高羊茅FaChit1基因启动子的功能分析

用含有不同长度FaChitl基因启动子区域与GUS基因融合构建植物表达载体pFaChitlP—I、pFaChitlP-Ⅱ以及pFaChitlP-Ⅲ并分别对烟草进行转化,经真菌激发子、干旱、机械损伤以及乙烯等多种胁迫处理后测定GUS活性。启动子缺失分析实验结果显示,真菌激发子对FaChitl基因启动子所介导的GUS诱导表达效果最强,而机械损伤只能微弱地诱导GL靥基因表达;FaChitl基因启动子-651bp以内的序列均能介导GUS基因的诱导表达,同时-935bp与-233bp之间的区域是该启动子响应真菌激发子、乙烯以及机械损伤胁迫所必需的。表明FaChitl启动子是一个多胁迫诱导型启动子。     

Relationship between soluble carbohydrate level and tolerance of meadow fescue callus to Bipolaris sorokiniana (Sacc.) Shoem. and Drechslera dictyoides (Drechsl.) Shoem. metabolites

The aim of the presented work was the search for the relationship between the level of soluble carbohydrates in callus tissues of eight meadow fescue (Festuca pratensis Huds.) cultivars and their growth ability on media containing Bipolaris sorokiniana and Drechslera dictyoides metabolites. Calli were induced from mature grains using the method previously described (Płażek 1994). Callus obtained from single caryopsis was cut into three pieces which were weighted and put on the media with or without pathogen metabolites. Tissue selection was performed by means of “double-layer culture” technique (Lepoivre et al. 1986). After two-week culture in the darkness at temp. of 25°C the calli were weighted again. The sugar level in tissue was measured by means of colorimetric method of Klein & Weissman according to Snell (1961). Fresh mass decrease of calli developing on the media with fungus metabolites was observed by all studied object. The tolerance of calli of the tested cultivars to metabolites of both pathogens was significantly different. However, significant similarity between the tolerance of calli of particular varietes to both fungi was noted. The soluble carbohydrate contents in control tissue of all studied cultivars were similar and their values ranged between 2.4 and 3 % of fresh mass. B. sorokiniana metabolites caused a significant decrease of the sugar content in calli, while D. dictyoides metabolites did not decrease the sugar level.     

Spatial models of pollen dispersal in the forage grass meadow fescue

Several bivariate probability distributions, generated by different underlying dispersal mechanisms, are fitted to the observed frequencies of an isozyme marker gene using a maximum likelihood approach. The pollen dispersal data were generated using two experimental populations of meadow fescue (Festuca pratensis Huds.), homozygous for different allozymes at the (Pgi-2) locus, arranged in a circular donor–acceptor field design. The contribution of a plant depends on plant position, fecundity and flowering time, factors which are taken into account when fitting the different models. Several approximate likelihood-ratio tests are done between alternative nested models, and a wind threshold model with bimodality in the wind direction is selected. The evolutionarily important variances and expectations of gene displacement under the selected model are calculated. It is also shown that the underlying probability distribution is significantly more than exponentially leptokurtic. By fitting a distribution of deposition in all three dimensions to the data, taking into account differences in plant height, separate estimates of additional physical parameters are obtained, showing that gravity and vertical random movements are more important than intervening vegetation in limiting pollen dispersal in meadow fescue. According to the model, plants with a high seed yield contribute pollen over-proportionally to neighbouring plants. This revised version was published online in July 2006 with corrections to the Cover Date.     

Distribution of15N in the soil-plant system during a four-year field lysimeter study with barley (Hordeum distichum L.) and perennial meadow fescue (Festuca pratensis Huds.)

An annual cereal, barley, and a perennial grass ley, meadow fescue, were grown in field lysimeters in Sweden and fertilized with 12 and 20g Ca(NO₃)₂-N m⁻² yr⁻¹, respectively. Isotope-labeled (¹⁵N) fertilizer was added during year 1 of the study, whereafter similar amounts of unlabeled N were added during years 2 and 3. The grass ley lysimeters were ploughed after the growing season of year 3 and sown with barley during year 4. The barley harvest in year 1 removed 59% of the added fertilizer N, while the fertilizer N export by two meadow fescue harvests in year 1 was 65%. The labeled N export decreased rapidly after year 1, especially in the barley, but increased slightly after ploughing of the grass ley. The microbial biomass, measured with the chloroform fumigation method, incorporated a maximum of 1.4–1.7% of the labeled N during the first seven weeks after application. Later on, the incorporation stabilized at less than 1% in both cropping systems. The susceptibility of the residual labeled N to mineralization was evaluated three years after application by means of long-term laboratory incubations. The curves of cumulative mineralized N were described by a two-component first-order regression model that differentiated between an available and a more recalcitrant fraction of potentially mineralizable N. There was no difference in the amounts of potentially mineralizable N between the cropping systems. The labeled N comprised 5 and 2% of the amounts of potentially mineralizable N in the available and more recalcitrant fraction, respectively. The mineralization rate constants for the labeled N were almost twice as high as for the total potentially mineralizable N. The available fraction of the total potentially mineralizable N was 12%, while twice that proportion of the labeled N was available. It was concluded that the short-term ley did not differ from the annual crop with respect to the early disposition of the fertilizer N and the behaviour of the residual organic N.     

Influence of conservation reserve program mid-contract management and landscape composition on northern bobwhite in tall fescue monocultures

The United States Department of Agriculture (USDA) authorized mid-contract management (MCM) in 2004 to restore and maintain plant species composition and structural diversity in aging Conservation Reserve Program (CRP) fields for the northern bobwhite (Colinus virginianus) and other grassland-dependent wildlife. We implemented 3 USDA-approved MCM regimes (i.e., strip disking, strip glyphosate spraying, and strip glyphosate spraying in combination with legume interseeding) in 60 tall fescue (Festuca arundinaceae) CRP monocultures in south-central Illinois, USA, during 2005–2008. We hypothesized that adult bobwhite relative densities and brood presence would increase following MCM that effectively restored early successional plant communities in otherwise monotypic stands of tall fescue. We estimated annual adult bobwhite relative densities and brood presence-absence in managed and unmanaged CRP. We modeled vegetation characteristics and landscape composition to identify factors influencing adult densities and brood presence. Adult relative densities were 2-fold greater in managed fields than in unmanaged fields, and were negatively correlated with greater percentages of grass cover. Adult densities were positively correlated with greater plant species diversity, and greater percentages of bare ground and legume cover. Logistic regression and odds ratio estimates indicated that fields managed with glyphosate-interseed and glyphosate treatments were 39.6% more likely to have broods than unmanaged CRP, whereas disked fields were 10.0% more likely than unmanaged CRP. These models indicated that the probability of brood presence was greater in fields with increased percentage of bare ground, greater plant species diversity, and decreased percentage of grass and litter cover. These findings suggest that a 3-year rotation of glyphosate or glyphosate-interseed treatments can enhance habitat conditions for adult bobwhites and broods in CRP tall fescue monocultures. © 2011 The Wildlife Society.     

Acute exposure to ergot alkaloids from endophyte-infected tall fescue does not alter absorptive or barrier function of the isolated bovine ruminal epithelium

Ergot alkaloids in endophyte-infected (Neotyphodium coenophialum) tall fescue (Lolium arundinaceum) have been shown to cause a reduction in blood flow to the rumen epithelium as well as a decrease in volatile fatty acids (VFA) absorption from the washed rumen of steers. Previous data also indicates that incubating an extract of endophyte-infected tall fescue seed causes an increase in the amount of VFA absorbed per unit of blood flow, which could result from an alteration in the absorptive or barrier function of the rumen epithelium. An experiment was conducted to determine the acute effects of an endophyte-infected tall fescue seed extract (EXT) on total, passive or facilitated acetate and butyrate flux across the isolated bovine rumen as well as the barrier function measured by inulin flux and tissue conductance (G_t). Flux of ergovaline across the rumen epithelium was also evaluated. Rumen tissue from the caudal dorsal sac of Holstein steers (n=6), fed a common diet, was collected and isolated shortly after slaughter and mounted between two halves of Ussing chambers. In vitro treatments included vehicle control (80% methanol, 0.5% of total volume), Low EXT (50 ng ergovaline/ml) and High EXT (250 ng ergovaline/ml). Results indicate that there is no effect of acute exposure to ergot alkaloids on total, passive or facilitated flux of acetate or butyrate across the isolate bovine rumen epithelium (P>0.51). Inulin flux (P=0.16) and G_t (P>0.17) were not affected by EXT treatment, indicating no alteration in barrier function due to acute ergot alkaloid exposure. Ergovaline was detected in the serosal buffer of the High EXT treatment indicating that the flux rate is ~0.25 to 0.44 ng/cm² per hour. Data indicate that specific pathways for VFA absorption and barrier function of the rumen epithelium are not affected by acute exposure to ergot alkaloids from tall fescue at the concentrations tested. Ergovaline has the potential to be absorbed from the rumen of cattle that could contribute to reduced blood flow and motility and lead to reduced growth rates of cattle.     

越冬期间高羊茅叶片和根颈的抗冻性与碳水化合物和脯氨酸含量的关系

随着冬季气温的降低,高羊茅叶片、根颈中可溶性糖类和脯氨酸含量逐渐上升,抗冻性逐渐增强;春季气温逐渐回升时,两者含量则缓慢地减少,抗冻性逐渐减弱.半致死温度(LT50)与总可溶性糖、脯氨酸含量之间呈极显著负相关.     

Vigor and salt tolerance in 3 lines of tall wheatgrass

The F₁ progeny of the cross of two salt-tolerant lines of Thinopyrum elongatum [Host] D. R. Dewey grew better than either parent under non-saline and saline growth conditions. Under non-saline conditions, the hybrid produced 1.8 times as much vegetative tissue as one parent and 3.2 times more than the other parent in the same length of time. The relative growth rates of the 2 parental lines decreased equally as media osmotic potentials decreased. The relative growth rate of the hybrid did not decrease as rapidly as that of the parents; therefore, it was concluded that the greater growth of the hybrid was due to increased salt tolerance. Carbohydrate reserves and water-soluble solutes believed to be involved in osmotic adjustment were assayed to determine if there were any differences between the hybrid and its parents in their abilities to accumulate these compounds. The concentrations of these constituents were measured at dawn and at dusk of the same day in plants grown in media at osmotic potentials ranging from –0.1 to –1.2 MPa. There were no differences in pool sizes of the organic compounds in the 3 lines. Starch increased 10–40 fold in leaves from dawn to dusk and sucrose increased 100-fold. However, this pattern was unaffected by salinity. Conversely, betaine concentrations increased with increasing salinity but were the same at dawn and dusk. Na⁺ and K⁺ were affected by both light and salinity. Cl was one-half (Na⁺+ K⁺) on a molar basis under all conditions. Proline accumulated when (Na⁺+ K⁺) exceeded 200 μmol (g fresh weight)^?1. Since this amount of (Na⁺+ K⁺) existed only in tissues harvested at dusk from severely saline-stressed plants, only leaves from such plants harvested at dusk contained proline.     

Phylogeographical history of the widespread meadow fescue (Festuca pratensis Huds.) inferred from chloroplast DNA sequences

Aim Here we explore the variation in chloroplast DNA (cpDNA) in a widespread Eurasian diploid forage grass, meadow fescue (Festuca pratensis Huds.), to address its phylogeographical history. In particular, we aim to answer whether the post‐glacial migration routes of meadow fescue are associated with the spread of agriculture or concurrent with well‐documented natural migration pathways from glacial refugia. Location A total of 56 Eurasian accessions of F. pratensis were analysed, representing the entire native distribution area as well as non‐native areas in northernmost Europe. Methods Based on initial sequencing of 10 non‐coding cpDNA regions, three regions were sequenced for all F. pratensis accessions. For reference, three closely related species [the diploid Lolium perenne L. and the polyploids Festuca arundinacea Schreb. and Festuca gigantea (L.) Vill.] were also sequenced, as well as the more distantly related Festuca ovina L. Divergence times were estimated assuming a simple molecular clock, calibrated using a previously published estimate of 9 Myr for the divergence between fine‐leaved (F. ovina) and broad‐leaved fescues (F. pratensis, F. arundinacea and F. gigantea). Results Limited, but geographically structured, cpDNA variation was observed in F. pratensis. Three haplotypes, estimated to have diverged 0.16 Ma, were identified: one western European (A), one with a wide eastern distribution from central‐eastern Europe into Asia (B) and one Caucasian (C). The haplotypes of the polyploids and L. perenne were estimated to have diverged from haplotype A in F. pratensis 0.8–1.3 Ma. Main conclusions We found no definite evidence for migration of the diploid F. pratensis associated with the spread of agriculture from the Fertile Crescent after the last glaciation. The distinct geographical structuring of the present‐day variation in cpDNA can rather be explained by northwards expansion of the western haplotype from an Iberian refugium, expansion of the eastern haplotype from an unlocated (south‐)eastern refugium and glacial survival without subsequent expansion from a Caucasian refugium. The high level of cpDNA divergence observed between this diploid and the polyploids which have probably been derived from it may suggest that the very low level of cpDNA variation in the diploid is caused by a recent bottleneck. Today, F. pratensis is widespread in the open agricultural landscape but appears otherwise confined to naturally open habitats such as river banks, and its populations may have been decimated when dense forests dominated in the previous interglacial.     

Host Status of Endophyte-Infected and Noninfected Tall Fescue Grass to Meloidogyne spp

Tall fescue grass cultivars with or without endophytes were evaluated for their susceptibility to Meloidogyne incognita in the greenhouse. Tall fescue cultivars evaluated included, i) wild-type Jesup (E+, ergot-producing endophyte present), ii) endophyte-free Jesup (E-, no endophyte present), iii) Jesup (Max-Q, non-ergot producing endophyte) and iv) Georgia 5 (E+). Peach was included as the control. Peach supported greater (P ≤ 0.05) reproduction of M. incognita than all tall fescue cultivars. Differences in reproduction were not detected among the tall fescue cultivars and all cultivars were rated as either poor or nonhosts for M. incognita. Suppression of M. incognita reproduction was not influenced by endophyte status. In two other greenhouse experiments, host susceptibility of tall fescue grasses to two M. incognita isolates (BY-peach isolate and GA-peach isolate) did not appear to be related to fungal endophyte strain [i.e., Jesup (Max-Q; nontoxic endophyte strain) vs. Bulldog 51 (toxic endophyte strain)]. Host status of tall fescue varied with species of root-knot nematode. Jesup (Max-Q) was rated as a nonhost for M. incognita (BY-peach isolate and GA-peach isolate) and M. hapla, a poor host for M. javanica and a good host for M. arenaria. Bulldog 51 tall fescue was also a good host for M. arenaria and M. javanica, but not M. incognita. Jesup (Max-Q) tall fescue may have potential as a preplant control strategy for M. incognita and M. hapla in southeastern and northeastern United States, respectively.