Residue levels and storage responses of nectarines, apricots, and peaches after dip treatments with fludioxonil fungicide mixtures

Mature apricots (Prunus armeniaca), nectarines [Prunus persica var. nectarine (Ait.)], and peaches [P. persica (L.) Batsch.] were subjected to a 2 min dip treatment with warm water at 48 degrees C or with fludioxonil (FLU) at 100 mg L-1 and 20 degrees C or at 25 mg L-1 FLU and 48 degrees C and then stored at 5 degrees C and 90-95% relative humidity (RH) for 1 week plus 1 additional week at 18 degrees C and approximately 80% RH. Fruit residue uptake was determined as a function of fungicide concentration, dip temperature, treatment time (only on nectarines), and fruit storage conditions. FLU residue level was closely related to fungicide concentration and treatment temperatures and was dependent on fruit species. FLU residues showed great persistence over both storage and shelf life. Fruit dipping in water at 48 degrees C effectively reduced decay development in cvs. 'May Grand' nectarines and 'Pelese' apricots but was ineffective in cvs. 'Red Top' and 'Sun Crest' nectarines during 7 days of storage compared with nontreated fruit. Decay rates in cvs. 'Glo Haven' peaches and 'Fracasso' apricots were very low in fruit dipped in water at both 20 and 48 degrees C. Fungicide treatments at 20 and 48 degrees C resulted in the total or almost total suppression of decay in all cultivars. During shelf life, fruit became very prone to decay, averaging 25.7-100% depending on the cultivar. Fruit dipping in hot water effectively reduced decay in 'Pelese' and 'Fracasso' apricots, 'Sun Crest' peaches, and 'May Grand' nectarines as compared to control, but was ineffective in 'Glo Haven' and 'Red Top' peaches. Fungicide treatments at 20 degrees C were more effective than hot water in most cultivars. The combination of FLU with water at 48 degrees C further improved the fungicide performance. Indeed, reduced levels (a fourth) of active ingredient were required to achieve a control of decay comparable to that for treatment at 20 degrees C. Residue levels in fruit after treatment with 100 mg L-1 FLU at 20 degrees C or with 25 mg L-1 FLU at 48 degrees C averaged approximately 0.6-2 mg kg-1, which were notably lower than the maximum residue limit (5 mg kg-1) allowed in the United States for stone fruit.     

Effect of fungicide treatment on the quality of wheat flour and breadmaking

Fungicides are applied to crop plants to ensure disease protection and improve growth. To assess the effects of five commercial foliar and spike fungicides in four different combinations on wheat (Triticum aestivum L.), various quality parameters and flour processing properties, including baking quality, were determined. Three commonly used wheat cultivars with different quality classes (E, B, and C) were tested. Falling number, crude protein content, water absorption ability, protease activity, viscosity, and the free amino acid content were mainly lower in the fungicide-treated grains than in the untreated grains. None of the fungicides caused any significant changes in the wet gluten content, dough properties, the mono- and oligosaccharide content, or the breadmaking quality. In general, the commercial fungicide treatments did not cause any statistically significant differences between the treated and the untreated samples with respect to the quality parameters analyzed, although there were indeed significant differences between the three cultivars themselves.     

Compatibility of Mesorhizobium sp. Cicer with seed treatment of fungicide and insecticide in chickpea

This investigation was undertaken to study the compatibility of Mesorhizobium sp. Cicer with captan (fungicide) and chlorpyrifos (insecticide) for growth, symbiotic parameters and yield in chickpea. In an in vitro experiment, a significant reduction in the number of viable mesorhizobia was observed in Mesorhizobium sp. Cicer treated chickpea seeds at the recommended doses of captan (3 g kg^?1 seed) and chlorpyrifos (10 ml kg^?1 seed) after 4 h storage at 4°C, and further reduction was seen after 8–16 h contact with Mesorhizobium. The results showed that captan was more toxic than chlorpyrifos. In field experiments, improved growth and symbiotic parameters (plant height, dry weight of shoot, nodulation, leghaemoglobin content, chlorophyll content and nitrogen content) and a reduction in per cent damaged by termites and diseases were observed in the Mesorhizobium alone treatment compared with the uninoculated control. Grain yield was increased significantly in treatments with Mesorhizobium alone or in a mixture with fungicide and insecticide (captan and chlorpyrifos) compared with the control treatment. It is evident that chemically treated seeds should always be sown as soon as possible after inoculation. Recommended rates of captan and chlorpyrifos application with Mesorhizobium inoculant as a seed treatment was innocuous to chickpea–Mesorhizobium symbiosis.     

Kinetic limitations on the selective precipitation treatment of electronics wastes

Laboratory studies on the precipitation of metals from a synthetic wastewater simulating the composition of semiconductor manufacturing were performed. Residual soluble metals, in many cases, were dependent upon the age of the waste prior to precipitation. Based upon these studies, it was concluded that equilibrium information alone does not provide a complete understanding of metal removal by chemical precipitation.     

Residue level, persistence, and storage performance of citrus fruit treated with fludioxonil

The potential of postharvest dip treatments with fludioxonil (FLU) (a synthetic analogue of the bacterial metabolite of pyrrolnitrin), in controlling postharvest decay caused by Penicillium digitatum and Penicillium italicum of citrus fruit was investigated in comparison with the conventional fungicide imazalil (IMZ). The ultrastructural changes of fruit epicuticular wax was investigated as a function of water dip temperature, and the possible role of these changes was related to residue accumulation under FLU treatment. Residues retained by fruit were determined as a function of fungicide concentration, dip temperature, and fruit storage conditions. Scanning electron microscopy analysis revealed that fruit dipping in water at 30 or 40 degrees C did not cause differences in cuticular wax's ultrastructure in comparison to control fruit, while treatments at 50, 55, or 60 degrees C caused the disappearance of wax platelets, resulting in relatively homogeneous skin surface, due to partial "melting" of epicuticular wax. Residues of FLU in fruit treated at 20 or 50 degrees C were significantly correlated with the doses of fungicide applied. When equal amounts of fungicide were employed, the residue concentrations were notably higher (from 2.6- to 4-fold) in fruit treated at 50 degrees C than in fruit treated at 20 degrees C. The dissipation rate of FLU in "Salustiana" and "Tarocco" oranges was lower in fruit subjected to treatment at 50 degrees C. The minimal FLU concentration for almost complete decay control in artificially wounded fruit during 7-d storage at 20 degrees C was 400 mg/L active ingredient (ai) in fruit treated at 20 degrees C and 100 mg/L ai in fruit treated at 50 degrees C. Results on nonwounded Tarocco oranges subjected to 3 weeks of simulated quarantine conditions at 1 degrees C, plus 6 weeks of standard storage at 8 degrees C and an additional two weeks of simulated marketing period (SMP) at 20 degrees C revealed that almost complete decay control with FLU applications of 100 mg/L at 50 degrees C and 400 mg/L at 20 degrees C resulted in ca. 0.8 mg/kg FLU fruit residues, in agreement with results on wounded citrus fruit. When equal concentrations and temperatures were applied, FLU treatments were as effective as IMZ. In vitro trials showed a low sensitivity to FLU against P. digitatum and P. italicum isolates. MIC values for the complete inhibition of mycelium growth were >or=100 microg/mL, while ED(50) values ranged from 0.1 to 1 microg/mL for P. digitatum and from 1 to >100 microg/mL for P. italicum. The latter result suggests that care should be taken to avoid exclusive application of FLU in a sustainable program for management of fruit decay. However, integrating fungicide application and hot water dip may reduce the possibility of selecting fungicide-resistant populations of the pathogen, by increasing the effectiveness of the treatment.     

Glutathione-dependent biotransformation of the fungicide chlorothalonil

A gene responsible for the chlorothalonil biotransformation was cloned from the chromosomal DNA of Ochrobactrum anthropi SH35B, capable of efficiently dissipating the chlorothalonil. The gene encoding glutathione S-transferase (GST) of O. anthropi SH35B was expressed in Escherichia coli, and the GST was subsequently purified by affinity chromatography. The fungicide chlorothalonil was rapidly transformed by the GST in the presence of glutathione. LC-MS analysis supported the formation of mono-, di-, and triglutathione conjugates of chlorothalonil by the GST. The monoglutathione conjugate was observed as an intermediate in the enzymatic reaction. The triglutathione conjugate has not been previously reported and seems to be the final metabolite in the biotransformation of chlorothalonil. The glutathione-dependent biotransformation of chlorothalonil catalyzed by the bacterial GST is reported.     

Transformation of the fungicide chlorothalonil by Fenton reagent

A modified Fenton reagent (Fe(3+)/H(2)O(2)) transformed the fungicide chlorothalonil within 60 min in aqueous solution at unadjusted pH. Transformation varied with ferric salt. Transformation was greatest with ferric nitrate and least when ferric sulfate was used. UV irradiation enhanced the transformation of chlorothalonil. The transformation of chlorothalonil was enhanced, which increased with ferric ion or hydrogen peroxide concentration. Maximum transformation was achieved at 2 mM ferric ion and 100 mM hydrogen peroxide. Additionally, chlorothalonil was more dechlorinated in the UV irradiation condition. The proposed reaction pathway includes reduction of chlorothalonil to trichloroisophthalonitrile, dichloroisophthalonitrile, and monochloroisophthalonitrile; oxidation of trichloroisophthalonitrile to trichloro-3-cyanobenzoic acid and 3-carbamyltrichlorobenzoic acid; and oxidation of hydroxychlorothalonil to trichloro-3-cyanohydroxybenzoic acid and trichlorocyanophenol.     

Determination of the fungicide validamycin A by capillary zone electrophoresis with indirect UV detection

Validamycin A, a main component of the antibiotic validamycin complex, which is widely used to control sheath blight disease of rice plants, can be determined by capillary zone electrophoresis with indirect UV detection. The influence of various separation conditions including background electrolyte and modifier concentration, pH, and voltage was investigated. By using 10 mM aminopyrine-2 mM ethylenediaminetetraacetic acid at pH 5.2 as the carrier electrolyte, high efficiency separation of validamycin A was achieved with the number of theoretical plates up to 350000 plates/m. The linear range was across 3 orders of magnitude. The relative standard deviations for migration times and peak areas were less than 0.5 and 3.0%, respectively. The limit of detection for validamycin A was 1.0 microg/mL. The average recoveries ranged from 103.0 to 104.8%. This method has many advantages as compared with high-performance liquid chromatography and micellar electrokinetic capillary chromatography in the determination of commercial formulations.     

The toxicity of the fungicide propiconazole to soil flagellates

 We investigated the effects of the ergosterol-inhibiting fungicide, propiconazole {1-[[2-(2,4-dichlorphenyl) - 4 - propyl - 1,3 - dioxolan - 2 - yl]methyl] - 1H - 1,2,4 triazole; Tilt}, on mixed natural populations of bacterivorous and fungivorous flagellates in soil and on single species of bacterivorous flagellates in liquid culture. The fungicide affected a mixed natural population of fungivorous flagellates less than the population of bacterivorous flagellates. Our results indicated that the effects of propiconazole on flagellates are direct toxic effects and not effects mediated via their food. All tested types of flagellates were significantly harmed when exposed to the concentration of propiconazole normally applied to agricultural fields (625 mg l^–1). However, when exposed to the concentration of propiconazole which we expect in the soil water phase after application (ca. 0.6 mg l^–1) the effect on most of the tested flagellates was slight. Still, one tested flagellate species, Dimastigella trypaniformis, was extremely sensitive to the compound, and it is possible that field application of propiconazole has negative effects on certain sensitive species, and therefore alters the composition of the soil flagellate community in the direction of a higher r/K ratio. Received: 7 April 1999     

磁化处理促进施氮条件下葡萄氮素的代谢和分布

以‘夏黑’葡萄扦插苗为试验材料,采用盆栽试验方法,分析了磁化水灌溉后葡萄叶片、茎和根系中不同形态氮素含量、氮素代谢关键酶活性以及不同氮源的贡献率,探讨磁化作用对‘夏黑’葡萄扦插苗生长以及氮素吸收、分配和利用的影响。以~(15)N为外源氮肥,分3次施入土壤中。试验设置4个处理,包括:磁化水灌溉处理、非磁化水灌溉处理、磁化水灌溉+施氮处理、非磁化水灌溉+施氮处理。磁化处理组中利用磁化装置处理灌溉水。结果表明:1)施氮条件下,与非磁化处理相比,磁化处理后葡萄叶片、根系和全株的全氮量提高,但是肥料中~(15)N对不同器官中氮素的贡献率无显著差异;叶片和根系的氮素利用率显著提高;全氮在叶片中分配率显著提高,在茎中的分配率则显著降低。2)与非磁化处理相比,磁化处理后葡萄叶片中谷氨酰胺合成酶和谷氨酸合酶活性显著提高,根系中显著降低。3)与单独施氮相比,磁化水灌溉+施氮提高了土壤氮含量;氮肥中~(15)N利用率提高,损失率降低。由以上研究结果可以看出,磁化水灌溉不仅可提高氮素代谢关键酶活性,而且可提高不同器官中氮素营养的吸收和利用,从而改变了氮素在不同器官中的分布。     

Determination of nabam fungicide in crops by liquid chromatography with postcolumn reaction detection

The ethylenebisdithiocarbamate (EBDC) fungicide, nabam, was determined in several crop matrixes using liquid chromatography with postcolumn reaction detection. After separation by micellar liquid chromatography, nabam (EBDC sodium salt) was acid hydrolyzed to ethylenediamine and fluorigenically labeled with o-phthalaldehyde-mercaptoethanol (OPA-MERC). Standard curves were linear from the detection limit of ca 1 ng to 1000 ng. Nabam was recovered in high yield (89 plus or minus 7.7%) over a range of concentrations (0.1 to 20 ppm) from fortified samples of papaya, lettuce, cucumber, spinach, and applesauce using a simple extraction method. Efforts to convert the more popular EBDC fungicides, maneb and mancozeb, to nabam are discussed.     

水上浮床种植水稻的光合特性及生理特点

以传统水田种植(conventional tillage,CT)为对照,对水上种植(culture in water-CW)水稻的光合特性、根系特点和部分农艺性状进行比较研究。结果发现,水稻在CW的光合速率(PN)和气孔导度(gs)增加幅度较大,根条数、根系活力和酶活性显著提高,分蘖数和有效穗数分别增加17.91%和24.07%;水分利用率、株高、结实率和千粒质量却无明显差异。结果表明,CW通过提高根系吸收能力、增加分蘖数和有效穗数及提高光合速率,达到增产的目的,是值得推广的种植方式。     

Xylem exudate concentrations of cofactor nutrients in grapevine are correlated with exudation rate

Xylem exudates collected from the cut canes of Vitis vin‐ifera L. var. Waltham Cross for 10 weeks around the time of budburst were analyzed for nutrient concentrations. The seasonal variations of the inorganic constituents examined [phosphorus (P), calcium (Ca), potassium (K), magnesium (Mg), manganese (Mn), zinc (Zn), iron (Fe), copper (Cu), sodium (Na), and chlorine (Cl)] are presented and discussed with respect to the metabolic needs of the plant as it breaks dormancy. Of particular interest was the observation that some of the nutrients (Ca, K, Mg, Mn, Zn, and Fe) showed similar seasonal variations in their concentrations. These variations were significantly correlated with the rate of xylem exudate flow. Other essential nutrients which are not enzyme cofactors did not show this variation. We propose that these variations, similar to the previously noted variation of organic acids in grapevine xylem exudate, reflect a flow‐dependent uptake and/or remobilization of nutrients to facilitate budburst through the provision of cofactors in large quantities at the critical time.     

叶轮旋转式葡萄藤埋土单边清除机研制

针对目前春季中国北方葡萄种植主产区人工进行葡萄藤清土作业效率低、机械化程度低等问题,该文设计了一种适应于单边清土的叶轮旋转式葡萄藤清土机,主要由机架、刮土部件、叶轮部件和平土搅龙部件组成。刮土部件和叶轮部件能够分别将葡萄藤上方和侧面土壤清除,平土搅龙部件能够将清除的土壤进一步向行间输送并使其均匀地平铺在葡萄行正中间。以机器前进速度、叶轮转速和搅龙转速为因素,以清土中心距为指标,在离散元软件EDEM中对葡萄藤清土机作业进行仿真试验,得到最佳工作参数:前进速度1.2 m/s、叶轮转速420 r/min、搅龙转速300 r/min,此时清土中心距为44 mm。加工物理样机并进行田间试验,田间试验结果与仿真结果基本一致,两者清土中心距的相对误差约为15%,满足葡萄藤清土机单边清土的作业要求。该研究可为后续其他类型葡萄藤清土机的研制提供参考。     

Effect of fungicide residues on the aromatic composition of white wine inoculated with three Saccharomyces cerevisiae strains

The effects of three fungicide residues (cyprodinil, fludioxonil, and pyrimethanil) on the aromatic composition (acids, alcohols, and esters) of Vitis vinifera white wines (var. Airén) inoculated with three Saccharomyces cerevisiae strains (syn. bayanus, cerevisiae, and syn. uvarum) are studied. The aromatic exponents were extracted and concentrated by adsorption-thermal desorption and were determined by gas chromatography using a mass selective detector. The addition of the three fungicides at different doses (1 and 5 mg/L) produces significant differences in the acidic fraction of the aroma, especially in the assays inoculated with S. cerevisiae, although the final contents do not exceed the perception thresholds. The lower quality wines, according to isomeric alcohol content [(Z)-3-hexen-1-ol and 3-(methylthio)propan-1-ol] are those obtained by inoculation with S. cerevisiae(syn. bayanus) and addition of cyprodinil. The addition of fungicides in the assays inoculated with S. cerevisiae (syn. bayanus) produces an increase in the ethyl acetate and isoamyl acetate contents, which causes a decrease in the sensorial quality of the wine obtained.     

Biodegradation of the fungicide iprodione by Zygosaccharomyces rouxii strain DBVPG 6399

Iprodione is a contact fungicide used to control several pathogens such as Botrytis cinerea, Monilia, and Sclerotinia. This paper reports the ability of an iprodione-resistant strain of Zygosaccharomyces rouxii to degrade iprodione at a concentration of 1 mg L(-1). The yeast Z. rouxii was chosen also for its ability to grow at high osmolarity. Also of note is that in bioremediation situations and in the food industry such resistance could be important. The kinetic and metabolic behaviors of the fungicide in the media are described. The results show a new transformation pathway of iprodione by the yeast leading to the formation of N-(3,5-dichlorophenyl)-2,4-dioxoimidazoline, 3-isopropylhydantoin, and 3,5-dichloroaniline. These compounds were identified by 1H NMR, 13C NMR, and GC-MS analyses. This study provides a basis to employ yeast strains in biodegradation studies in relation to their ability in the disappearance and degradation of xenobiotics into simpler molecules.