Late Emergence and Rapid Growth Maximize the Plant Development of Miscanthus Clones

To develop the perennial grass Miscanthus x giganteus as a highly productive crop for biomass production, new varieties need to be bred, and more knowledge about its growth behaviour has to be collected. Our aim was to identify an efficient function for assessing and comparing emergence date and canopy height growth (rate, duration, and final maximal height) of 21?clones of Miscanthus in Northern France. Flow cytometry made it possible to classify the clones into three clusters corresponding to 2x, 3x, and 4x ploidy levels. Three functions, 3- and 4-parameter logistic functions and Gompertz function, were tested to best describe the dynamics of crop emergence and of plant growth. The best functions were used to estimate emergence dynamics (Gompertz function), and growth dynamics (4-parameter logistic). All these traits showed a significant year, clone, and corresponding interaction effects (but not for harvest date). Species and ploidy level explained the clone and clone × year interaction effects. M. x giganteus and M. floridulus clones were among the latest to emerge, and the tallest. M. sinensis clones showed the lowest height and growth rates. Higher final canopy height was correlated to late emergence and high growth rate. These findings could help early selection of interesting clones within M. sinensis populations, in order to breed new inter-species hybrids of giganteus type.     

Phenotypic Variation in Senescence in Miscanthus: Towards Optimising Biomass Quality and Quantity

Senescence impacts the harvestable biomass yield and quality in Miscanthus. Very early autumn senescence shortens the canopy duration reducing yield potential. When senescence is too late or slow, the crop does not ripen sufficiently before harvest, resulting in high moisture and nutrient offtakes that reduce biomass quality. In this study, variation in senescence was monitored over 3?years in a trial of 244 Miscanthus genotypes planted in four replicate blocks. The experiment comprised 199 genotypes of Miscanthus sinensis, 36 genotypes of Miscanthus sacchariflorus, and 9 genotypes of Miscanthus?×?giganteus. On average, M. sinensis genotypes remained greener for longer than M. sacchariflorus genotypes. There was a strong correlation between senescence and moisture content at harvest in 2007 and 2008 (R ²?=?0.59, R ²?=?0.57, respectively; n?=?244). The senescence rate of M.?×?giganteus, an interspecific hybrid between M. sinensis and M. sacchariflorus, was found to lie between the two parental species groups. Environmental signals likely to be involved in the timing and rate of senescence, such as variation in photoperiod and thermal time that occurred through the growing season were investigated. Interactions between individual environmental signals and senescence were difficult to separate. The majority of plants senesced consistently between replicate blocks, and rank order was mostly consistent across all years suggesting strong genotypic control of senescence. This study provides valuable information for the future optimisation of Miscanthus, and potentially other energy grasses, where new varieties are needed to maximise net energy yields and crop quality for different end uses in different global regions.     

Overwintering problems of newly established Miscanthus plantations can be overcome by identifying genotypes with improved rhizome cold tolerance

Miscanthus , a perennial rhizomatous C₄ grass, is a potential biomass crop in Europe, mainly because of its high yield potential and low demand for inputs. However, until recently only a single clone, M. × giganteus , was available for the extensive field trials performed across Europe and this showed poor overwintering in the first year after planting at some locations in Northern Europe. Therefore, field trials with five Miscanthus genotypes, including two acquisitions of Miscanthus × giganteus , one of M. sacchariflorus and two hybrids of M. sinensis were planted in early summer 1997 at four sites, in Sweden, Denmark, England and Germany. The field trials showed that better overwintering of newly established plants at a site was not apparently connected with size or early senescence. An artificial freezing test with rhizomes removed from the field in January 1998 showed that the lethal temperature at which 50% were killed (LT₅₀) for M. × giganteus and M. sacchariflorus genotypes was −3.4 °C. However, LT₅₀ in one of the M. sinensis hybrid genotypes tested was −6.5 °C and this genotype had the highest survival rates in the field in Sweden and Denmark. Although the carbohydrate content of rhizomes, osmotic potential of cell sap and mineral composition were not found to explain differences in frost tolerance adequately, moisture contents correlated with frost hardiness (LT₅₀) in most cases. The results obtained form a basis for identifying suitable Miscanthus genotypes for biomass production in the differing climatic regions of Europe.     

Investigating the Efficacy of Integrating Energy Crops into Non-Profitable Subfields in Iowa

Within-field spatial variability reduces growers’ return on investment and overall productivity while potentially increasing negative environmental impacts through increased soil erosion, nutrient runoff, and leaching. The hypothesis that integrating energy crops into non-profitable segments of agricultural fields could potentially increase grain yield and biomass feedstock production was tested in this study using a statewide analysis of predominantly corn- and soy-producing counties in Iowa. Basic and rigorous controls on permissible soil and soil-carbon losses were imposed on harvest of crop residues to enhance year-to-year sustainability of crop and residue production. Additional criteria limiting harvesting costs and focus on large-area subfields for biomass production were imposed to reduce the impacts of energy crop integration on grain production. Model simulations were conducted using 4 years (2013–2016) of soil, weather, crop yield, and management practice data on all counties in Iowa. Miscanthus (Miscanthus x giganteus), switchgrass (Panicum virgatum), and crop-residue-based bioenergy feedstock systems were evaluated as biomass. Average energy crop and plant residue harvesting efficiencies were estimated at 50 and 60%, respectively. Because of higher potential yields, average logistics costs for miscanthus-based biomass production were 15 and 23% lower than switchgrass-based and crop residue-based biomass productions, respectively, under basic sustainability controls, and 17 and 26% lower under rigorous sustainability controls. Subfield shape, size, area, and harvest equipment size were the dominant factors influencing harvesting cost and efficiency suggesting that in areas where subfields are predominantly profitable or harvesting efficiencies low, other options such as prairie strips, buffer zones around fields, and riparian areas should be investigated for more profitable biomass production and sustainable farming systems.     

Phenological responses of upland rice grown along an altitudinal gradient

High altitude upland rice (Oryza sativa L.) production systems are expected to benefit from climate change induced increase in temperatures. The potential yield of rice genotypes is governed by the thermal environment experienced during crop development phases when yield components are determined. Thus, knowledge on genotypic variability in phenotypic responses to variable temperature is required for assessing the adaptability of rice production to changing climate. Although, several crop models are available for this task, genotypic thermal constants used to simulate crop phenology vary strongly among the models and are under debate. Therefore, we conducted field trials with ten contrasting upland rice (O. sativa L.) genotypes on three locations along an altitudinal gradient with five monthly staggered sowing dates for two years in Madagascar with the aim to study phenological responses at different temperature regimes. We found that, crop duration is equally influenced by genotype selection, sowing date and year in the high altitude. In contrast, in mid altitudes genotype has no effect on crop duration. At low altitudes crop duration is more affected by sowing date. Grain yield is strongly affected by low temperatures at high altitudes and severly influenced by frequent tropical cyclones at low altitudes. In high altitude, genotype explained 68% of variation in spikelet sterility, whereas in mid and low altitudes environment explained more than 70% of the variation. The phenological responses determining crop duration and yield, the basic genotypic thermal constants, and the analyses of genotypic thermal responses with regard to spikelet sterility reported here, provide valuable information for the improvement of rice phenological models urgently needed to develop new genotypes and better adapted cropping calendars.     

More Productive Than Maize in the Midwest: How Does Miscanthus Do It?

In the first side-by-side large-scale trials of these two C₄ crops in the U.S. Corn Belt, Miscanthus (Miscanthus × giganteus) was 59% more productive than grain maize (Zea mays). Total productivity is the product of the total solar radiation incident per unit land area and the efficiencies of light interception (ε_i) and its conversion into aboveground biomass (ε_ca). Averaged over two growing seasons, ε_ca did not differ, but ε_i was 61% higher for Miscanthus, which developed a leaf canopy earlier and maintained it later. The diurnal course of photosynthesis was measured on sunlit and shaded leaves of each species on 26 dates. The daily integral of leaf-level photosynthetic CO₂ uptake differed slightly when integrated across two growing seasons but was up to 60% higher in maize in mid-summer. The average leaf area of Miscanthus was double that of maize, with the result that calculated canopy photosynthesis was 44% higher in Miscanthus, corresponding closely to the biomass differences. To determine the basis of differences in mid-season leaf photosynthesis, light and CO₂ responses were analyzed to determine in vivo biochemical limitations. Maize had a higher maximum velocity of phosphoenolpyruvate carboxylation, velocity of phosphoenolpyruvate regeneration, light saturated rate of photosynthesis, and higher maximum quantum efficiency of CO₂ assimilation. These biochemical differences, however, were more than offset by the larger leaf area and its longer duration in Miscanthus. The results indicate that the full potential of C₄ photosynthetic productivity is not achieved by modern temperate maize cultivars.     

Long-Term Miscanthus Yields Influenced by Location,Genotype, Row Distance,Fertilization and Harvest Season

Long-term yield studies in perennial crops like miscanthus are important to determine mean annual energy yield and the farmer’s economy. In two Danish field trials, annual yield of two miscanthus genotypes was followed over a 20-year period. The trials were established in 1993 on loamy sand in Foulum and on coarse sand in Jyndevad. Effects of genotype, row distance and fertilization were investigated. In both trials, yield development over time was characterized by an increase during the first years, optimum yields after 7–8 years and a decrease to a lower level which remained relatively constant from year 11 to 20. Spring harvest reduced the yield by 34–42 % compared to autumn harvest. In Foulum annual fertilization with 75 kg ha^?1 N increased the yield of the genotype Goliath (Miscanthus sinensis) by 26 %. Additional N fertilization only increased the yield of Goliath little, and the genotype Giganteus (Miscanthus?×?giganteus) did not respond to fertilization at all. The highest mean yield in Foulum for the period 1997–2012 was obtained with the shortest row distance (～18,000 rather than ～12,000 plants ha^?1) and harvested in late autumn, namely 13.1 and 12.0 Mg ha^?1 DM annually for Giganteus and Goliath, respectively. In Jyndevad, where only Goliath was studied, the highest yield during 1995–2001 was obtained by short row distance, autumn harvest and annual fertilization with 75 kg ha^?1 N, with yield increasing up to 116 % in response to fertilization. A mean yield of 14.4 Mg ha^?1 DM was achieved over the period 1995–2012.     

Shoot organogenesis in three Miscanthus species and evaluation for genetic uniformity using AFLP analysis

A simple, efficient protocol for direct in vitro shoot organogenesis and regeneration was established for three species of Miscanthus including two clones of Miscanthus x giganteus, one clone of M. sinensis and one clone of M. sacchariflorus. Shoots were induced from the axillary nodes of both M. x giganteus and M. sacchariflorus and from apical meristems of both M. sinensis and M. sacchariflorus. A tillering method was used to accelerate shoot proliferation. Shoots were rooted in a wet perlite substrate in pots in the greenhouse. Subsequently, rooted plants were transferred to the field. The genetic uniformity of regenerated plants was evaluated using amplified fragment length polymorphism analysis and compared to that of rhizome-propagated plants. A total of 33,443 fragments were generated, representing 869 markers. There were 21 fragments (0.06 % of the fragments) or 19 markers (2.19 % of the markers) that were polymorphic, and almost all of these were singletons. The three species showed similar polymorphisms. Genetic variability was also found in the rhizome-propagated plants, sometimes at a higher rate than in the in vitro culture, indicating that the genetic uniformity was not altered by the protocol. This protocol may help breeders produce new clones of Miscanthus in the future.     

A new genotype of Miscanthus sacchariflorus Geodae-Uksae 1, identified by growth characteristics and a specific SCAR marker

Miscanthus is referred to as an ideal lignocellulosic bioenergy crop, which can be used to generate heat, power, and fuel, as well as to reduce carbon dioxide emissions. The new Miscanthus sacchariflorus genotype named Geodae-Uksae 1 was recently collected from damp land in southern Korea. This study investigated the growth characteristics of Miscanthus genotypes, and developed a specific, sensitive, and reproducible sequence characterized amplified region (SCAR) marker to distinguish new M. sacchariflorus genotype Geodae-Uksae 1 from other native Miscanthus species in Korea. Growth characteristics such as stem length, stem diameter, and dry weight of Geodae-Uksae 1 were greater than those of normal M. sacchariflorus. The genotypes within Geodae-Uksae 1 were had the highest genetic similarity. A putative 1,800-bp polymorphic sequence specific to Geodae-Uksae 1 was identified with the random amplified polymorphic DNA (RAPD) N8018 primer. The sequence-characterized amplified region (SCAR) primers Geodae 1-F and Geodae 1-R were designed based on the unique RAPD amplicon. The SCAR primers produced a specific 1,799-bp amplicon in authentic Geodae-Uksae 1, whereas no amplification was observed in other Miscanthus species. The SCAR marker could contribute to identify Geodae-Uksae 1 among native Miscanthus species. The new Miscanthus genotype Geodae-Uksae 1 has great potential as an alternative lignocellulosic biomass feedstock for bioenergy productions.     

Can perennial dominant grass <Emphasis Type="Italic">Miscanthus sinensis</Emphasis> be nurse plant in recovery of degraded hilly land landscape in South China?

Perennial C₄ grasses, especially Miscanthus sinensis, are widely distributed in the degraded lands in South China. We transplanted native and exotic tree seedlings under the canopy of M. sinensis to assess the interaction (competition or facilitation) between dominant grass M. sinensis and tree seedlings. The results of growth, chlorophyll fluorescence, and ultrastructure showed that negative effects may be stronger in perennial dominant grass M. sinensis. Although M. sinensis buffered the air temperature, improved soil structure, and increased soil phosphorus content, these beneficial effects were outweighed by the detrimental effect, especially overshading. To ensure the establishment of target native species in M. sinensis communities in degraded lands of South China, restoration strategies should include removing aboveground vegetation, planting target species seedlings in openings to reduce the effects of canopy shading, and/or selecting competition-tolerant target species. Also, seedlings of exotic species used in restoration engineering cannot be directly planted under the canopy of M. sinensis.     

A Comparison of the Energy Yield at the End User for M. x giganteus Using Two Different Harvesting and Transport Systems

A comparison between two different harvest systems for Miscanthus x giganteus crop (direct cut/chip and mow/bale) in terms of the net energy delivered to an end user, and the various energy costs and energy yields associated with each system was conducted. Only minor differences in terms of energy consumption were observed between the two harvest systems when all phases of the harvesting chain had been taken into account. Chip harvesting consumed 0.11 GJ?t^?1 compared with 0.13 GJ?t^?1 for bale harvesting. Chip transportation was considerably more expensive than bale transportation for a set distance of 50 km (0.18 and 0.11 GJ?t^?1 for chip and bale, respectively). Despite this, higher overall net energy yield was achieved by direct cutting and chipping the material. This was due to the higher proportion of harvestable energy lost in the field as a result of the use of a mowing/baling system. The overall net energy delivered in terms of harvestable material by the direct cut and chip system was 12.45 GJ?t^–1 compared with 11.78 GJ?t^?1 by the mow and bale system, making direct cut the more efficient system even up to a transport distance of 400 km. A sensitivity analysis indicated that the choice of transport system becomes more important for energy efficiency as transport distance increases.     

Can multiple harvest of aboveground biomass enhance removal of trace elements in constructed wetlands receiving municipal sewage?

Constructed wetlands for wastewater treatment in the Czech Republic are commonly planted with reed canarygrass (Phalaris arundinacea). Phalaris is a fast-growing grass which may be cut several times during the growing season. During 2005, the experiments were carried out at horizontal sub-surface flow constructed wetland B?ehov to evaluate whether multiple harvest may increase the amount of 23 trace elements removable via mowing. The plants were cut in mid-June and re-harvested in mid-August. The single harvest was carried out at the end of July during the peak standing crop of this species. The biomass of Phalaris cut once and twice during the year was nearly identical but analyses of the biomass indicated that the amount (standing stock) of trace elements varied. For 13 elements (As, Ba, Co, Cr, Cu, Fe, Ga, Hg, Mn, Ni, Pb, Sb and U) the standing stock was higher for single harvest, indicating that these trace elements are transported to the aboveground biomass later in the growing season. Standing stock found in the biomass harvested at the peak standing crop as percentage of the cumulative standing stock from two harvests was highest for Hg (385%), Pb (249%) and U (244%). On the other hand, for 10 elements (Al, Cd, Li, Mo, Rb, Se, Sn, Sr, Tl and Zn) cumulative standing stock was higher than the standing stock for one harvest, indicating high accumulation during the early growth stages. For those elements, multiple harvest could be beneficial for element removal from wastewater.     

Early Clonal Survival and Growth of Poplars Grown on North Carolina Piedmont and Mountain Marginal Lands

The western half of North Carolina has abundant marginal pasturelands that vary greatly in altitude. Studies have demonstrated high Populus productivity on coastal plains and eastern Piedmont regions. Our objective was to identify best-performing Populus clones on marginal pasturelands representing upper Piedmont (Salisbury, 215 m above sea level, m.a.s.l.), northern Blue Ridge Mountains (Laurel Springs, 975 m.a.s.l.), and southern Blue Ridge Mountains (Mills River, 630 m.a.s.l.). At Salisbury, height and basal diameter (BD) were significantly related to clones (p?<?0.0001), and some clones were affected by clone-spacing interaction while spacing affected aboveground wood volume significantly (p?<?0.0001). At Mills River, clonal survival (p?<?0.0011), height, and volume (p?<?0.0051) varied with contrasting significance of some clonal differences between spacings. At Laurel Springs, survival varied among clones in 1 m?×?1 m spacing (p?=?0.003) but not 2 m?×?2 m spacing while heights and volumes differed in both spacings (p?<?0.0058). Clone 185 was consistently in the top 10 % for height, BD, and survival at all sites and spacings while other clones performed variably. Height-BD regressions were affected by clones, spacing, and sites. Volume had no clear correlations with precipitation, photosynthetically active radiation, temperature, and altitude across sites while height correlated with precipitation. Our results compared favorably with published results in other US regions, and show short rotation poplars have efficacy in Piedmont and mountain regions if the right clones in terms of growth/productivity, survival, and disease resistance are selected. Larger clonal performance variations are expected as competition increases, and highlight importance of experimentally determining suitable clones for specific sites.     

Resistance of Sugarcane Cultivars to Mahanarva fimbriolata (Stål) (Hemiptera: Cercopidae)

The spittlebug Mahanarva fimbriolata (Stål) (Hemiptera: Cercopidae) is one of the most important pests of the sugarcane crop in Brazil. Despite of its importance, there is currently a lack of information regarding sugarcane cultivars’ resistance to the spittlebug. Therefore, our objective was to evaluate the response of sugarcane genotypes to this species. Two experiments were carried out under laboratory conditions using a random block design with treatments in a factorial arrangement of 2?×?13 (experiment 1) and 2?×?12 (experiment 2), with six replicates. The first factor included two levels of infestation (infested and noninfested plants with spittlebugs), while the second consisted of the cultivars. Nymph survival varied from 47.9 to 84.5%, indicating that there are different levels of antibiosis to M. fimbriolata among the tested cultivars. The highest degree of antibiosis was found in cultivars IACSP96-7586 and IACSP96-2008, in which nymph survival was close to 48%. IACSP96-7586 also presented some degree of tolerance, but IACSP96-7569 and IACSP97-6682 stood out as the most tolerant cultivars to the pest, showing the lowest reduction in weight of aboveground biomass. On average, spittlebug infestations caused a significant reduction in relative leaf chlorophyll content and aboveground biomass weight.     

Cultivation of Miscanthus under West European conditions: Seasonal changes in dry matter production,nutrient uptake and remobilization

There is increasing interest in cultivation of Miscanthus as a source of renewable energy in Europe, but there is little information on its nutrient requirements. Our aim was to determine the nutrient requirement of an established Miscanthus crop through a detailed study of nutrient uptake and nutrient remobilization between plant parts during growth and senescence. Therefore dry matter of rhizomes and shoots as well as N, P, K and Mg concentration under three N fertilizer rates (0, 90, and 180 kg N ha-1) were measured in field trials in 1992/93 and at one rate of 100 kg N h-1 in 1994/95.Maximum aboveground biomass in an established Miscanthus crop ranged between 25-30 t dry matter ha-1 in the September of both trial years. Due to senescence and leaf fall there was a 30% loss in dry matter between September and harvest in March. N fertilization had no effect on crop yield at harvest. Concentrations of N, P, K and Mg in shoots were at a maximum at the beginning of the growing period in May and decreased thereafter while concentrations in rhizomes stayed fairly constant throughout the year and were not affected by N fertilization.Nutrient mobilization from rhizomes to shoots - defined as the maximum change in nutrient content in rhizomes from the beginning of the growth period measured in 1992/93 was 55 kg N ha-1, 8 kg P ha-1, 39 kg K ha-1 and 11 kg Mg ha-1. This is equivalent to 21 N, 36 P, 14 K and 27 Mg of the maximum nutrient content of the shoots. Nutrient remobilization from shoots to rhizomes defined as the increase in nutrient content of rhizomes between September and March measured in 1994/95 was 101 kg N ha-1, 9 kg P ha-1, 81 kg K ha-1 and 8 kg Mg ha-1 equivalent to 46 N, 50 P, 30 K and 27 Mg of nutrient content of shoots in September. Results showed that nutrient remobilization within the plant needs to be considered when calculating nutrient balances and fertilizer recommendations.     

Validation of the Principal Axis Model (PAM) and its Application to Genotype Selection in Field Pea (Pisum sativum L.) Crops

The principal axis model (PAM) uses a principal axis and anellipse to characterize the variation in the relationship betweenthe seed (SWT) and plant (PWT) weights of individual plantswithin a crop. The theoretical linkage between the magnitudeand variability of plant harvest index (PHI), and thereforeseed yield per unit area, and changes in the components of thePAM was examined using data from four field pea (Pisum sativumL.) genotypes sown at 9, 49, 100, 225 and 400 plants m^-2. Astrong linear relationship (R ²>93.8%) between SWT and PWTand a negative SWT-axis intercept were confirmed for all crops.Analyses indicated that decreased variability of PHI withina crop would result from selection to: (a ) increase the SWT-axisintercept of the PAM; (b ) increase the slope of the PAM; (c) optimize the ellipse location; and (d ) minimize the deviationaround the principal axis. The first three methods were usedto explain yield differences (P <0.05) among genotypes ofdifferent populations. A potential strategy for single plant selection based on thePAM is proposed. This may enable early generation (F₄) selectionof small, high performing plants that may be ideal crop ideotypes.A theoretical example of the strategy is presented, with differencesamong selections based on the PAM, SWT or harvest index highlighted. Field pea(Pisum sativum L.); genetic harvest index; minimum plant weight; plant harvest index; principal axis model; plant population; seed weight; selection criteria     

Transferability of microsatellite markers from Brachypodium distachyon to Miscanthus sinensis, a potential biomass crop

Miscanthus sinensis has high biomass yield and contributed two of the three genomes in M. x giganteus, a bioenergy crop widely studied in Europe and North America, and thus is a potential biomass crop and an important germplasm for Miscanthus breeding. Molecular markers are essential for germplasm evaluation, genetic analyses and new cultivar development in M. sinensis. In the present study, we reported transferability of simple sequence repeat (SSR) markers from Brachypodium distachyon to M. sinensis. A set of 57 SSR markers evenly distributed across the B. distachyon genome were deliberately designed. Out of these B. distachyon SSR markers, 86.0% are transferable to M. sinensis. The SSR loci amplified in M. sinensis were validated by re-sequencing the amplicons. The polymorphism information content (PIC) of the transferable SSR markers varied from 0.073 to 0.375 with a mean of 0.263, assessed based on 21 M. sinensis genotypes. Phylogenetic tree based on 162 alleles detected by 49 SSR markers could unambiguously distinguish B. distachyon from M. sinensis, and cluster 21 M. sinensis genotypes into three groups that are basically in coincidence with their geographical distribution and ecotype classifications. The markers developed by the comparative genomic approach could be useful for germplasm evaluation, genetic analysis, and marker-assisted breeding in Miscanthus.     

Variation of morphological and phytochemical traits in Roselle (Hibiscus sabdariffa L.) genotypes under different planting dates

Roselle (Hibiscus sabdariffa L.) is recognized as a valuable food crop due to its nutraceutical potential, rich pigment content, and medicinal properties. However, there is limited information on planting dates and suitable genotypes for roselle cultivation in arid and semi-arid regions. The objective of this field study was to investigate the influence of five planting dates (March, April, May, June, and July) on morphological and phytochemical characteristics of different roselle genotypes. Among genotypes, eight (Jiroft, Dalgan, Bampoor, Iranshahr, Nikshahr, Roodbar, Saravan, and Qaleganj) were Iranian landraces, and HA and HS-24 were originated from Ghana and Bangladesh, respectively. Planting date significantly influenced the number of branches, bolls and seeds per plant, sepal fresh weight, calyx and biomass yields, and harvest index in tested roselle landraces. The greatest morphological growth, fresh sepal weight (50.6 g plant^?1) and calyx yield (1519 kg ha^?1) were observed with the roselle planted in early May. Moreover, amounts of chlorophyll, flavonoids and antioxidant remained higher in roselle when planted between April–May. The number of branches/plant was found to be an important determinant of calyx yield (r = 0.707) in roselle. Dalgan resulted in the greatest growth and yields within a comparatively shorter period of time compared to other tested landraces. Both principal component analysis (PCA) and cluster analysis also indicated that Dalgan landrace possessed most suitable morphological and phytochemical traits among tested landraces, and therefore, it could be planted adopted for extensive cultivation settings in the arid and semi-arid regions.     

Simulating the influence of vernalization, photoperiod and optimum temperature on wheat developmental rates

Background and Aims

Accurately representing development is essential for applying crop simulations to investigate the effects of climate, genotypes or crop management. Development in wheat (Triticum aestivum, T. durum) is primarily driven by temperature, but affected by vernalization and photoperiod, and is often simulated by reducing thermal-time accumulation using vernalization or photoperiod factors or limiting accumulation when a lower optimum temperature (T_optl) is exceeded. In this study T_optl and methods for representing effects of vernalization and photoperiod on anthesis were examined using a range of planting dates and genotypes.

Methods

An examination was made of T_optl values of 15, 20, 25 and 50 °C, and either the most limiting or the multiplicative value of the vernalization and photoperiod development rate factors for simulating anthesis. Field data were from replicated trials at Ludhiana, Punjab, India with July through to December planting dates and seven cultivars varying in vernalization response.

Key Results

Simulations of anthesis were similar for T_optl values of 20, 25 and 50 °C, but a T_optl of 15 °C resulted in a consistent bias towards predicting anthesis late for early planting dates. Results for T_optl above 15 °C may have occurred because mean temperatures rarely exceeded 20 °C before anthesis for many planting dates. For cultivars having a strong vernalization response, anthesis was more accurately simulated when vernalization and photoperiod factors were multiplied rather than using the most limiting of the two factors.

Conclusions

Setting T_optl to a high value (30 °C) and multiplying the vernalization and photoperiod factors resulted in accurately simulating anthesis for a wide range of planting dates and genotypes. However, for environments where average temperatures exceed 20 °C for much of the pre-anthesis period, a lower T_optl (23 °C) might be appropriate. These results highlight the value of testing a model over a wide range of environments.Key words: Wheat, Triticum aestivum, T. durum, air temperature, thermal time, shoot apex, phenology, growth stages, anthesis, flowering     

Optimising the capacity of field trials to detect the effect of genetically modified maize on non‐target organisms through longitudinal sampling

To assess risks of cultivation of genetically modified crops (GMCs) on non‐target arthropods (NTAs), field tests are necessary to verify laboratory results and in situations where exposure pathways are very complex and cannot be reproduced in the laboratory. A central concern in the design of field trials for this purpose is whether the tests are capable of detecting differences in the abundance or activity of NTAs in a treated crop in comparison with a non‐treated comparator plot. The detection capacity of a trial depends on the abundance and variability of the taxon, the values assumed for type I (α) and II (β) errors, and the characteristics of the trial and statistical design. To determine the optimal trial layout and statistical analysis, 20 field trials carried out in Spain from 2000 to 2009 to assess risks of GMCs on NTAs were examined with α and β set at 0.05 and 0.20, respectively. In this article we aim to determine the optimal number of sampling dates during a season, or longitudinal samples, in the design of field trials for assessing effects of GM maize on NTAs, and the ones that contribute most to achieving detectable treatment effects (d_c) less than 50% of the mean of the control. Detection capacities are a function of the number of individual samples taken during the season but a high number of samples is rarely justified because gains of repeated sampling can be relatively low. These gains depend primarily on field tests relative experimental variability in individual samplings (i.e. experimental variability relative to the mean of the control in each sampling date) which in turn depends on the sampling method (visual counts, pitfall traps or yellow sticky traps) and the density (or abundance) of the taxon in question. Taxa showing more density (or abundance) have less relative experimental variability. The smaller the experimental variability, the lower the profit of increasing the number of sampling dates. Sticky traps have a good effect detection capacity and need very few sampling dates, whereas visual counts and pitfall traps have a poorer effect detection capacity and need more individual samples to achieve d_c values lower than 50%. In maize field trials, it is recommended to concentrate sampling efforts in certain growth stages; the optimal ones for achieving an acceptable detection capacity are variable but, in general, samples in the first half of the season render better detection capacity than samples in the second half.