Genetic diversity and structure of natural and agronomic switchgrass (Panicum virgatum L.) populations

Panicum virgatum L. (switchgrass) is an obligate outcrossing C₄ perennial prairie grass currently being pursued for the production of lignocellulosic ethanol. Commercial production of switchgrass for bioenergy has increased substantially in the United States. Understanding the degree of native genetic diversity within and among switchgrass populations will facilitate effective germplasm improvement, conservation, and management programs. In this study, the genetic diversity and differentiation among natural and agronomic switchgrass populations were analyzed at the molecular level by using random amplified polymorphic (RAPD) DNA markers. The mean genetic diversity among populations ranged from 0.051 ± 0.136 to 0.243 ± 0.214 and the mean genetic similarity among all the switchgrass populations was 0.775. The clustering pattern of switchgrass populations grouped the individuals based on their sites of origin, with agronomic cultivars predominantly separated into distinct clusters. The grouping of individuals within and across the populations was corroborated by principal component analysis. These results are consistent with previous reports for switchgrass accessions. RAPD DNA markers were suitable for quickly estimating the genetic diversity of native and agronomic switchgrass populations, and suggest that introgression of agronomic genes into natural switchgrass populations and subsequent changes in genetic structure may be detectable.     

Responses of three switchgrass (Panicum virgatum L.) cultivars to seed priming and differential aging conditions

Abstract

In switchgrass (Panicum virgatum L.) cultivation, rapid and uniform germination is essential because it is one of the most promising candidates for biofuel production. Priming, a seed enhancement technique with solid carriers, can be a useful tool for improving germination characteristics of switchgrass seeds. The objective of this study was to determine the effectiveness of priming on three non-aged and aged switchgrass cultivars of ‘Cave in rock’ ‘Dacotah’, and ‘Kanlow’. Seeds were primed with a synthetic calcium silicate (MicroCel E) and water at 30°C for five days. Seed, carrier and water proportions were 1 g, 0.5 g, and 1.5 mL, respectively. There was a 5% point (pp, Cave in rock), 8 pp (Dacotah), and 19 pp (Kanlow) increase in primed seeds compared with non-treated control seeds. Furthermore, priming decreased mean germination time by 26–36% in all seeds compared with the non-treated control. Accelerated aging was induced by storing seeds for 0, 10, and 21 days at 42°C and 95% relative humidity (RH). Germination percentage decreased and mean germination time increased with the aging. These results suggest that priming is an effective technique to improve the performance of switchgrass cultivars.     

Surveying Grassland Islands: the genetics and performance of Appalachian switchgrass (Panicum virgatum L.) collections

Genetic Resources and Crop Evolution - The interior Southeastern United States could contain novel germplasm for the bioenergy crop switchgrass due to its diverse habitats and geographic location...     

Movement,adsorption and mineralization of atrazine in two soils with and without switchgrass (Panicum virgatum) roots

A study was conducted to determine the influence of switchgrass roots on the mobility, adsorption–desorption and mineralization of atrazine in Cullen clay loam and Emporia loamy sand soils. Bromide and atrazine distribution profiles in the leachates indicated greater preferential movement in columns with roots than in columns without roots. Larger concentrations of atrazine were detected at lower depths of Emporia soil with switchgrass roots than without. Adsorption of atrazine was greater in Cullen than in Emporia soil and conformed to Freundlich isotherms. In both Cullen and Emporia soils, adsorption and desorption were not different between soil with or without switchgrass roots. After 84 days of incubation, less than 6% of the applied atrazine was mineralized in the Cullen soil and 2% in Emporia soil. Mineralization was greater in the Cullen soil than in the Emporia soil at 42, 56, 70 and 84 days of sampling. The presence of switchgrass roots did not affect the mineralization of atrazine in Emporia soil. The presence of switchgrass roots caused preferential movement of atrazine, but did not affect its adsorption and mineralization in either soil type.     

不同立地柳枝稷生长响应的初步研究

对黄土丘陵区不同立地中柳枝稷生长响应的变化规律进行了研究。结果表明:柳枝稷在不同立地条件下土壤水分明显不同,坡地土壤平均含水量(13.39%)<梯田(14.78%)<川地(16.02%)。土壤水分含量,根系生物量和土层深度三者存在密切相关性。在梯田、坡地和川地三种立地条件下,柳枝稷的株高、覆盖度、生物量、杂草和枯落物等均存在明显差异,其中柳枝稷的株高和覆盖度表现为川地>坡地>梯田;伴生杂草和柳枝稷枯落物与地上部生物量表现一致,川地显著高于坡地和梯田。地下生物量在川地、坡地和梯田立地下均呈现相同规律,随深度变化根系量逐渐减少,三种立地条件下总地下生物量差异不明显。同时发现土壤有机质和N含量与柳枝稷生产力呈显著正相关,说明了黄土丘陵区柳枝稷的生长响应与立地水肥条件有关。这对加强优良禾本科牧草的生态适应性研究及促进我国黄土高原生态可持续发展以及退耕还草工程具有重要的现实意义。     

Single-locus EST-SSR markers for characterization of population genetic diversity and structure across ploidy levels in switchgrass (<Emphasis Type="Italic">Panicum virgatum</Emphasis> L.)

Polyploidy, ploidal variation between populations, and aneuploidy within some populations complicate population genetic analyses in switchgrass. We report 21 genic-simple sequence repeat marker loci with single-locus disomic segregation in tetraploids and apparently tetrasomic inheritance in octoploids, thus allowing population genetic analyses across ploidy levels. Based on 472 individuals sampled over four tetraploid and eight octoploid cultivars, six to 55 alleles were detected per locus with an average of 24.1. Genetic diversity was greater in octoploids than tetraploids, as expected from polysomic inheritance. One tetraploid cultivar displayed comparable diversity to the least diverse octoploid cultivars, suggesting breeding history or population history in the native stands of origin may have also affected within-cultivar diversity. Amplicon number at each locus and population relationships suggest autopolyploid origin of octoploids within upland tetraploids with significant cultivar differentiation. However, model-based Bayesian clustering of individuals indicated that closely related octoploid cultivars are difficult to identify, possibly due to slowed differentiation by polysomic inheritance. The analysis of the sampling effect indicated addition of loci is more effective for cultivar identification than more individuals sampled per cultivar. Discriminating power of loci tended to correlate with their variability. The eight loci with greatest discriminatory power within tetraploids were equally successful as 20 loci at identifying the four tetraploid cultivars. The set of markers reported in this study are useful for characterization of switchgrass germplasm and identifying population structure for association studies.     

Differential resistance of switchgrass <Emphasis Type="Italic">Panicum virgatum</Emphasis> L. lines to fall armyworms <Emphasis Type="Italic">Spodoptera frugiperda</Emphasis> (J. E. Smith)

Six cultivars of switchgrass Panicum virgatum L., a plant native to North America that has potential as a bioenergy source, were evaluated for resistance to feeding by the fall armyworm Spodoptera frugiperda (J. E. Smith). Although no mortality was noted, seedlings of the cultivar ‘Trailblazer’ and older plants of the cultivar ‘Blackwell’ were among the most resistant to feeding by S. frugiperda. Some field-collected samples from natural habitat were fed upon by S. frugiperda as readily as were the cultivars, while others caused high mortality after 2 days. Enzyme assays indicated relative differences in expression of two peroxidases thought to be involved in insect resistance in maize, but not in two chitinolytic enzymes. Genomic searches based on maize-sequence templates for the aforementioned genes identified homologs in switchgrass. Sequencing of cDNA coding for these genes identified some differences, especially in the cationic peroxidase, which could influence relative activity. These results indicate switchgrass germplasm has varying resistance to fall armyworms which could be a function of gene sequence diversity, as well as of variation in gene expression due to differences in ploidy levels or other factors.     

不同施氮水平下紫花苜蓿与玉米间作对白浆土腐殖质组成的影响

以紫花苜蓿间作玉米(以下简称玉米间作)以及玉米单作3年定位试验的白浆土为研究对象,以玉米单作为对照,探索玉米间作在不同施氮水平下对白浆土腐殖质组成的影响。通过140、175、200和225 kg/hm~2 4个施氮水平的设置,探索了两种栽培模式在玉米拔节期、抽雄期和灌浆期对白浆土总有机碳(TOC)以及水溶性物质(WSS)、胡敏酸(HA)、可提取腐殖酸(HE)及胡敏素(Hu)组分碳含量(C_(WSS)、C_(HA)、C_(HE)和C_(Hu))的影响,并分析胡富比(C_(HA)/C_(FA))、HA碱溶液E_4/E_6的变化。结果表明:(1)无论玉米单作或是间作紫花苜蓿,配施200kg/hm~2氮均可在玉米灌浆期充分抑制TOC的矿化分解,使TOC含量为6.69和6.93 g/kg,显著高于其他处理;(2)玉米单作或是间作结合140 kg/hm~2施氮量均可显著提高玉米灌浆期的C_(Hu),在此施氮水平下,TOC中CHE比例也可得到显著提高;(3)玉米单作结合较高施氮水平(200和225 kg/hm~2)、玉米间作结合较低施氮水平(140和175kg/hm~2)均有利于FA向HA的转化,改善腐殖质品质,尤其在玉米抽雄期和灌浆期,玉米单作结合200 kg/hm~2施氮量能够较好促进HA形成,使C_(HA)达到1.85和1.74 g/kg,显著高于其他处理,在该施氮影响下,玉米间作紫花苜蓿更易促进HA分子的芳构化程度。     

Yield responses of cauliflower (Brassica oleracea L. var. Botrytis) to different water and nitrogen levels in a Mediterranean coastal area

Abstract

Global warming along with the increasing population and fresh water shortages necessitates a specific fertilization programme under water-scarce conditions. This study was conducted to investigate the effects of different irrigation and nitrogen levels on yield, growth components and water use characteristics of cauliflower (Brassica oleracea L. var. Botrytis cv. Tetris-F1) cultivated in a field for three consecutive years from 2005 to 2007 in the Eastern Mediterranean region of Turkey. Four irrigation (Kcp) levels with a drip irrigation system based on adjustment coefficients (0, 0.75, 1.0 and 1.25) of pan evaporation were used. Nitrogen (N) treatments were consisted of four different nitrogen rates (0, 75, 150 and 225 kg N ha^–1). The following yield and quality parameters were determined: curd weight, curd diameters, number of leaves per crop, above ground biomass (AGB) and curd/AGB ratio. Fertilizer use efficiency (FUE) and leaf mineral contents were also determined to clarify the productivity of N treatments. According to the results; the amount of irrigation water and/or total received water affects the plant water consumption, consequently, crop yield in a field grown cauliflower. The highest yield was obtained in Kcp1.0 irrigation level which represents full irrigation treatment. The excess water applications had negative effect on yield and AGB of cauliflower. Highest yield was obtained at 225 kg N ha^–1.

The water use efficiency and irrigation water use efficiency values increased with decreasing irrigation rate. However, lower Kcp coefficients resulted in lower total yield. The FUE in irrigation treatments showed linear increases from non irrigation to full irrigation plots. However, excessive irrigation caused a decrease in FUE. It can be recommended that the Kcp1.0 crop-pan coefficient with 225 kg ha^–1 nitrogen application can be used to achieve the highest yield for field grown cauliflower in the Eastern Mediterranean coastal region of Turkey.     

Volatile compounds and sensory attributes of wine from Cv. Merlot (Vitis vinifera L.) grown under differential levels of water deficit with or without a kaolin-based, foliar reflectant particle film

The volatile composition and sensory attributes of Merlot wines produced from vines under differing levels of water stress, with or without a foliar, kaolin-based particle film, were analyzed by stir bar sorptive extraction-gas chromatography-mass spectrometry (SBSE-GC-MS) and sensory evaluation. Vines were irrigated over consecutive vintages with 100, 70, or 35% of their estimated water requirements (ET(c)), or 35% until color change then 70% until harvest (35-70% ET(c)). Neither of the treatments consistently influenced ester concentrations or their relative amounts, though their concentrations varied from year to year. However, deficit irrigation had an effect on the concentration of terpene alcohols and norisoprenoids. Wines produced from vines under water deficit contained higher amounts of citronellol, nerol, geraniol, and β-damascenone, but linalool and β-ionone were not affected by deficit irrigation. Particle film did not affect volatile composition in the wine. Untrained panelists in 2007 and 2008 distinguished between wines from vines that received 100 or 35% ET(c) and between wines from vines that received 35 or 35-70% ET(c). Trained sensory panelists detected differences among wines for aroma, flavor, taste, and mouthfeel; however, significant interactive effects between particle film application and vine water status hindered interpretation of independent main effects.     

工厂化条件下氮处理对奶油生菜的生长及生理影响

通过水培试验研究不同氮处理(5 mmol·L~(-1)NO_3~--N、10 mmol·L~(-1)NO_3~--N和5 mmol·L~(-1)NO_3~--N+5 mmol·L~(-1)NH_4~+-N)对奶油生菜生长和生理特性的影响。研究结果表明,35 d后,总氮浓度相等时,NH_4~+-N抑制奶油生菜生长,该处理叶面积、株高、地上鲜重、地上干重、地下鲜重和地下干重分别降低78.2%、60.4%、87.0%、81.3%、80.1%和87.5%(P0.05),此外,两者的生理活性如根系活力、可溶性蛋白质、超氧化物歧化酶活性和硝酸还原酶活性均有显著性差异(P0.05)。与10 mmol·L~(-1)NO_3~--N(12.89 g)相比,5mmol·L~(-1)NO_3~--N(8.90 g)处理奶油生菜生物量稍微有所降低,叶面积、根长和地下干重分别降低48.1%、50.3%和37.5%(P0.05),而叶可溶性糖含量和花青素相对含量分别升高67.5%和51.9%(P0.05),而对NO_3~--N的吸收两者的比值在第21 d达到最大值,后者是前者的3.15倍。研究结果表明奶油生菜是喜硝蔬菜,且生菜的硝态氮适宜浓度前期(前21 d)为高浓度(10 mmol·L~(-1)),以便促进奶油生菜生长,后期(21 d后)可改为低浓度(5 mmol·L~(-1))以提高品质。     

一个水稻鞘叶特异表达启动子的克隆及功能鉴定

目前在基因工程中应用最广的为组成型启动子,但是组成型启动子驱动外源基因在各组织中持续恒定的表达可能引起植物发育迟缓等问题,因此克隆来源于作物本身的组织特异型启动子逐渐受到重视。根据本实验室基因芯片数据库找到一个在水稻绿色组织特异表达的基因(TIGR Locus:LOC_Os06g21110),用 PCR 技术从水稻明恢 63(Oryza sativa L ssp. indica)基因组中克隆得到其上游启动子命名为GSP (green-tissue specific promoter),长度为1 951 bp。将GSP与带有β-glucuronidas(gus)报告基因的的植物表达载体连接,经农杆菌(Agrobacterium)介导转化水稻中花11 (O. sativa L ssp. japonica)成熟种子胚诱导的愈伤组织,获得转基因水稻阳性植株,通过组织化学染色法证明,GSP是一个叶鞘和叶片特异表达启动子。对其进行5’端缺失分析,构建了7个缺失载体,通过验证缺失载体的表达谱,证明592 bp长度的启动子就足以维持鞘叶特异表达模式,初步鉴定出了该启动子的核心功能区域。本研究所克隆出的GSP 启动子是一个未曾报道过的鞘叶特异表达启动子,基因工程中利用此类启动子可以在改良水稻性状的同时减少对水稻生理方面的副作用,有良好的应用价值。     

Greenhouse gas emissions from a wastewater sludge-amended soil cultivated with wheat (Triticum spp. L.) as affected by different application rates of charcoal

Applying biochar to soil is an easy way to sequester carbon in soil, while it might reduce greenhouse gas (GHG) emissions and stimulate plant growth. The effect of charcoal application (0, 1.5, 3.0 and 4.5%) on GHG emission was studied in a wastewater sludge-amended arable soil (Typic Fragiudepts) cultivated with wheat (Triticum spp. L.) in a greenhouse. The application of charcoal at ≥1.5% reduced the CO₂ emission rate significantly ≥37% compared to unamended soil (135.3 g CO₂ ha⁻¹ day⁻¹) in the first two weeks, while the N₂O emission rate decreased 44% when 4.5% charcoal was added (0.72 g N₂O ha⁻¹ day⁻¹). The cumulative GHG emission over 45 days was 2% lower when 1.5% charcoal, 34% lower when 3.0% charcoal and 39% lower when 4.5% charcoal was applied to the sludge-amended soil cultivated with wheat. Wheat growth was inhibited in the charcoal-amended soil compared to the unamended soil, but not yields after 135 days. It was found that charcoal addition reduced the emissions of N₂O and CO₂, and the cumulative GHG emissions over 45 days, without altering wheat yield.     

An assessment of the genetic diversity within a collection of<Emphasis Type="Italic">Saccharum spontaneum</Emphasis> L. with RAPD-PCR

A local collection of 33Saccharum spontaneum L. clones and two sugarcane cultivars (LCP 82-89 and LCP 85-384) were assessed for genetic variability using random amplified polymorphic DNA (RAPD)-PCR. A total of 157 polymorphic RAPD-PCR bands were scored with 17 primers. The number of RAPD-PCR products per primer ranged from four to 16. The data were analyzed with two multivariate analysis software programs, NTSYSpc and DNAMAN®. Although these two programs yielded similar results, a bootstrapped phylogenetic tree could only be generated with the DNAMAN® software. A substantial degree of genetic diversity was found within the localS. spontaneum collection. Pairwise genetic homology coefficients ranged from 65% (SES, 196/Tainan 2n = 96) to 88.5% (IND 81-80/IND 81-144). LCP 82-89 and LCP 85-384 shared a greater similarity (82%) than either was to any clone ofS. spontaneum (ranging from 60.5 to 75.2%). The 33S. spontaneum clones were assigned to eight groups independent of their geographic origin or morphology, while the two sugarcane cultivars were assigned to the ninth group. All but two pairs ofS. spontaneum clones could be distinguished by a single RAPD primer OPBB-02. The use of a second primer, either OPBE-04 or Primer 262, separated allS. spontaneum clones. One amplification product from the RAPD primer OPA-11, OPA-11-336, proved to be cultivar-specific and has been adopted for use in our breeding program. Information from this study would help conserve the genetic diversity ofS. spontaneum. Disclaimer: Product names and trademarks are mentioned to report on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by USDA does not imply the approval of the product to the exclusion of others that may also be suitable. The experiments reported comply with the current laws of the USA.     

The genetic diversity associated with seed proteins in a collection of Spanish underground vetches (<Emphasis Type="Italic">Vicia sativa</Emphasis> L. subsp. <Emphasis Type="Italic">amphicarpa</Emphasis> (Dorthes) Asch. et Graebn.)

The characterization of plant genetic resources is the first step towards improving their use. The Spanish Plant Genetic Resources Centre, which belongs to the National Institute for Agricultural and Food Technology Research (CRF-INIA), conserves accessions of wild underground vetches collected in Spain. In the present work, 26 underground vetch accessions were characterized in terms of their seed storage proteins (separated by SDS-PAGE) as a means of assessing the genetic variation of these plants and their agronomic value. Vicia sativa cv. Vereda was used as control. A total of 54 bands were detected, of which 49 were polymorphic. Fifty eight different electrophoretic patterns were observed in total. Protein bands were scored in terms of their presence (1) or absence (0) for all the seeds studied, and two matrices constructed, one with all the bands present in each accession, the other with the different patterns for each accession. Dendrograms based on the Jaccard similarity index and the UPGMA clustering method were produced from these matrices, and the degree of genetic variation between and within accessions was calculated. The groups obtained were compared with the chromosome number for each accession. The results reflect the great diversity of underground vetch seed storage proteins. The aerial and underground seeds of 16 accessions were then analysed separately. In some cases, the aerial and underground flowers of the same plant produced different proteins.     

Assessing the influence of technosol and biochar amendments combined with <Emphasis Type="Italic">Brassica juncea</Emphasis> L. on the fractionation of Cu,Ni, Pb and Zn in a polluted mine soil

Purpose

Soil metal pollution is a widespread problem around the world and remediation of these soils is difficult. The objective of this study was to investigate the effect of two different strategies on the chemical fractions of metals in a soil of a depleted copper mine: (1) amending with a mixture of a technosol made of wastes and biochar and (2) amending combined with planting vegetation (Brassica juncea).

Materials and methods

A 3-month greenhouse experiment was carried out to evaluate the effects of organic amendments and vegetation on the metal fractionation of Cu, Ni, Pb and Zn in a mine soil of the depleted copper mine at Touro (Spain). We compared the influence of organic amendments alone (technosol?+?biochar) and combined with mustard plants (Brassica juncea L.).

Results and discussion

The results showed that amending with a technosol made of wastes promoted plant growth (from 0.7 to 2.9 g of biomass produced) and reduced the CaCl₂-extractable metal concentration in soil, reduced the mobility factor of Cu from 18.3 to 1.6, Ni from 47.5 to 2.3 and Pb from 17.9 to 2.1, and also reduced the concentration of metals in the mobile soil fractions. It was not possible to grow up Brassica juncea plants in the untreated settling pond soil due to the extremely degraded conditions of that soil. However, the application of the used technosol increased the Pb and Zn pseudototal concentrations in the amended soils.

Conclusions

We conclude that the combination of amending with wastes and planting B. juncea provides little additional benefit for remediating a metal-polluted soil compared with incorporation of wastes alone.