Duration Of Vegetative Growth Research Articles

Effects of Photoperiod Treatments on Stock Plants and Cutting Rooting of Three Cultivars of Ornamental Perennials

Many species of herbaceous perennials now have numerous cultivars, with growth habits and flower colors unique to each cultivar. Vegetative propagation is required so that resulting plants are genetically identical to the parent plant. Although many cultivars are selected for precocious and vigorous flowering, it is often difficult to collect adequate vegetative cuttings from such cultivars for commercial production because juvenile (vegetative) growth is preferred for high-quality cuttings. Cuttings that are reproductive (with flower buds or flowers) can have reduced or delayed rooting and increased occurrences of fungal pathogens (especially Botrytis species), resulting in lack of crop uniformity. We sought to answer the question, can growing stock plants of herbaceous perennials under defined photoperiods extend the length of the vegetative period and enhance the rooting of cuttings harvested from these stock plants? In this study, stock plants of ‘P009S’ twinspur (Diascia integerrima), ‘Furman's Red’ sage (Salvia greggii), and ‘Wild Thing’ sage (Salvia greggii) were grown under ambient, 12-hour light, 10-hour light, and 8-hour light to determine if a particular photoperiod could be used to suppress reproductive growth by promoting vegetative growth, thereby enhancing cutting rooting success. Effects of photoperiod treatments varied among the plant cultivars studied. Plants grown under 8-hour photoperiod had longer duration of vegetative growth, smaller growth rates, and lower dry weights when compared with plants grown under 12-hour or 10-hour photoperiod. Plants grown under 12-hour photoperiod had shorter duration of vegetative growth, larger growth rates, and higher dry weights when compared with plants grown under 10-hour and 8-hour photoperiods. The probability of rooting of cuttings harvested from stock plants of ‘P009S’ twinspur, ‘Furman’s Red’ sage, and ‘Wild Thing’ sage grown under 12-hour and 10-hour photoperiods was greater when compared with cuttings harvested from stock plants grown under 8 h photoperiod.

Impact of Fertilizer Type and Vegetative Growth Duration on the Availability of Copper in Clay Loam Soil Planted of Maize (Zea mays L.) in Iraq

The present field trial aimed to study the effect of fertilizer type and growth duration on copper availability in the maize soil. In addition to the control, six different fertilizer treatments of mineral fertilizers, organic fertilizers, and humic acid (two levels each) were applied in the experiment. Soil samples were collected 70 and 100 days after planting. The results present that there were no significant differences between the half-recommendation fertilizer treatments (the first level) for all fertilizers, and the effect of the entire recommendation treatments (the second level) for poultry waste and humic acid 0.37 mg kg-1 and their superiority over the urea fertilization treatments 0.33 mg kg-1 in 70 days of cultivation. At 100 days, the fertilization treatments with poultry waste resulted in the highest concentration of available copper, 0.41 and 0.35 mg kg-1, respectively, the two levels. The results present a decrease in the concentration of available copper in the soil with an increase in the growth period.

The Effects of Phased Warming during Late Winter and Early Spring on Grain Yield and Quality of Winter Wheat (Triticum aestivum L.)

Phased warming in late winter and early spring can increase winter wheat grain yield. However, the effects of different durations of warming during this period on winter wheat grain yield and quality are not yet clear. Therefore, this study conducted field warming experiments in a movable polyethylene greenhouse during the late winter and early spring stages of the three wheat growing seasons from 2019 to 2022. The results showed that the accumulated growing degree days (GDD) of the warming treatment during the warming period were increased by 87.3–215.7 °C d compared to the control (CK). The warming treatment advanced and prolonged the duration of vegetative growth and spike differentiation after regreening, promoted spike and flower development, and increased grain length, grain width, and grain area. During the three growing seasons, the longer the warming duration (WD) of the warming treatment, the more obvious were the observed promoting effects on the kernel number per spike and 1000-kernel weight. From 2019 to 2021, compared to the CK, the spike number per unit area and grain yield of the warming treatments increased with the prolongation of WD. However, in the 2022 growing season the spike number per unit area and grain yield of the warming treatment were increased with longer WD, reaching the maximum at WD of 56 days and then gradually decreasing with longer WD. Compared to CK, the grain protein content, wet gluten content, and sedimentation value of the warming treatment decreased with the prolongation of WD. The promotion effect of longer WD on grain starch content and protein yield was more significant. In summary, the accumulated GDD during the warming period compared to CK was 155.8–181.2 °C d, and at WD of 50–56 days a relatively higher grain yield and protein yield could be obtained.

Prediction of heading date, culm length, and biomass from canopy-height-related parameters derived from time-series UAV observations of rice.

Unmanned aerial vehicles (UAVs) are powerful tools for monitoring crops for high-throughput phenotyping. Time-series aerial photography of fields can record the whole process of crop growth. Canopy height (CH), which is vertical plant growth, has been used as an indicator for the evaluation of lodging tolerance and the prediction of biomass and yield. However, there have been few attempts to use UAV-derived time-series CH data for field testing of crop lines. Here we provide a novel framework for trait prediction using CH data in rice. We generated UAV-based digital surface models of crops to extract CH data of 30 Japanese rice cultivars in 2019, 2020, and 2021. CH-related parameters were calculated in a non-linear time-series model as an S-shaped plant growth curve. The maximum saturation CH value was the most important predictor for culm length. The time point at the maximum CH contributed to the prediction of days to heading, and was able to predict stem and leaf weight and aboveground weight, possibly reflecting the association of biomass with duration of vegetative growth. These results indicate that the CH-related parameters acquired by UAV can be useful as predictors of traits typically measured by hand.

How seeds and growth dynamics influence plant size and yield: Integrating trait relationships into ontogeny

Abstract Seeds, growth rates and duration of growth influence plant development. However, we lack a mechanistic understanding of how they lead to larger and higher‐yielding plants, as these traits have not yet been explicitly studied in combination and across ontogeny. Seed size and growth dynamics have evolved differently during domestication and improvement. Nevertheless, it remains unclear whether the relationships between these traits and their contribution to plant size and yield have also changed over the course of crop evolution. Here we grew wild, landrace and improved accessions of 18 annual herbaceous crops in a glasshouse. For each plant, we measured seed mass, growth rate and duration of vegetative growth. We also measured plant size at three ontogenetic stages: seedling, juvenile and mature, and reproductive output. Using path analyses, we tested causal relationships between the traits and quantified their relative importance in determining mature plant size and yield. Seed mass and duration of vegetative growth were more important than growth rates in explaining variations in mature plant size and yield among species. Domesticated plants were larger, had heavier seeds and higher yields, but did not grow faster or for longer time‐spans than their wild progenitors. Trait relationships did not differ between the wild, landrace and improved accessions. Our results suggest that annual herbs reach larger sizes primarily through a combination of heavier seeds and longer vegetative growth periods. Moreover, domestication has increased plant size only through the heavy‐seed causal pathway, via cascading effects during ontogeny. However, the high yields of modern crops hardly be explained by the traits considered here, suggesting the importance of other drivers, such as roots and their microbiome. Synthesis. We provide a better mechanistic understanding of the size axis of global plant trait variation and emphasise the role of growth duration in explaining the diversity of mature plant sizes. Seeds and growth dynamics are highly functionally coordinated with plant size, and this coordination has changed little during crop evolution. Our results highlight that multi‐trait relationships throughout plant ontogeny play a key role in governing how domestication has influenced plant size and crop yields.

Growth and Yield Responses of Rice Genotypes Subjected to Water Deficit in Varied Soil Types

Inconsistent results were obtained on the yield of rice genotypes established along the soil toposequence thus the need to validate these under controlled environment with rice genotypes. This investigation hypothesised there could be variation in the growth and yield of rice genotypes in different soil types under soil water deficit. A pot experiment was established in an open screen house, Ibadan. The treatment consisted of rice varieties (IR 64, IR 77298-14-1-2-B-10, NERICA 4 and WAB 56-104), soil ecologies [hydromorphic (H), lowland (L) and upland soils (U)] and soil moisture regime (Control and water deficit stress), in completely randomised design replicated three times. Growth in rice genotypes were significantly higher under optimum water supply than under water deficit. Conversely, rice genotypes under water deficit flowered later and had significantly higher spikelet sterility than under optimum water supply. Number of tillers plant-1 was in the order H > L > U. However, 1000 grain mass was in the order U > H > L. IR 64 had the highest grain yield. Similar pattern was observed on the shoot biomass, number of tillers and number of panicles. In different soil ecologies under water deficit, IR 64 and IR 77298-14-1-2-B-10 had significantly the highest number of panicles plant-1. These evidences suggested that high number of tillers observed in hydromorphic soil is associated with the duration of vegetative growth. Isohydric behaviour was not maintained by rice genotypes used as reflected in the variation in number of panicles under water deficit in the soil types.

Diversity in Phenological and Agronomic Traits of Miscanthus sinensis Collected in Korea and Eastern Asia

Four-year field experiments were conducted to investigate phenotypic traits associated with the biomass yield of 173 Miscanthus sinensis accessions collected from Korea and neighboring East Asian countries. Nine phenological and agronomic traits associated with biomass yield were assessed to investigate their phenotypic diversity and relationships with biomass yield as well as the latitudes of the M. sinensis accessions collection sites. Correlation analyses among phenological and agronomic traits, biomass yield, and collection site revealed that heading date, vegetative growth duration, leaf area, and stem growth traits (stem height, stem diameter, and stem dry weight) were closely related to biomass yield. The latitude of collection site exhibited a significant negative correlation with heading date, and heading date showed a significant positive correlation with biomass yield, indicating the high biomass potential of the accessions originating from lower latitude due to longer vegetative growth. The best biomass yield was mainly observed in M. sinensis accessions from the southern parts of Korea, such as Jeolla and Jeju provinces, with over 20 Mg DM ha−1. Agronomic traits measured in the second year after planting also showed a high correlation with biomass yield measured in the fourth year after planting. In particular, vegetative growth duration, leaf area, stem diameter, and stem dry weight measured in the second year were significantly related to the fourth-year biomass yield. Therefore, these findings suggest that agronomic traits measured in the second year can be used for screening M. sinensis genetic resources and breeding lines with high biomass yield potential.

Assessment of Genotypes and Management Strategies to Improve Resilience of Winter Wheat Production

Climate is a main factor that influences the winter wheat production. Changing the crop cultivars and adjusting the sowing dates are used as strategies to adapt to climate change. First, we evaluated the simulation ability of the Decision Support System for Agro-technology Transfer (DSSAT) CERES wheat model based on the experimental data with varied sowing dates and cultivars. Second, we designed optimal cultivars in three different environmental conditions with the highest grain yield in the North China Plain (NCP) based on model sensitivity analysis. Furthermore, we optimized the sowing dates for three sites with the above-derived cultivar parameters. The results showed that the DSSAT–CERES wheat model was suitable for winter wheat simulation after calibration and validation with a Normalized Root Mean Square Error (NRMSE) between 0.9% and 9.5% for phenology, 6.8% and 17.8% for above ground biomass, and 4.6% and 9.7% for grain yield. The optimal cultivars significantly prolonged the wheat growth duration by 14.1, 27.5, and 24.4 days at the Shangzhuang (SZ), Xingtai (XT), and Zhumadian (ZMD) sites compared with current cultivars, respectively. The vegetative growth duration (from sowing to anthesis) was prolonged 18.4 and 12.2 days at the XT and ZMD sites significantly, while shortened 0.81 days at the SZ site. The grain yield could be potentially improved by 29.5%, 86.8%, and 34.6% at the SZ, XT, and ZMD sites using the optimal cultivars, respectively. Similarly, the improvement of aboveground biomass at three sites was 5.5%, 47.1%, and 12.7%, respectively. Based on the guaranteed rate and analysis of variance, we recommended a later sowing date (from 15 September to 20 October) at the SZ and ZMD sites, and 15 September to 15 October at the XT site. In addition, the methodology of this study could be expanded to other regions and possibly to other crops.

Variation in Root and Shoot Growth in Response to Reduced Nitrogen.

Recently, root traits have been suggested to play an important role in developing greater nitrogen uptake and grain yield. However, relatively few breeding programs utilize these root traits. Over a series of experiments at different growth stages with destructive plant biomass measurements, we analyzed above-ground and below-ground traits in seven geographically diverse lines of wheat. Root and shoot biomass allocation in 14-day-old seedlings were analyzed using paper roll-supported hydroponic culture in two Hoagland solutions containing 0.5 (low) and 4 (high) mM of nitrogen (N). For biomass analysis of plants at maturity, plants were grown in 7.5 L pots filled with soil mix under two nitrogen treatments. Traits were measured as plants reached maturity. High correlations were observed among duration of vegetative growth, tiller number, shoot dry matter, and root dry matter. Functionality of large roots in nitrogen uptake was dependent on the availability of N. Under high N, lines with larger roots had a greater yield response to the increase in N input. Under low N, yields were independent of root size and dry matter, meaning that there was not a negative tradeoff to the allocation of more resources to roots, though small rooted lines were more competitive with regards to grain yield and grain N concentration in the low-N treatment. In the high-N treatment, the large-rooted lines were correlated to an increase in grain N concentration (r = 0.54) and grain yield (r = 0.43). In low N, the correlation between root dry matter to yield (r = 0.20) and grain N concentration (r = −0.38) decreased. A 15-fold change was observed between lines for root dry matter; however, only a ~5-fold change was observed in shoot dry matter. Additionally, root dry matter measured at the seedling stage did not correlate to the corresponding trait at maturity. As such, in a third assay, below-ground and above-ground traits were measured at key growth stages including the four-leaf stage, stem elongation, heading, post-anthesis, and maturity. We found that root growth appears to be stagnant from stem elongation to maturity.

Multi-trait analysis of domestication genes in Cicer arietinum – Cicer reticulatum hybrids with a multidimensional approach: Modeling wide crosses for crop improvement

Domestication and subsequent breeding have eroded genetic diversity in the modern chickpea crop by ˜100-fold. Corresponding reductions to trait variation create the need, and an opportunity, to identify and harness the genetic capacity of wild species for crop improvement. Here we analyze trait segregation in a series of wild x cultivated hybrid populations to delineate the genetic underpinnings of domestication traits. Two species of wild chickpea, C. reticulatum and C. echinospermum, were crossed with the elite, early flowering C. arietinum cultivar ICCV96029. KASP genotyping of F2 parents with an FT-linked molecular marker enabled selection of 284 F3 families with reduced phenological variation: 255 F3 families of C. arietinum x reticulatum (AR) derived from 17 diverse wild parents and 29 F3 families of C. arietinum x echinospermum (AE) from 3 wild parents. The combined 284 lineages were genotyped using a genotyping-by-sequencing strategy and phenotyped for agronomic traits. 50 QTLs in 11 traits were detected from AR and 35 QTLs in 10 traits from the combined data. Using hierarchical clustering to assign traits to six correlated groups and mixed model based multi-trait mapping, four pleiotropic loci were identified. Bayesian analysis further identified four inter-trait relationships controlling the duration of vegetative growth and seed maturation, for which the underlying pleiotropic genes were mapped. A random forest approach was used to explore the most extreme trait differences between AR and AE progenies, identifying traits most characteristic of wild species origin. Knowledge of the genomic basis of traits that segregate in wild-cultivated hybrid populations will facilitate chickpea improvement by linking genetic and phenotypic variation in a quantitative genetic framework.

Characterisation of ten commercial sorghum genotypes grown under water-limited conditions for bioenergy production in Mediterranean environment

The evaluation of commercial hybrids under limited water availability is of primary importance to assess Sorghum bicolor (Moench) as potential multipurpose bioenergy crop in Mediterranean drought prone environments. Ten genotypes were grown during three growing seasons (2010, 2011 and 2012) in open field trials and in pot experiments (2014). Phenological traits, biomass production, fibre content and biomass chemical composition were measured under irrigated and rainfed conditions. Differences in biomass production among the ten genotypes varied across years. In a three-year experiment significant differences were found among the ten genotypes in terms of duration of vegetative growth (P<0.05) and aboveground dry biomass production (P<0.1) in response to irrigated and rainfed conditions. Among the ten genotypes analysed, the hybrid ABF306 stands for its performance in terms of biomass production and chemical composition. In fact, it showed the lowest biomass yield reduction when grown under rainfed conditions, the highest drought tolerance index (=0.9), a °Brix value comparable to that of sweet sorghum genotypes (8.8 °Brix under rainfed conditions), lignin content that was not statistically influenced by water availability, and a lignin cellulose ratio (0.087) favourable for biogas production. The shoot transpiration efficiency and the total transpiration efficiency recorded at high (Exp1) and low (Exp2) vapour pressure deficit were comparable, and sometimes higher, to that of commercial sorghum hybrids. All these characteristics make ABF306 a suitable candidate for bioenergy production in Mediterranean drought prone environments.

Changes in developmental duration of direct-seeded rice in a well-drained paddy field in response to late planting

We investigated changes in the developmental duration of rice cultivars with a wide range of maturities in response to late planting. Elucidating the relationship between cropping season and the progress of growth stages is important for establishing direct-seeded cultivation and creating growth models. Late planting of the intermediate to late maturing cultivars Akidawara and Hoshijirushi decreased the time from emergence to panicle formation and decreased the cumulative effective temperature (CET) and cumulative effective soil temperature (CEST). In the very early maturing cultivars Ichibanboshi and Fusakogane, the changes in number of days, CET, and CEST from emergence to panicle formation with late planting were small. From emergence to heading and maturity, the number of days, CET, and CEST of many cultivars tended to increase until mid-May and then decreased. The changes in the number of days, CET, and CEST caused by late planting were greater for the intermediate to late maturing cultivars than for the very early maturing cultivars. The differences between cultivars were greatest with early May sowing, and then decreased with later planting. Short-day condition revealed significant differences in the duration of vegetative growth and CET among cultivars, but long-day condition erased these differences. These results demonstrate that the photosensitivity and thermosensitivity of cultivars are especially important in crop planning and for creating growth models of direct-seeded rice.

Synthetic control of flowering in rice independent of the cultivation environment.

For genetically homogeneous crops, the timing of flowering is determined largely by the cultivation environment and is strongly associated with the yield and quality of the harvest1. Flowering time and other agronomical traits are often tightly correlated, which can lead to difficulty excluding the effects of flowering time when evaluating the characteristics of different genetic varieties2. Here, we describe the development of transgenic rice plants whose flowering time can be controlled by specific agrochemicals. We first developed non-flowering rice plants by overexpressing a floral repressor gene, Grain number, plant height and heading date 7 (Ghd7)3,4, to inhibit any environmentally induced spontaneous flowering. We then co-transformed plants with a rice florigen gene, Heading date 3a (Hd3a)5, which is induced by the application of specific agrochemicals. This permitted the flowering time to be experimentally controlled regardless of the cultivation environment: some transgenic plants flowered only after agrochemical treatment. Furthermore, plant size and yield-related traits could, in some cases, be increased owing to both a longer duration of vegetative growth and an increased panicle size. This ability to control flowering time experimentally, independently of environmental variables, may lead to production of crops suitable for growth in different climates and facilitate breeding for various agronomical traits.

Bioenergy Sorghum Crop Model Predicts VPD-Limited Transpiration Traits Enhance Biomass Yield in Water-Limited Environments.

Bioenergy sorghum is targeted for production in water-limited annual cropland therefore traits that improve plant water capture, water use efficiency, and resilience to water deficit are necessary to maximize productivity. A crop modeling framework, APSIM, was adapted to predict the growth and biomass yield of energy sorghum and to identify potentially useful traits for crop improvement. APSIM simulations of energy sorghum development and biomass accumulation replicated results from field experiments across multiple years, patterns of rainfall, and irrigation schemes. Modeling showed that energy sorghum's long duration of vegetative growth increased water capture and biomass yield by ~30% compared to short season crops in a water-limited production region. Additionally, APSIM was extended to enable modeling of VPD-limited transpiration traits that reduce crop water use under high vapor pressure deficits (VPDs). The response of transpiration rate to increasing VPD was modeled as a linear response until a VPD threshold was reached, at which the slope of the response decreases, representing a range of responses to VPD observed in sorghum germplasm. Simulation results indicated that the VPD-limited transpiration trait is most beneficial in hot and dry regions of production where crops are exposed to extended periods without rainfall during the season or to a terminal drought. In these environments, slower but more efficient transpiration increases biomass yield and prevents or delays the exhaustion of soil water and onset of leaf senescence. The VPD-limited transpiration responses observed in sorghum germplasm increased biomass accumulation by 20% in years with lower summer rainfall, and the ability to drastically reduce transpiration under high VPD conditions could increase biomass by 6% on average across all years. This work indicates that the productivity and resilience of bioenergy sorghum grown in water-limited environments could be further enhanced by development of genotypes with optimized VPD-limited transpiration traits and deployment of these crops in water limited growing environments. The energy sorghum model and VPD-limited transpiration trait implementation are made available to simulate performance in other target environments.

Variable Responses to CO<sub>2</sub> of the Duration of Vegetative Growth and Yield within a Maturity Group in Soybeans

Prior experiments in indoor chambers and in the field using free-air carbon dioxide enrichment (FACE) systems indicated variation among soybean cultivars in whether and how much elevated CO2 prolonged vegetative development. However, the cultivars tested differed in maturity group, and it is not known whether variation exists in CO2 effects on the duration of vegetative growth within a maturity group. In these experiments, a total of five soybean cultivars of maturity group IV were grown at ambient and elevated CO2 in the field in Maryland, USA using FACE systems, over three years. The time of first flowering, the time of the first open flowers at the apex of the main stem, the total number of main stem nodes at maturity, and seed yield were recorded. In each year of the study, there were cultivars in which elevated CO2 did not affect the duration of vegetative growth or the main stem node number, and other cultivars in which elevated CO2 prolonged vegetative growth and increased the number of main stem nodes and seed yield at maturity. The stimulation in yield by elevated CO2 was highly correlated with the increase in the number of main stem nodes, indicating that CO2 effects on the duration of vegetative growth may be important in adapting soybean to higher atmospheric CO2.

Elevated Carbon Dioxide Effects on Reproductive Phenology and Seed Yield among Soybean Cultivars

ABSTRACTSeed yield increases in soybean [Glycine max (L.) Merr.] caused by increased growth at elevated carbon dioxide concentrations primarily result from increased numbers of pods. Reasons for differences among cultivars in the increases in pod number are not clear. In experiments in controlled environment chambers, cultivars varied in how much elevated carbon dioxide delayed the transition of the apical node of the main stem from vegetative to reproductive growth. The longer the delay in the transition, the more main stem and total nodes and pods were produced, increasing the relative stimulation of seed yield. In free‐air carbon dioxide enrichment (FACE) systems in the field, the timing of the first open flower, and the rate of progression through reproductive stages was faster, slower, or unchanged by elevated carbon dioxide in three indeterminate cultivars. However, independently from these effects on the rate of progression through the flowering stages, elevated carbon dioxide concentration also differentially affected the overall duration of vegetative growth, and the number of main stem and total nodes and pods produced. The extension of the duration of vegetative growth caused by elevated carbon dioxide was highly correlated with the relative seed yield increase in the field, as well as in the controlled environment chamber experiments.

Dry matter yield and radiation use efficiency of four autumn sown top flowering annual clovers

Monocultures of arrowleaf (Trifolium vesiculosum), balansa (T. michelianum), gland (T. glanduliferum) and Persian (T. resupinatum) clovers were sown on four dates in autumn and winter 2010. Dry matter (DM) accumulation was dependent on the duration of crop growth which was influenced by the time of sowing. Autumn sown crops which flowered latest had a longer duration of vegetative growth and consequently produced the highest dry matter yields. In the establishment year, autumn sown crops produced up to 17.5 t DM/ha for balansa, 12.5 t DM/ha for Persian, 11.0 t DM/ha for gland and 9.4 t DM/ha for arrowleaf at physiological maturity (P

Physiological and Phenological Responses of Historical Soybean Cultivar Releases to Earlier Planting

ABSTRACTThe trend toward earlier soybean [Glycine max (L.) Merr.] planting in the midwestern United States has interacted synergistically with genetic yield gain to provide improvement in on‐farm yields. However, the impacts of earlier planting dates and their interaction with genetic gain in physiological and phenological traits remain unclear. The objectives of this study were to determine if a 30‐d difference in planting date affected measured rates of genetic improvement in (i) total dry matter (TDM) production, (ii) harvest index (HI), and (iii) growth‐stage duration in the north‐central United States. Research was conducted at Arlington, WI, Urbana, IL, and Lafayette, IN during 2010 and 2011 using 59 Maturity Group (MG) II cultivars (released 1928–2008) at Wisconsin, and 57 MG III cultivars (released 1923–2007) at Illinois and Indiana, with targeted planting dates of 1 May and 1 June. A mixed‐effect regression analysis was used to model genetic change in TDM, HI, and growth stage duration as impacted by planting date. Breeding efforts have increased TDM(R7), HI, seed‐fill duration (SFD), and reproductive growth duration over time, as vegetative growth duration has been reduced. Early planting provided increased TDM(R7) and longer reproductive growth duration, but had no effect on HI or SFD. A synergistic planting date × year of release interaction existed for TDM(R7) in both maturity groups, but not for HI or SFD, suggesting that the higher yields in newer, early‐planted cultivars resulted from greater TDM production, not improved HI or SFD.

Multivariate analysis of quantitative traits can effectively classify rapeseed germplasm

In this study, the use of different multivariate approaches to classify rapeseed genotypes based on quantitative traits has been presented. Tree regression analysis, PCA analysis and two-way cluster analysis were applied in order todescribe and understand the extent of genetic variability in spring rapeseed genotype by trait data. The traits which highly influenced seed and oil yield in rapeseed were successfully identified by the tree regression analysis. Principal predictor for both response variables was number of pods per plant (NP). NP and 1000 seed weight could help in the selection of high yielding genotypes. High values for both traits and oil content could lead to high oil yielding genotypes. These traits may serve as indirect selection criteria and can lead to improvement of seed and oil yield in rapeseed. Quantitative traits that explained most of the variability in the studied germplasm were classified using principal component analysis. In this data set, five PCs were identified, out of which the first three PCs explained 63% of the total variance. It helped in facilitating the choice of variables based on which the genotypes? clustering could be performed. The two-way cluster analysissimultaneously clustered genotypes and quantitative traits. The final number of clusters was determined using bootstrapping technique. This approach provided clear overview on the variability of the analyzed genotypes. The genotypes that have similar performance regarding the traits included in this study can be easily detected on the heatmap. Genotypes grouped in the clusters 1 and 8 had high values for seed and oil yield, and relatively short vegetative growth duration period and those in cluster 9, combined moderate to low values for vegetative growth duration and moderate to high seed and oil yield. These genotypes should be further exploited and implemented in the rapeseed breeding program. The combined application of these multivariate methods can assist in deciding how, and based on which traits to select the genotypes, especially in early generations, at the beginning of a breeding program.

Energy sorghum hybrids: Functional dynamics of high nitrogen use efficiency

The nitrogen use efficiency (NUE) of high biomass energy sorghum hybrid plants increased during 180 days of growth to a maximum of 370 g DW g−1 N−1. Shoot N uptake was biphasic and continued for 120 days. Leaf N accumulation was rapid until day 60. Specific leaf nitrogen (SLN) varied from 0.9 to 1.7 g N m−2 green leaf area, a typical range for C4 grass canopies. Stem N increased to a maximum at day 120. NUE increased during development in parallel with increasing stem to leaf biomass ratio and as stems decreased from 0.7% to 0.2% N. At the end of the season, green leaves were ∼1% N, represented 17% of total shoot biomass and accounted for 50% of N present in shoots (above ground biomass) while stems were ∼0.2% N, comprised 83% of shoot biomass and accounted for 50% of shoot N. High NUE was due in part to N-remobilization from lower leaves and stem nodes/internodes to upper portions of the canopy. Up to 70% of dry weight and 90% of N was remobilized during senescence of lower leaves and 70% of N was remobilized from lower stem nodes/internodes. The NUE of energy sorghum was similar to Saccharum officinarum and Miscanthus x giganteus, and higher than grain Sorghum bicolor, Zea mays, and Panicum virgatum. High NUE of energy S. bicolor is due to long duration of vegetative growth, high stem to leaf biomass ratio, and very efficient N-remobilization from lower leaves and stem internodes during development.