperforms PSO and GA in all problem characteristics (flat surface and steep-drop with a combination of many local minima and plateau). In the TSP, TPO has a comparable result to GA.

Warming can enhance the detrimental effect of pathogens on a host plant, Miscanthus sinensis, in a cool-temperate montane grassland in Nagano, Japan

ABSTRACTThis study investigated the effects of two fungal pathogens, the smut fungus Sporisorium kusanoi and the discomycete Naemacyclus culmigenus, on the Japanese pampas grass Miscanthus sinensis, under experimental warming. In a cool-temperate grassland in a montane region, a field experiment was conducted with two treatments: 1) warming plots in open-top chambers (OTC); and 2) control plots with ambient temperature. Mean air temperature was 1.1°C higher in OTC than control. The fate, length, number of leaves, and aboveground biomass of uninfected and infected shoots of M. sinensis naturally established within the plots were recorded during the 2014 growing season. Disease symptoms emerged earlier in OTC. Infected shoots were shorter and had fewer leaves in OTC, whereas uninfected shoots were similar between OTC and control. Shoot biomass tended to be higher for uninfected shoots than infected shoots, but similar between OTC and control. Finally, shoot survival tended to be lower in OTC than control, as well as in infected than uninfected shoots. These results indicated that survival and growth of M. sinensis shoots were reduced following pathogen infection and that the detrimental effects of pathogens were more apparent under the warming condition.

Acrotomopus atropunctellus(Coleoptera: Curculionidae) Preference for Large Sugarcane Shoots Mitigates Damage to Sugarcane Crop

Summary The sugarcane weevil, Acrotomopus atropunctellus (Boheman) (Coleoptera: Curculionidae) is an increasingly important sugarcane pest in Argentina. Its emergence period overlaps with early stages of sugarcane phenology. This research assessed the preference of A. atropunctellus for shoot size and the effect of damage on shoot survival. Acrotomopus atropunctellus preferred to feed on large- and mediumsized shoots, regardless of sex. However, older plants were resistant to injury. Also, the number of punctures produced by females was 1.6 times greater than that produced by males. Avoiding late planting or harvest dates could be a useful tactic for mitigating A. atropunctellus incidence in sugarcane crops.

Quality of clonal plants of Piptocarpha angustifolia in different renewable substrates and seasons of the year

Abstract The objective of this work was to evaluate the effect of different compositions of renewable substrates and seasons of the year on the quality of Piptocarpha angustifolia clonal plants. The experiment was carried out in a completely randomized design in a 4x6 factorial arrangement (four seasons x six substrate compositions). The analyzed substrates were: S1, commercial substrate with pine bark and coconut fiber base (CF); S2, carbonized rice husk (CRH); S3, fibrous and grainy CF; S4, 50% CF and 50% CRH; S5, 30% CF and 70% CRH; and S6, 70% CF and 30% CRH. Minicuttings of 8±1 cm were planted in tubes of 110 cm3 and placed in a greenhouse, during the four seasons of the year. The evaluated variables were: survival and number of roots at 70 days; survival and emission of shoots at 100 days; rooting, shoot height, stem diameter, and their ratios; easiness of removal from tubes; aggregation to the substrate; and multiplication rate at 130 days. The highest CRH/CF ratio favored the development of better-quality plants, and S5 was the most adequate substrate. Spring is more favorable to the survival and quality of cuttings, and, together with summer, favors the highest multiplication rates. The S5 substrate has better physical and chemical quality and improves P. angustifolia clonal plants.

Determinants of spring barley yield in a high-yield potential environment

SUMMARYThe literature suggests that grain number largely determines and as such limits yield in barley. Many of the reported studies were conducted in relatively low-yielding environments and it is unclear if grain number is also a limiting factor in high-yield potential climates. Nor is it known with certainty what physiological or morphological traits must be targeted in order to increase grain number. A detailed programme of assessments was carried out on replicated field plots of a two-row spring barley variety (Hordeum vulgare L. cvar Quench) at three sites (Carlow, Wexford and Cork) in Ireland from 2011 to 2013. Plots were managed for high yield potential as per current best farm practice. Destructive sampling and in-field assessments were carried out at approximately weekly intervals from emergence onwards to gather growth, development and yield component data. Across nine site/seasons, grand means of 8·52 t/ha for yield, 18 419 for grain number/m2 and 46·41 mg for mean grain weight were achieved. Grain number/m2 accounted for most of the variation in yield and ear number/m2 accounted for most of the variation in grain number/m2. Early-season maximum shoot number/m2 had little influence on harvest ear number/m2. The period over which final ear number was determined was more flexible than the literature suggests, where the phases of tiller production and senescence varied considerably. Significant post-anthesis re-tillering occurred following the initial phase of shoot mortality at two out of nine site/seasons, but this appeared to contribute little to yield. Yield was positively associated with the proportion of shoots surviving from an early season maximum to a mid-season minimum (R2 = 0·62). Shoot size and weight at the beginning of stem extension had the largest influence on shoot survival, indicating that crop condition and hence growth and development pre-stem extension may be more important for shoot survival than growth and development during the stem extension period. Achieving high shoot numbers of adequate size and weight at the beginning of stem extension may be an appropriate target for establishing a high-yield potential crop.