Viridepyronone, a new antifungal 6-substituted 2H-pyran-2-one produced by Trichoderma viride

A new antifungal 6-substituted 2H-pyran-2-one, named viridepyronone, has been isolated from a cultural filtrate of a strain of Trichoderma viride showing antagonistic activity in vitro toward Sclerotium rolfsii, which is the causal agent of crown and stem rot of artichoke. Viridepyronone was characterized as 6-(4-oxopentyl)-2H-pyran-2-one 2 with spectroscopic methods. Bioassays showed that viridepyronone had a good antifungal activity against S. rolfsii, and its minimum inhibitory concentration (over 90% inhibition) was found to be 196 microg/mL. This is the first report of viridepyronone produced by any species of fungi.     

Antifungal activity of 4-methyl-6-alkyl-2H-pyran-2-ones

A number of 4-methyl-6-alkyl-alpha-pyrones were synthesized and characterized on the basis of 1H NMR and mass spectroscopy. These compounds were tested in vitro against pathogenic fungi, namely, Sclerotium rolfsii Saccardo, Rhizoctonia bataticola (Taub.) Butler, Pythium aphanidermatum (Edson) Fitz., Macrophomina phaseolina (Tassi), Pythium debaryanum (Hesse), and Rhizoctonia solani Nees. Lower homologues were less effective, whereas compounds such as 4-methyl-6-butyl-alpha-pyrone, 4-methyl-6-pentyl-alpha-pyrone, 4-methyl-6-hexyl-alpha-pyrone, and 4-methyl-6-heptyl-alpha-pyrone were found effective against all of the test fungi. They inhibited mycelial growth by approximately 50% (ED50) at 15-50 microg/mL. 4-Methyl-6-hexyl-alpha-pyrone, which was found most effective, was tested against S. rolfsii in a greenhouse at 1, 5, and 10% concentrations. The 10% aqueous emulsion of 4-methyl-6-hexyl-alpha-pyrone suppressed disease development in tomato by 90-93% as compared with the untreated infested soil in the greenhouse after 35 days of treatment.     

Determination of cellular carbohydrates in peanut fungal pathogens and baker's yeast by capillary electrophoresis and electrochromatography.

In this work, the quantitation of cellular carbohydrates, namely chitin and glucan, in peanut fungal pathogens and baker's yeast was carried out by capillary electrophoresis (CE) and capillary electrochromatography (CEC). The chitin and glucan of the fungi were hydrolyzed by the enzymes chitinase and glucanase, respectively, to their corresponding sugar monomers N-acetylglucosamine (GlcNAc) and glucose (Glc). These two monosaccharides were then tagged with 6-aminoquinoline (6-AQ) to allow their separation and detection in CE and CEC. The 6-AQ derivatives of GlcNAc and Glc formed the basis for the determination by CE and CEC of chitin and glucan in peanut fungi and baker's yeast. Several parameters affecting the separation of the 6-AQ derivatives of GlcNAc and Glc, including the separation voltage and the composition of the running electrolyte, were investigated. Under the optimized separation conditions, the contents of cellular carbohydrates including N-acetylglucosamine, chitin, glucose, and glucan in some fungi, such as Sclerotinia minor, Sclerotium rolfsii, and baker's yeast, were successfully determined. The method described here allowed the assessment of genetic differences in Sclerotium rolfsii isolates from various locations.     

Isolation, characterization and antifungal activity of major constituents of the Himalayan lichen Parmelia reticulata Tayl

Antifungal activity of hexane, ethyl acetate and methanol extracts of Parmelia reticulata was evaluated against soilborne pathogenic fungi, namely, Sclerotium rolfsii, Rhizoctonia solani, R. bataticola, Fusarium udum, Pythium aphanidermatum and P. debaryanum by poisoned food technique. Maximum antifungal activity was exhibited by hexane and ethyl acetate extracts against most of the test pathogens. Secondary metabolites, namely, (±)-isousnic acid, (±)-protolichesterinic acid, atranorin, evernyl, ethyl hematommate, ethyl orsellinate, methyl hematommate (3-formyl-2,4-dihydroxy-6-methylbenzoic acid methyl ester), 2-hydroxy-4-methoxy-3,6-dimethylbenzoic acid, 1-hydroxy-3,6-dimethoxy-8-methyl-xanthen-9-one, baeomycesic acid and salazinic acid, were isolated from the above extracts and identified by 1H NMR, 13C NMR and mass spectroscopic methods. When these metabolites were tested for antifungal activity against test pathogens, maximum antifungal activity was exhibited by (±)-protolichesterinic acid against R. solani (ED50=23.09 μg mL(-1)) and P. debaryanum (ED50=16.07 μg mL(-1)) and by atranorin against S. rolfsii (ED50=39.70 μg mL(-1)). The antifungal activity of protolichesterinic acid was found to be comparable to that of hexaconazole, a commercial fungicide.     

Fungistatic and bacteriostatic activities of alkamides from Heliopsis longipes roots: affinin and reduced amides

This work demonstrates the fungistatic and bacteriostatic activities of affinin, the main alkamide of Heliopsis longipes (Gray) Blake (Asteraceae) roots and two alkamides obtained by catalytic reduction of affinin: N-isobutyl-2E-decenamide and N-isobutyl-decanamide. The bioactivity was tested against Rhizoctonia solani groups AG3 and AG5, Sclerotium rolfsii, Sclerotium cepivorum, Fusarium sp., Vertcillium sp., phytopathogenic fungi; Phytophthora infestans, a phytopathogenic Chromista; Saccharomyces cerevisiae, a nonphytopathogenic ascomycete; and Escherichia coli, Erwinia carotovora, and Bacillus subtilis, bacteria. Affinin, being the primary component of the lipidic fraction, is expected to be responsible for the fungitoxic activity observed in roots of this plant species. Four of the assayed fungi showed an important sensitivity to the presence of affinin: S. rolfsii, S. cepivorum, P. infestans, and R. solani AG-3 and AG-5, displaying a growth inhibition of 100%. S. cerevisiaeshowed a similar growth inhibition with affinin. None of the alkamides obtained by catalytic reduction of affinin showed a fungitoxic activity. Affinin had a definite negative effect on the growth of E. coli and B. subtilis, but E. carotovora carotovora was not sensitive to the highest dose of affinin assayed. N-Isobutyl-2E-decenamide displayed a higher bacteriostatic activity against E. coli and E. carotovora carotovora. In both cases, this alkamide was more potent than affinin. On the other hand, only N-isobutyl-decanamide displayed a significant activity on the growth of B. subtilis.     

一株从金钱树上分离的产纤维素降解酶的菌株的分离及特性鉴定

本研究从金钱树（Zamioculcas zamiifolia）白绢病（Southern blight）病株上分离到一株产纤维素酶菌株SM,经形态观察和rDNA—ITS序列分析鉴定为齐整小核菌（Sclerotium rolfsii Sacc）,经以羧甲基纤维素钠为唯一碳源的培养基培养和刚果红染色测定,证明SM菌株可产生高活性纤维素降解酶。本文对SM菌株产纤维素降解酶的液态发酵条件进行了研究,结果表明：在起始pH6．0,无机氮：有机氮：纤维素碳源之比为0．07g：1．4g：1．6g,温度为30℃,摇床转速为160r／min,发酵培养时间为5d的条件下,该菌株发酵液的CMC酶活性达到11．7U／mL,滤纸酶活性达到2．156U／mL,β-葡萄糖苷酶活性达到3．911U／mL。     

Volatile compounds emitted by sclerotia of Sclerotinia minor,Sclerotinia sclerotiorum,and Sclerotium rolfsii

Volatile compounds emitted by sclerotia of Sclerotinia minor, Sclerotinia sclerotiorum, and Sclerotium rolfsii were identified by solid phase microextraction followed by gas chromatography and mass spectometry. Both S. minor and S. sclerotiorum emitted 2-methylenebornane and 2-methylisoborneol. In addition, S. minor emitted mesityl oxide, gamma-butyrolactone, cis- and trans-linalool oxide, linalool, and trans-nerolidol. S. sclerotiorum emitted 2-methyl-2-bornene, 1-methylcamphene, and a diterpene with a molecular weight of 272. Sclerotium rolfsii did not emit any of these compounds but did emit delta-cadinene and cis-calamenene. Chemicals emitted by S. minor and S. sclerotiorum were tested to determine if they could stimulate germination of conidia of Sporidesmium sclerotivorum, a mycoparasite on sclerotia of Sclerotinia spp. Chemicals were tested at 1 part per billion to 100 parts per million, both in direct contact with conidia and near, but not in, physical contact. None of the chemicals alone nor a combination of all chemicals induced germination of conidia of S. sclerotivorum.     

An efficient method for the purification and characterization of nematicidal azadirachtins A,B, and H,using MPLC and ESIMS

Azadirachtin A enriched concentrate containing 60% active ingredient (a.i.) was prepared from the methanolic extract of the de-fatted neem (Azadirachta indica A. Juss) seed kernels. Azadirachtins A, B, and H, the three major bioactive constituents of neem seed kernel, were purified from this methanolic concentrate by employing reverse phase medium-pressure liquid chromatography (MPLC), using methanol-water solvent system as an eluant. The three pure azadirachtin congeners thus obtained were characterized by their unique mass spectral fragmentation, using electrospray probe in positive ion mode (ESI). All three azadirachtins exhibited nematicidal and antifungal activities. Azadirachtin B was the most effective against the reniform nematode Rotylenchulus reniformis (EC(50) 96.6 ppm), followed by Azadirachtin A (119.1 ppm) and H (141.2 ppm). At 200-ppm concentration, the test compounds caused 50-65% mortality of Caenorhabditis elegans nematode. Azadirachtin H showed the highest activity against the phytophagous fungi Rhizoctonia solani (EC(50) 63.7 ppm) and Sclerotium rolfsii (EC(50) 43.9 ppm), followed by B and A. The isolation of pure azadirachtins A, B, and H directly by MPLC purification from its concentrate and their characterization by ESIMS are unique and less time-consuming.     

Comparaison des aptitudes parasitaires de clones de Trichoderma vis-a-vis de quelques champignons a sclerotes

Nineteen monoconidial isolates (referred to as clones) of Trichoderma from different species aggregates, one isolate of Gliocladium virens, and one isolate of an Acrostalagmus sp. (that was naturally associated with sclerotia of Sclerotinia spp and Macrophomina phaseolina) were tested. They were incubated in controlled conditions, in sterile soil, with sclerotia of Corticium rolfsii, Sclerotinia minor, or S. sclerotiorum. At the end of appropriate periods of incubation (respectively 26, 20 and 8 days), the sclerotia were retrieved from soil and checked for invasion by the antagonist. Important differences between the parasitic ability of Trichoderma clones were noted. Clones from at least three different species (T. aureoviride, T. hamatum, T. harzianum) exhibited a high antagonistic activity. Activity of the G. virens isolate was at the same level as the best clones of Trichoderma, whereas no parasitic tendencies were found in the isolate of Acrostalagmus sp., thus confirming previous results.A rather good correlation was found between the capacity of the clones for attacking C. rolfsii sclerotia and their ability to parasitize both Sclerotinia.In conclusion, it is proposed that a screening with only one of the sclerotial species would give clones efficient against all three, and possibly against related sclerotial types.     

Effects of solarization of soil on nematode and fungal pathogens at two sites in victoria

The effect of covering soil with transparent polyethylene sheets, known as soil solarization, on the viability of plant pathogens was determined. The treatment was tested in mid-summer on sandy loams in N.W. and S. Victoria. Columns of moist soil were inoculated with one of a variety of pathogens, viz. Fusarium oxysporum, Pythium irregulare, Plasmodiophora brassicae, Sclerotium cepivorum, S. rolfsii, Sclerotinia minor, Verticillium dahliae and the nematodes Macroposthania xenoplax, Meloidogyne javanica, Pratylenchus penetrans and Tylenchulus semipenetrans. Columns were placed vertically in soil, and then treated either for 4 weeks in N.W. Victoria, or 6 weeks in S. Victoria.Preliminary laboratory tests showed that pathogens were killed by temperatures within the range 38–55°C. The relative sensitivities of pathogens to fluctuating soil temperatures were similar at both sites. The most sensitive were the nematodes, and the fungi V. dahliae, S. cepivorum and S. minor, while F. oxysporum, P. irregulare and P. brassicae were the least sensitive. In N.W. Victoria treatment effects were apparent to 26 cm and most pathogens were not recovered from 0 to 11 cm. In S. Victoria treatment effects were apparent to a depth of 16cm and most pathogens were not recovered from 0 to 6cm.     

Sclerotium rolfsii dynamics in soil as affected by crop sequences

Crop rotation has been used for the management of soilborne diseases for centuries, but has not often been planned based on scientific knowledge. Our objective was to generate information on Sclerotium rolfsii dynamics under different crop or intercrop activities, and design and test a research approach where simple experiments and the use of models are combined to explore crop sequences that minimize Southern blight incidence.The effect of seventeen green manure (GM) amendments on sclerotia dynamics was analyzed in greenhouse and field plot experiments during two years. The relative densities of viable sclerotia 90 days after winter GM (WGM) incorporation were generally lower than after summer GM (SGM) incorporation, with average recovery values of 60% and 61% for WGM in the field, 66% and 43% for WGM in the greenhouse, and 162% to 91% for SGM in the greenhouse, in 2009 and 2010, respectively. Sclerotia survival on day d after GM amendment was described by the model S_f = S_i × exp(−b × d), relating initial (S_i) and final (S_f) sclerotia densities. Relative decay rates of the sclerotia (b) in SGM amended soil were largest for alfalfa (0.0077 ± 0.0031 day⁻¹) and sudangrass (0.0072 ± 0.0030 day⁻¹). In WGM amended soil, the largest b values were for oat (0.0096 ± 0.0024 day⁻¹), wheat (0.0090 ± 0.0024 day⁻¹) and alfalfa (0.0087 ± 0.0023 day⁻¹).The effect of three cropping sequences (sweet pepper–fallow, sweet pepper–black oat and sweet pepper–onion) on sclerotia dynamics was analyzed in microplot experiments, and the data were used to calibrate the model P_f = P_i/(α + βP_i), relating initial (P_i) and final (P_f) sclerotia densities. Median values for the relative rate of population increase at low P_i (1/α, dimension less) and the asymptote (1/β, number of viable sclerotia in 100 g of dry soil) were 8.22 and 4.17 for black oat (BO), 1.13 and 8.64 for onion (O), and 6.26 and 17.93 for sweet pepper (SwP).By concatenating the two models, sclerotia population dynamics under several crop sequences were simulated. At steady state, the sequence SwP–O–Fallow–BO resulted in the lowest long-term sclerotia density (7.09 sclerotia/100 g soil), and SwP–Fallow in the highest (17.89 sclerotia/100 g soil). The developed methodology facilitates the selection of a limited number of rotation options to be tested in farmers’ fields.     

Formation of carcinogenic 4(5)-methylimidazole in Maillard reaction systems

4(5)-Methylimidazole has received the attention of federal and state regulatory agencies because of its carcinogenicity and common presence in foods and beverages. In the present study, the formation of 4(5)-methylimidazole in Maillard reaction model systems consisting of D-glucose/NH(3), L-rhamnose/NH(3), methylglyoxal/NH(3), and methylglyoxal/formaldehyde/NH(3) was investigated. 4(5)-Methylimidazole was formed at levels ranging from 0.49 to 0.71 mg/mL in the d-glucose/NH(3) model system. The formation of 4(5)-methylimidazole was slightly higher in the L-rhamnose/NH(3) system (0.91 mg/mL) than in the d-glucose/NH(3) system (0.71 mg/mL) under the conditions used in the present study. A methylglyoxal/NH(3) system produced significantly higher levels of 4(5)-methylimidazole (5.70 mg/mL), suggesting that methylglyoxal is an important precursor of 4(5)-methylimidazole. Ammonolysis of methylglyoxal, which is one of the glucose degradation products, was proposed to form formamide, which subsequently reacted with 2-aminopropanal (α-aminocarbonyl intermediate) formed from methylglyoxal to give 4- or 5-methylimidazole. The levels of 4(5)-methylimidazole found in commercial cola soft drinks range from 0.30 μg/mL (brand 3) to 0.36 μg/mL (brands 1 and 5).     

天山林区不同地段6种灌木生物量组成

分布于天山云杉林下线的山地灌丛是天山重要的植被类型之一,也是天山相对稳定的生态系统类型,在天山水土保持中发挥着重要的作用。以天山6种常见的灌木为研究对象,在天山西部、中部、东部设置调查样地,并用平均标准木收获法获得6种常见灌木各营养器官的生物量。从而探讨了6种灌木在天山三段的分布特征以及各营养器官的分配差异。结果表明:（1）同种灌木在天山西部、中部、东部单株生物量存在着差异,其中天山西部6种灌木生物量明显大于天山中部和东部。主要是由于天山西部水热条件优于天山中部和东部;（2）在天山6种常见灌木类型中,单株生物量从大到小排序为:刚毛忍冬（8 549 g/株） > 黑果栒子（7 943 g/株） > 黑果小檗（7 880 g/株） > 新疆方枝柏（3 014 g/株） > 天山绣线菊（2 837 g/株） > 密刺蔷薇（2 615 g/株）;（3）天山6种常见灌木在天山三段各器官生物量分配比例不同,天山西部主要表现为枝生物量（53.30%）大于根生物量（27.32%）,而天山中部和东部则为根生物量（75.90%）大于枝生物量（19.06%）,这种分配比例的差异体现了物种对其生境选择的适应性。本研究结果可为对于天山灌丛植被的保护及其退化生态系统的恢复重建提供科学依据。     

Nutrient deficiency in the production of artemisinin, dihydroartemisinic acid, and artemisinic acid in Artemisia annua L

Artemisia annua became a valuable agricultural crop after the World Health Organization recommended artemisinin as a component of ACT (artemisinin-combination based therapies) for malaria in 2001. A cloned, greenhouse-grown, A. annua (Artemis) subjected to an acidic soil and macronutrient deficit was evaluated for artemisinin production. Lack of lime (L) and macronutrients (N, P, and K) reduced leaf biomass accumulation. When L was provided (pH 5.1), the highest average leaf biomass was achieved with the "complete" (+N, +P, +K, and +L) treatment (70.3 g/plant), and the least biomass was achieved with the untreated (-N, -P, -K, and -L) treatment (6.18 g/plant). The nutrient least required for biomass accumulation per plant (g) was K (49.0 g), followed by P (36.5 g) and N (14.3 g). The artemisinin concentration (g/100 g) was significantly higher (75.5%) in -K plants when compared to plants under the complete treatment (1.62 vs 0.93%). Although the artemisinin total yield (g/plant) was 21% higher in -K plants, it was not significantly different from plants under the complete treatment (0.80 vs 0.66 g/plant). There were no marked treatment effects for concentration (g/100 g) or yield (g/plant) of both dihydroartemisinic acid and artemisinic acid, although higher levels were achieved in plants under the complete or -K treatments. There was a positive and significant correlation between artemisinin and both artemisinic acid and dihydroartemisin acid, in g/100 g and g/plant. This is the first report where potassium deficiency significantly increases the concentration (g/100 g) of artemisinin. Thus, under a mild potassium deficiency, A. annua farmers could achieve similar gains in artemisinin/ha, while saving on potassium fertilization, increasing the profitability of artemisinin production.     

Effects of combined and sequential addition of dual oxidants (H2O2/S2O8(2-)) on the aqueous carbofuran photodegradation

Carbofuran (2,3-dihydro-2,2-dimethylbenzofuran-7-yl methylcarbamate) (CBF) is a widely used insecticide. Traditional methods like hydrolysis and direct photolysis cannot remove CBF effectively. In this study, the photodecay of 0.1 mM CBF in UV/H2O2, UV/S2O8(2-), and UV/H2O2/S2O8(2-) and sequential addition of a second oxidant were studied under UV light at 254 nm. The degradations of CBF follow pseudo-first-order decay kinetics. Direct photolysis was slow, but the corresponding degradation rate was increased with the addition of hydrogen peroxide (H2O2) or potassium peroxydisulfate (K2S2O8). In the UV/H2O2 reaction, the optimum reaction rate was 0.9841 min-1 at 10 mM H2O2 (pH 7); however, retardation is observed if H2O2 is overdosed. Such retardation is not observed in the UV/S2O8(2-) system, but a nonlinear increment of removal efficiency is identified. The UV/H2O2/S2O8(2-) process on the other hand shows the best performance in CBF degradation, but it has a less effective mineralization than that of the sole UV/S2O8(2-) reaction.     

广州市蔬菜和菜地土壤砷含量及其健康风险研究

测定了广州市郊区菜地土壤(n=120)、菜地蔬菜(n=109)和市售蔬菜(n=237)中砷含量,结合广州居民蔬菜消费情况,分析了砷对广州居民的健康风险影响.结果表明:不同类型菜地土壤砷含量不同,为菜园土(12.94±9.78)mg/kg>水稻土(8.67±10.24)mg/kg>赤红壤(4.17±3.70)mg/kg,土壤质量主要属于二级标准以内;菜地蔬菜砷含量范围为ND～0.179 mg/kg,均值为(0.017±0.024)mg/kg;市售蔬菜砷含量范围为ND-0.314 mg/kg,含量变化为豆类(0.038±0.047)mg/kg)>根茎类(0.027±0.031)mg/kg>茄类(0.025±0.030)mg/kg>叶菜类(0.024±0.022)mg/kg>葱蒜类(0.019±0.025)mg/kg>瓜类(0.017±0.020)mg/kg,所有蔬菜均没有超过我国食品中砷的限量卫生标准(GB-4810-94).广州市居民从蔬菜中摄入的砷为0.045 mg/d,叶菜类和根茎类蔬菜是主要的贡献者.     

Rapid and sensitive HILIC-ESI-MS/MS quantitation of polar metabolites of acrylamide in human urine using column switching with an online trap column

The carcinogen acrylamide (AA) is formed during the processing of food. AA is metabolized to mercapturic acids, which are excreted with urine. A hydrophilic interaction liquid chromatography tandem mass spectrometry method (HILIC-MS/MS) using a zwitterionic stationary phase (Zic-HILIC) was developed and validated to quantitate the mercapturic acids of AA (AAMA) and glycidamide (GAMA), and AAMA-sulfoxide in human urine. In contrast to reversed phases, the application of Zic-HILIC resulted in efficient retention and separation of these highly polar compounds. Off-line sample workup was avoided by application of column switching with a Stability BS-C17 trap column prior to the analytical column, thus minimizing interferences with the urinary matrix. Limit of quantification values (LOQs) were 0.5 microg/L (AAMA), 2.0 microg/L (AAMA-sulfoxide), and 1.0 microg/L (GAMA) in human urine. Median concentrations in urine samples ( n = 54) of six nonsmoking human subjects were 24.0 microg/L (AAMA, 7.8-79.8 microg/L), 16.7 microg/L (AAMA-sulfoxide, 6.8-70.1 microg/L), and 3.82 microg/L (GAMA, 1.0-23.6 microg/L).     

Using the simplified falling head technique to detect temporal changes in field-saturated hydraulic conductivity at the surface of a sandy loam soil

Determining temporal changes in field-saturated hydraulic conductivity (K_fs) is important for understanding and modeling hydrological phenomena at the field scale. Little is known about temporal variability of K_fs values measured at permanent sampling points. In this investigation, the simplified falling head (SFH) technique was used for an approximately 2-year period to determine temporal changes in K_fs at 11 permanent sampling points established at the surface of a sandy loam soil. Additional K_fs measurements were obtained by the single-ring pressure infiltrometer (PI) technique to also compare the SFH and PI techniques. The lowest mean values of K_fs, M(K_fs), were detected in December and January (20.5 ≤ M(K_fs) ≤ 146.2 mm h⁻¹), whereas higher results (190.5 ≤ M(K_fs) ≤ 951.9 mm h⁻¹) were obtained in the other months of the year. The K_fs values were higher and less variable in the dry soil (θ_i ≤ 0.21 m³ m⁻³, M(K_fs) = 340.6 mm h⁻¹, CV(K_fs) = 106%) than in the wet one (θ_i > 0.21 m³ m⁻³, M(K_fs) = 78.4 mm h⁻¹, CV(K_fs) = 185%). Both wet and dry soil were less conductive at the end of the study period than at the beginning one but a more appreciable change was detected for the dry soil (K_fs decreasing by 83.4%) than for the wet one (K_fs decreasing by 63.0%). The simple SFH technique yielded K_fs results similar to the more laborious and time-consuming PI technique (i.e., mean values differing at the most by a factor of two). It was concluded that (i) the soil water content was an important factor affecting the K_fs results obtained in a relatively coarse-textured soil, (ii) the impact of time from the beginning of the experiment on the saturated hydraulic conductivity was larger for a repeated sampling of dry soil than of wet soil and (iii) the SFH technique yielded reliable K_fs results in a relatively short period of time without the need for extensive instrumentation or analytical methodology.     

Identification and quantification of carotenoids including geometrical isomers in fruit and vegetable juices by liquid chromatography with ultraviolet-diode array detection

A method was established for the identification and quantification of carotenoids including geometrical isomers in fruit and vegetable juices by liquid chromatography with an ultraviolet-diode array detector, using a C(18) Vydac 201TP54 column. The mobile phase used was the ternary methanol mixture (0.1 M ammonium acetate), tert-butyl methyl ether and water, in a concentration gradient, and a temperature gradient was applied. Retinol palmitate was added as an internal standard. An extraction process (ethanol/hexane, 4:3, v/v) was performed, followed by saponification with diethyl ether/methanolic KOH (0.1%, w/v, BHT) (1:1, v/v) for 0.5 h at room temperature. Seventeen different (cis and trans) carotenoids were identified by UV-vis spectra and retention times in HPLC in the juices analyzed. The analytic parameters show that the method proposed is sensitive, reliable, accurate, and reproducible.     

播期和水氮互作对滴灌施肥春玉米生长和水氮利用的影响

  【目的】  河西地区石羊河流域的农业生产中水资源短缺，光热资源利用率和水肥利用效率低。通过调整播期协调光热资源与水肥供应，研究提高春玉米生长及水肥利用效率的可能性。  【方法】  大田滴灌试验于2018年在甘肃省中国农业大学石羊河流域农业与生态节水试验站进行。设置3个播种日期，即4月10日 (S₁)、4月20日 (S₂)、4月30日 (S₃)；2个灌水量水平，即80% ET_c (I₈₀)、100% ET_c (I₁₀₀) (ET_c为作物蒸发蒸腾量)；4个施氮量水平，即N 0、120、180、240 kg/hm2，分别表示为N₀、N₁₂₀、N₁₈₀、N₂₄₀。在玉米生长关键期，测定植株生长状况和水分利用指标，收获期测产。  【结果】  播期对春玉米各生育阶段的持续时间影响显著，生育期天数随着播期的推迟呈缩减趋势，合理播期应避免灌浆期的高温辐射和降雨量过多。除耗水量外，施氮量对其它各指标影响显著。叶面积指数、干物质积累量和产量均随灌水量增加而增加，随施氮量增加而上升，产量随播期的推迟而减少。S₁I₁₀₀N₁₈₀处理产量最大，为16830 kg/hm2，比S₂I₁₀₀N₂₄₀处理增产7.35%、节肥14.29%，比S₃I₁₀₀N₁₈₀处理增产12.55%。水分利用效率随施氮量增大而增加，随灌水量增大而升高。S₁I₁₀₀N₁₈₀处理水分利用效率为3.1 kg/m3，比S₁I₈₀N₂₄₀处理高12.32%。氮肥偏生产力随施氮量增大而减小，S₁I₁₀₀N₁₈₀处理氮肥偏生产力为93.5 kg/kg，比S₁I₁₀₀N₁₂₀处理降低4.9%，但增产42.65%。  【结论】  综合产量和节水节肥因素，在本试验条件下适时早播 (4月10日) 有助于充分发挥水肥资源的潜力。在早播和充分灌水条件下，施用较低的氮肥量 (N 180 kg/hm2) 即可获得最高的产量。