Main conclusion : According to the results presented in this paper the fungal endophyte Epichloee typhina significantly improves the growth, PSII photochemistry and C assimilation efficiency of its ...host Dactylis glomerata. In this paper, we present a comprehensive study of the impact of the endophytic fungi Epichloee typhina on its plant hosts' photosynthesis apparatus. Chlorophyll a fluorescence, gas exchange, immuno-blotting and spectrophotometric measurements were employed to assess photosynthetic performance, changes in pigment content and mechanisms associated with light harvesting, carbon assimilation and energy distribution in Dactylis glomerata colonized with Epichloee typhina. According to the results presented in this study, colonization of D. glomerata results in improved photosynthesis efficiency. Additionally, we propose a new mechanism allowing plants to cope with the withdrawal of a significant fraction of its energy resources by the endophytic fungi. The abundance of LHCI, LHCII proteins as well as chlorophyll b was significantly higher in E+ plants. Malate export out of the chloroplast was shown to be increased in colonized plants. To our knowledge, we are the first to report this phenomenon. Epichloee colonization improved PSII photochemistry and C assimilation efficiency. Elevated energy demands of E+ D. glomerata plants are met by increasing the rate of carbon assimilation and PSII photochemistry.
Drought is one of the most important abiotic stresses limiting plant survival, growth, and production in many regions of the world. Approximately one-thirds of the world's agricultural lands are in ...arid and semi-arid regions, including Iran. Therefore, there is a need to improve plant cultivars with high adaptability and low water requirement. This study was conducted to evaluate the drought tolerance of Bromus inermis and Dactylis glomerata genotypes and investigate the relationship between seed yield and forage yield to select better genotypes in terms of these traits, simultaneously. In this study, 36 genotypes selected from polycross populations of both species were clonally propagated and evaluated under normal and drought-stressed conditions during 2014 and 2015 at the Research Farm of Isfahan University of Technology, Isfahan, Iran. In both species, high genetic variation was observed among genotypes for seed yield and its components indicating high potential for improving these traits through targeted selection in breeding programs. Drought stress negatively affected seed yield and its components and reduced the genetic diversity of most traits. Most of the studied traits had relatively high heritability; therefore, improvement of these traits is possible through recurrent selection in breeding programs. The significant association between seed and forage yield indicated that it is possible to select superior genotypes based on seed and forage yield in both normal and water stress conditions, simultaneously. However, the intensity of this association was higher in Dactylis glomerata than Bromus inermis. In both species and under both normal and drought stress conditions, better genotypes were identified in terms of seed and forage yield. These genotypes can be used in developing genetic populations for simultaneous improvement of seed and forage yield in future studies and also for the development of synthetic varieties in both species.
Sequence-related amplified polymorphism (SRAP) and inter-simple sequence repeat (ISSR), two advanced molecular markers for genetic research in grass and forage, were used to analyze the genetic ...diversity among 44 accessions of cocksfoot collected from seven countries and regions. 21 SRAP primer combinations generated 476 bands, of which 401 were polymorphic (84.24%). Using 12 ISSR primers, 100 polymorphic bands out of 115 bands in total were generated (86.96%). The coefficient of genetic similarity from SRAP and ISSR data ranged from 0.6838 to 0.9686 and from 0.6935 to 0.9231, respectively. Based on unweighted pair group method with arithmetic mean (UPGMA) cluster and principal component analysis (PCA) on a series of genetic characteristics, all accessions were divided into three clusters and four clusters using two markers, respectively. Those, accessions collected from the identical continent were classified into the same cluster, suggesting the geographical distribution of genetic diversity of cocksfoot. The genetic diversity of Chinese cocksfoot except for three Chinese cultivars was rather rich and greater than that of other regions. We proposed that both SRAP and ISSR markers were considered as useful tools for evaluating the genetic diversity of cocksfoot. Especially, SRAP detected more variance and gave clearer cluster groups.
The carried-out experiment aimed to assess the influence of ash derived from the thermochemical conversion of feathers (AGF) as a soil amendment, and Dactylis glomerata L. as a test plant in aided ...phytostabilization of soil strongly contaminated by Cu, Cd, Pb and Zn. The influence of AHG on the chemical properties of soil (pH as well as total and CaCl2-extracted heavy metals) as well as the plant yield and concentration of heavy metals in the roots and shoots. The applied soil amendment influenced an increase in the pH values of soil (by 0.4 units) and a reduction in CaCl2-extractable forms of Zn (25%), Cu (23%), Cd (20%) and Pb (12%), as well as total forms of Cu (35%), Zn (35%), Pb (20%) and Cd (17%) in the soil. The plant yield of the shoots of Dactylis glomerata L. following the application of AGF was 31% higher when compared to the control series. The roots of the tested plant in the AGF series contained higher values of the analyzed heavy metals in relation to the shoots, which was especially visible in the case of Pb (more than twice as high) and Cd (37%).
Carbon sequestration is an important means of reducing the concentration of atmospheric CO sub(2) by injecting CO sub(2) into subterranean geological reservoirs known as sequestration fields. These ...deep sequestration fields must be monitored for structural integrity to ensure their long-term efficacy. Stress responses of plants to super-elevated soil CO sub(2) are signatures that we evaluated as potential tools for surface leak detection of CO sub(2) at the Zero Emission Research and Technology (ZERT) site in Bozeman, MT. To mimic a compromised field, CO sub(2) was deliberately released at a rate of 0.15 ton/day through a 100 m long and 2.0-2.3 m deep Horizontal Injection Well (HIW) with intentional leaks, with injections of CO sub(2) taking place on these dates: 7/19-8/15/2010 and 7/18-8/15/2011. Periodically over two years, we measured stomatal conductance, chlorophyll content, and specific leaf area in Taraxacum officinale Wigg. (dandelion) and Dactylis glomerata L. (orchard grass) along a 20 m transect perpendicular to a hot spot. Hot spots were visible as circular zones of leaf dieback where T. officinale leaves turned from green to red and became brown and desiccated. CO sub(2) concentrations reached 29% by volume at the edges of hot spots. During CO sub(2) injection, chlorophyll content (as measured with a Hansatech CL-O1 chlorophyll content meter to obtain a unitless measure) decreased significantly (p < 0.001) in T. officinale from 9.486 to 1.912 (80%) in 2010 and from 8.288 to 0.000 (99%) in 2011. The less pronounced decreases in chlorophyll content with CO sub(2) injection in D. glomerata were 34% in 2010 and 37% in 2011. Average stomatal conductance (g sub(s)) rates in T. officinale were highest at the hot spot (22.41 mmol m super(-2) s super(-1) in 2010, 46.10 mmol m super(-2) s super(-1) in 2011) and lowest 20 m distally (11.76 mmol m super(-2) s super(-1) in 2010 and 3.69 mmol m super(-2) s super(-1) in 2011). Average g sub(s) rates in D. glomerata were highest at the hot spot (53.91 mmol m super(-2) s super(-1) in 2010 and 65.96 mmol m super(-2) s super(-1) in 2011), and lowest 20 m distally (38.52 mmol m super(-2) s super(-1) in 2010 and 24.83 mmol m super(-2) s super(-1) in 2011). These results suggest T. officinale leaves are more sensitive to super-elevated soil CO sub(2) concentration than D. glomerata leaves and generally, that species-specific physiological responses of these leaves to varying concentrations of soil CO sub(2) may be useful in monitoring CO sub(2) leakage in vegetated areas above CO sub(2) storage sites.
Orchardgrass (Dactylis glomerata L.) is a long‐lived, cool‐season forage grass that is commonly used for hay production. Despite its economic importance, orchardgrass genome remains relatively ...unexplored. In this study, we used Illumina RNA sequencing to identify gene‐associated molecular markers, including simple sequence repeats (SSRs) and single nucleotide polymorphisms (SNPs), as well as heat stress‐induced differentially expressed genes (DEGs) in two orchardgrass genotypes, ‘Baoxing’ (heat resistant) and ‘01998’ (heat susceptible). Approximately 163 million high‐quality trimmed reads were generated from 207 million raw reads using the Illumina HiSeq 2000 platform. A total of 126 846 unigenes were obtained after de novo assembly of the trimmed reads, and 40 078 unigenes were identified as coding sequences (CDSs). Based on the assembled unigenes, 669 300 high‐quality SNPs, including 416 099 transitions and 257 736 transversions, were contained in 75 875 unigenes. In addition, a total of 8475 microsatellites were detected in 7764 unigenes. When placed under heat stress, the total number of DEGs in ‘Baoxing’ (3527) was higher than in ‘01998’ (2649), indicating that in comparison with heat‐susceptible ‘01998’, heat‐resistant ‘Baoxing’ seems to have more unigenes that respond to heat stress. The high‐throughput transcriptome sequencing of orchardgrass under heat stress provides useful information for gene identification and for the development of SNP and SSR molecular markers. The comparison of DEGs under different periods of heat stress allowed us to identify a wealth of candidate DEGs that can be further analysed in order to determine the genetic mechanisms underlying heat tolerance in orchardgrass.
Summary
Orchardgrass (Dactylis glomerata L.) is an important forage grass for cultivating livestock worldwide. Here, we report an ~1.84‐Gb chromosome‐scale diploid genome assembly of orchardgrass, ...with a contig N50 of 0.93 Mb, a scaffold N50 of 6.08 Mb and a super‐scaffold N50 of 252.52 Mb, which is the first chromosome‐scale assembled genome of a cool‐season forage grass. The genome includes 40 088 protein‐coding genes, and 69% of the assembled sequences are transposable elements, with long terminal repeats (LTRs) being the most abundant. The LTRretrotransposons may have been activated and expanded in the grass genome in response to environmental changes during the Pleistocene between 0 and 1 million years ago. Phylogenetic analysis reveals that orchardgrass diverged after rice but before three Triticeae species, and evolutionarily conserved chromosomes were detected by analysing ancient chromosome rearrangements in these grass species. We also resequenced the whole genome of 76 orchardgrass accessions and found that germplasm from Northern Europe and East Asia clustered together, likely due to the exchange of plants along the ‘Silk Road’ or other ancient trade routes connecting the East and West. Last, a combined transcriptome, quantitative genetic and bulk segregant analysis provided insights into the genetic network regulating flowering time in orchardgrass and revealed four main candidate genes controlling this trait. This chromosome‐scale genome and the online database of orchardgrass developed here will facilitate the discovery of genes controlling agronomically important traits, stimulate genetic improvement of and functional genetic research on orchardgrass and provide comparative genetic resources for other forage grasses.
Heavy metal contaminations in the environment of mining area have become a global problem. The vicinity of an iron ore mine was investigated to estimate the concentrations of As, Pb, Cd, Mn, Ni, Zn, ...and Cr in the soil and the feasibility of using native plants for phytoremediation. For this, concentrations of elements in soil samples collected and were analyzed by inductivity coupled plasma optical emission spectrometry. The concentrations of heavy metals and arsenic in the roots and aerial parts of Dactylis glomerata L. and Scleranthus orientalis Rössler were analyzed by inductively coupled plasma mass spectrometer too. As concentrations in the samples surpassed the soil toxicity threshold. Cd concentration in soil samples was considerably high next to mine pit. Neither species was identified as a hyperaccumulator, but both species could be considered as excluder plants for As.
Pastures that include annual and perennial grasses can play a strategic role in increasing the sustainability of temperate livestock systems. However, the impacts of the competition between annual ...and perennial genetically improved forage species on pastures has scarcely been studied. We evaluated the early dynamics of tillering, carbon partitioning and both intra- and interspecific competition in – or between – an annual (Bromus willdenowii; prairie grass; Bw) and a perennial (Dactylis glomerata; orchard grass; Dg) C3 grass species. We sowed 24 0.18 m2 microplots in May 2008. Each microplot constituted an experimental unit and contained five sowing lines spaced 0.175 m apart. On three of the lines, we sowed different combinations of the mentioned grasses, while on the two lines between them, we sowed red clover (Trifolium pratense). We randomly applied a factorial array of eight treatments—2 species (Dg vs. Bw) × 2 types of competition (intra vs. interspecific) × 2 levels of winter nitrogen fertilization (0 vs. 170 kg of N ha-1)—designed in three complete random blocks. Fertilization did not have any significant effect on any species. The evaluation period lasted 109 days after sowing (das), separated into three phases (0-53 das, 59-90 das and 90-109 das). The variables recorded were aerial biomass (leaves, sheets and senescent material), root biomass and tiller density per species. As expected, annual Bw inhibited the growth of perennial Dg at the latest stage of establishment but surprisingly promoted it at the earliest stage. This work suggested that a low initial density of an annual species should optimize the initial facilitating effect of the annual species on the perennial species with its subsequent inhibitory effect.
PDF
