Genetic variation of Amaranthus retroflexus L. and Chenopodium album L. (Amaranthaceae) suggests multiple independent introductions into Iran

Amaranthus retroflexus L. and Chenopodium album L. (Amaranthaceae) are weedy plants that cause severe ecological and economic damage. In this study, we collected DNA from three different countries and assessed genetic diversity using inter-simple sequence repeat (ISSR) markers. Our analysis shows both weed species have low genetic diversity within a population and high genetic diversity among populations, as well as a low value of gene flow among the populations. UPGMA clustering and principal coordinate analysis indicate four distinct groups for A. retroflexus L. and C. album L. exist. We detected significant isolation-by-distance for A. retroflexus L. and no significant correlation for C. album L. These conclusions are based data from 13 ISSR primers where the average percentage of polymorphism produced was 98.46 % for A. retroflexus L. and 74.81% for C. album L.. These data suggest that each population was independently introduced to the location from which it was sampled and these noxious weeds come armed with considerable genetic variability giving them the opportunity to manifest myriad traits that could be used to avoid management practices. Our results, albeit not definitive about this issue, do not support the native status of C. album L. in Iran

Evaluation of techniques to break seed dormancy in Redroot pigweed (Amaranthus retroflexus)

If we understand factors that trigger seed dormancy release, then we can accurately predict whether the seed will remain dormant or germinate out of the seed bank. With regards to annual weed species, detailed understanding of what breaks seed dormancy is therefore critical for determining how many weed seeds will germinate into problematic weeds. To investigate the breaking of dormancy in weed seeds, we conducted an experiment with Redroot pigweed (Amaranthus retroflexus). Dormant seeds were treated with cold stratification (4 °C for 30 days), application of gibberellic acid (at 500, 1000, 1500, and 2000 parts per million) or ultrasound (for 10, 20, 30, and 40 minutes), soaking in hot water (90 °C for 3, 5, 7 and 10 minutes) or 98% sulfuric acid (for 1, 2 and 3 minutes) to determine which treatment most effectively broke dormancy. The results showed that Redroot pigweed seed dormancy was effectively broken by cold stratification, gibberellic acid, or ultrasound. Short treatments with hot water had minimal effect while longer times or treatment with sulfuric acid eliminated seed germination. In addition to germination percentage, germination rate, plumule length, radicle length, seedling length, seedling dry weight, and seed vigor index were also measured; similarly application of gibberellic acid had the most significant effect on these parameters. The results of this study add to our understanding of what processes effectively or ineffectively break Redroot pigweed seed dormancy and promote growth

Redroot pigweed (Amaranthus retroflexus L.) and lamb's quarters ‎‎(Chenopodium album L.) populations exhibit a high degree of ‎morphological and biochemical diversity

Amaranthus retroflexus L. and Chenopodium album L. are noxious weeds that have a cosmopolitan distribution. These species successfully invade and are adapted to a wide variety of diverse climates. In this paper we evaluated the morphology and biochemistry of 16 populations of A. retroflexus L. and 17 populations of C. album L.. Seeds from populations collected from Spain, France and Iran were grown together at the experimental field of the agriculture research of University of Mohaghegh Ardabili and a suite of morphological traits and biochemical traits were assessed. Among the populations of A. retroflexus L. and of C. album L. were observed significant differences for all the measured traits. The number of branches for A. retroflexus L. (12.22) and inflorescence length (14.34) for C. album L. were the two characteristics that exhibited the maximum coefficient of variation. Principal component analysis of these data identified four principal components for each species that explained 83.54 (A. retroflexus L.) and 88.98 (C. album L.) of the total variation. A dendrogram based on unweighted neighbor-joining method clustered all the A. retroflexus L. and C. album L. into two main clusters and four sub-clusters. Canonical correlation analysis was used to evaluate relationships between climate classification of origin and traits. Similarly, the measured characteristics did not group along Köppen climate classification. Both analyses support the conclusion that A. retroflexus L. and C. album L. exhibit high levels of diversity despite similar environmental histories. Both species also exhibit a high diversity of the measured biochemical compounds indicating they exhibit different metabolic profiles even when grown concurrently and sympatrically. Several of the biochemical constituents identified in our study could serve as effective indices for indirect selection of stresses resistance/tolerance of A. retroflexus L. and C. album L. The diversity of the morphological and biochemical traits observed among these populations illustrates how the unique selection pressures faced by each population can alter the biology of these plants. This understanding provides new insights to how these invasive plant species successfully colonize diverse ecosystems and suggests methods for their management under novel and changing environmental conditions

Composite patch reinforcement of a cracked simply-supported beam traversed by moving mass

In this study dynamic analysis of a metallic beam under travelling mass was investigated. A beam with an edge crack was considered to be reinforced using composite patch. Euler-Bernoulli beam theory was applied to simulate the time-history behavior of the beam under dynamic loading. Crack in the beam was modeled using a rotational spring. Dimension of the composite patch, crack length, stress intensity factor at crack tip and beam deflection are some parameters which were studied in details. Results were validated against those which were found through Finite Element Method

Crack propagation modeling using Peridynamic theory

Crack propagation and branching are modeled using nonlocal peridynamic theory. One major advantage of this nonlocal theory based analysis tool is the unifying approach towards material behavior modeling- irrespective of whether the crack is formed in the material or not. No separate damage law is needed for crack initiation and propagation. This theory overcomes the weaknesses of existing continuum mechanics based numerical tools (e.g. FEM, XFEM etc.) for identifying fracture modes and does not require any simplifying assumptions. Cracks grow autonomously and not necessarily along a prescribed path. However, in some special situations such as in case of ductile fracture, the damage evolution and failure depend on parameters characterizing the local stress state instead of peridynamic damage modeling technique developed for brittle fracture. For brittle fracture modeling the bond is simply broken when the failure criterion is satisfied. This simulation helps us to design more reliable modeling tool for crack propagation and branching in both brittle and ductile materials. Peridynamic analysis has been found to be very demanding computationally, particularly for real-world structures (e.g. vehicles, aircrafts, etc.). It also requires a very expensive visualization process. The goal of this paper is to bring awareness to researchers the impact of this cutting-edge simulation tool for a better understanding of the cracked material response. A computer code has been developed to implement the peridynamic theory based modeling tool for two-dimensional analysis. A good agreement between our predictions and previously published results is observed. Some interesting new results that have not been reported earlier by others are also obtained and presented in this paper. The final objective of this investigation is to increase the mechanics knowledge of self-similar and self-affine cracks.This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Assessment of Performance the Recorded Herbicides in Rice (Oryza sativa) to Control Weed Species in Raton

This experiment was conducted to evaluate the performance of different herbicides on weed control and yield of ratoon rice as a randomized complete block design with four replications during 2012 at the Pasha Cola village of Sari- Iran. The treatments were: Anilofos+ Ethoxysulfuron (3 lit ha-1), Butachlor (3 lit ha-1) + Cinosulfuron (100 g ha-1), Bensulfuron methyl (75 g ha-1) + Butachlor (3 lit ha-1), Butachlor (3 lit ha-1), Cinosulfuron (100 g ha-1), Bensulfuron methyl (75 g ha-1) with a two-step weeding and weedy treatment (control). Results showed that the Sulfonylurea group herbicides such as Cinosulfuron and Bensulfuron methyl reduced density and dry weight of weed on the one hand and density and dry weight of weed in total on the other hand during the growing season. This leads to increase in ratoon rice yield at the end of the growing season. In addition to results showed that the Butachlor does not affected density and dry weight of weeds it caused reduction in weight of 1000 grain and yield of ratoon rice

Predicting Emergence of the Most Important Weed Species in Soybean (Glycine max L.) under Different Management Operation

Introduction: Summer annual weeds typically germinate in spring and early summer, grow throughout the summer, and set seeds by fall. Summer annual weeds are a persistent problem in summer annual row crops, competing directly for water, light, and nutrients, causing yield losses in quantity and quality. Although agriculture is increasingly relying on modern technology, knowledge of the biological systems in which these technologies are used is still critical for implementation of management strategies. Biological information about weeds is valuable and necessary for developing management strategies to minimize their impact. Scouting fields for pest problems are essential in any cropping system and knowledge of the timing and sequence of weed species emergence could increase the effectiveness of weed scouting trips and subsequent management practices. The success of any annual plant is directly correlated to its time of seedling emergence because it determines the ability of a plant to compete with its neighbors, survive biotic and abiotic stresses, and reproduce. The period and pattern of emergence of the weed community depend on the species present in the seed bank and their interaction with the environment. Therefore, knowledge of the weed species present in the soil seed bank and when these species are most likely to emerge is important in planning effective weed control programs. Temperature has been reported to be the main environmental factor regulating germination and emergence of weed species. Scientists have developed TT models to predict the emergence of weed species based on a daily accumulation of heat units or growing degree days (GDD) above a minimum base threshold value (Tbase). The predictive models for weed emergence based on the accumulation of TT appear to be accurate enough for projections of weed emergence time (Grundy 2003). Moreover, soil temperature data are easily accessible, making this type of model practical and useful to farmers. Many studies of weed growth, and thus predicting models for areas outside of Mazandaran is performed as a particular study. Because the differences in soil conditions, climatic, geographic and weed species there is a possibility that these models are not appropriate to predict weed species in Mazandaran province. Furthermore, the purpose of this experiment is investigation growth of weeds and develops an empirical model based on GDD to predicting the growth of several species of summer weeds in soybean. Materials and methods: The experiment was conducted as split split-plot in a randomized complete block design with three replications in the summer of 2016 in Dasht-e-Naz Company Sari-Iran with geographical coordinates 36º 39´ N 53º 11´ E, and 1 meters above sea level. The treatments included two tillage system (No Tillage, Tillage), three densities of 20, 30 and 40 plants per square meter of soybeans and Pursuit-doses (imazethapyr) (0, 50%, 75%, standard dose and 25% of the standard dose, respectively). To predict the growth pattern in each plot a fixed 50 × 50 cm quadrat fixed in the center of each plot and since the beginning of the season and after the first irrigation, counting of new grown seedlings was began based on weeds species. The Counting was performed weekly and then counted seedlings were eliminated after in any stage as long as new emergence was not seen. Non-linear regression (Sigma Plot 12.5) was used for the expression pattern of cumulative emergence of seedlings. The 3 parameter logistic function was fitted to the data. where y represents the predicted cumulative percent emergence, X0, GDD to reach the %50 cumulative emergence, a is the upper asymptote (theoretical maximum percent emergence), b is the slope of the curve. We considered that soil water was not a limiting factor for weed emergence, using soil temperature (growing degree days, GDD) as the only independent variable for predicting cumulative emergence. Thus, GDD were calculated with the soil temperatures by using the formula: where Tmax and Tmin are the daily maximum and minimum temperature, respectively, and Tb is the base temperature. Base temperatures used in the calculations of GDD were: 9.0ºC for A. theophrasti, 12.0ºC for S. halepense, 22.3ºC for A. retroflexus, 8.1ºC for E. maculate, 7.5ºC for P. oleracea, 4.0ºC for B. napus. From the emergence count data, mean emergence time (MET) and emergence rate index (ERI) were calculated as follows: where N1, ..., Nn is the number of newly emerged seedlings since the time of the previous count, t1, ..., tn are the GDD after sowing, and n is the number of sampling occasions. These two indices give us a simple indication of the emergence process, providing a useful tool to compare the progress of seedling emergence of each species in the two sites. However, they cannot provide more detailed information on emergence duration and speed. Results and Discussion: The results showed that except sorghum that in tillage treatment had the lowest cumulative emergence, other species in no-tillage treatment had the lowest cumulative emergence. At the end of the sampling patterns of emergence has been specified, all species of weeds, in the density of 40 plants per square meter of soybean and dose of 1.25 liter per hectare of herbicide Pursuit had the lowest cumulative emergence and in the density of 20 plants per square meter of soybean and dose of 0 liters per hectare of herbicide Pursuit had the maximum cumulative emergence. Among other species, Amaranthus retroflexus needed the lowest mean emergence time (MET) and the lowest growing degree days (GDD) to reach 50% emergence. Whereas, among the species, Abutilon theophrasti needed maximum mean emergence time (MET) and maximum growing degree days (GDD) to reach 50% emergence. On this basis, growth stage suitable for controlling pigweed, when the main wave of seedlings of other species still have not found growing. The best management practice used to manage weeds will depend upon the weed species present in the soil seed bank, and diversity of management tactics (e.g., planting dates) will result in fewer shifts in species composition

Early United States experience with liver donation after circulatory determination of death using thoraco‐abdominal normothermic regional perfusion: A multi‐institutional observational study

Mortality on the liver waitlist remains unacceptably high. Donation after circulatory determination of death (DCD) donors are considered marginal but are a potentially underutilized resource. Thoraco‐abdominal normothermic perfusion (TA‐NRP) in DCD donors might result in higher quality livers and offset waitlist mortality. We retrospectively reviewed outcomes of the first 13 livers transplanted from TA‐NRP donors in the US. Nine centers transplanted livers from eight organ procurement organizations. Median donor age was 25 years; median agonal phase was 13 minutes. Median recipient age was 60 years; median lab MELD score was 21. Three patients (23%) met early allograft dysfunction (EAD) criteria. Three received simultaneous liver‐kidney transplants; neither had EAD nor delayed renal allograft function. One recipient died 186 days post‐transplant from sepsis but had normal presepsis liver function. One patient developed a biliary anastomotic stricture, managed endoscopically; no recipient developed clinical evidence of ischemic cholangiopathy (IC). Twelve of 13 (92%) patients are alive with good liver function at 439 days median follow‐up; one patient has extrahepatic recurrent HCC. TA‐NRP DCD livers in these recipients all functioned well, particularly with respect to IC, and provide a valuable option to decrease deaths on the waiting list