Development of controlled release nanoformulations of carbendazim employing amphiphilic polymers and their bioefficacy evaluation against Rhizoctonia solani

Controlled release nanoformulations of carbendazim (Methyl 1H-benzimidazol-2-ylcarbamate), a systemic fungicide, have been prepared using laboratory synthesized poly(ethylene glycols) (PEGs)-based functionalized amphiphilic copolymers. The release kinetics of carbendazim from developed controlled release (CR) formulations was studied and compared with that of the commercially available 50% Wettable Powder (WP). Further, the bioefficacy evaluation of developed formulations was done against plant pathogenic fungi Rhizoctonia solani by the poison food technique method. The release of maximum amount of carbendazim from developed formulations was dependent on the molecular weight of PEGs and was found to increase with increasing molecular weights. The range of carbendazim release was found to be between 10th to 35th day as compared to commercial formulation which was up to 7th day. The diffusion exponent (n value) of carbendazim in water ranged from 0.37 to 0.52 in the tested formulations. The half-release (t_1/2) values ranged between 9.47 and 24.20 days, and the period of optimum availability (POA) of carbendazim ranged from 9.15 to 26.63 days. Also, ED₅₀ values of the developed formulations vary from 0.40 to 0.74 mg L^?1. These formulations can be used to optimize the release of carbendazim to achieve disease control for the desired period depending on the matrix of the polymer used.     

Neighborhood quality in environmentally stressed areas of Accra, Ghana: a comparison with US counterparts

A sample of 873 residents of Accra, Ghana, stratified by type of neighborhood was gathered in order to measure the association of poor neighborhood quality with neighborhood problems and residents' personal characteristics. Strong associations were found with poor schools, physical blight, rowdy and criminal behavior, ethnic differences, and environmental problems. In addition, poor neighborhood quality was strongly associated with mistrust of authority and a feeling of a lack of control over neighborhood activities. Respondents identified road, street, drainage, sewage, and other infrastructure deficiencies as priorities to address, even though these were not prominent discriminators of neighborhood quality ratings. Many of these findings are common to counterparts in the US, but some findings appear to reflect cultural and differences in urbanization.     

Differential responses in American (<Emphasis Type="Italic">Castanea dentata</Emphasis> Marshall) and Chinese (<Emphasis Type="Italic">C. mollissima</Emphasis> Blume) chestnut (Falales: Fagaceae) to foliar application of jasmonic acid

Summary.  Tannins are plant defense compounds that exhibit antibiotic (e.g. toxic) and antixenotic (e.g. repellent) effects against an array of plant pests. They are broadly divided into two major groups, hydrolysable tannins (gallotannins and ellagitannins) and proanthocyanidins, each with an undetermined number of compounds. We investigated constitutive levels of hydrolysable tannins and proanthocyanidins in the leaves and stems of American (Castanea dentata Marshall) (Fagales: Fagaceae) and Chinese (C. mollissima Blume) chestnut. American chestnut contained more proanthocyanidins in leaves and stems than Chinese chestnut, but Chinese chestnut contained more foliar hydrolysable tannins. Regardless of these differences, gypsy moth (Lymantria dispar L, Lepidoptera: Lymantriidae) performance did not differ when fed American and Chinese chestnuts. We also investigated the effects of jasmonic acid (JA) treatment on differential tannin induction in American and Chinese chestnut leaves and stems. JA treatment increased proanthocyanidins in American chestnut stems and hydrolysable tannins in both tissue types of American chestnut, but did not influence tannin concentrations in Chinese chestnut leaves or stems. HPLC-ESI-MS analysis of pooled samples suggested that hydrolysable tannins in each tissue were qualitatively comprised primarily of ellagitannins, and JA generally increased the number of hydrolysable tannins that could be detected by ESI-MS. Third, we investigated the performance of gypsy moths on JA treated and untreated American and Chinese chestnut. Caterpillar relative growth was not influenced by JA treatment on Chinese chestnut, but decreased in response to JA application on American chestnut. Our results indicate that JA-dependent defenses differ between these chestnut species. This study improves our understanding of ecologically important differences in tannin induction and herbivore susceptibility in Castanea, and has important implications in efforts for American chestnut restoration and commercial chestnut production.     

沼泽红假单胞菌PSB06对辣椒根际微生物群落结构的影响

生物农药的使用极大地减少了对环境的污染,探究生物农药对致病菌的细菌多样性及群落分布将为后续研究生物农药对致病菌的微生态调控提供理论依据.本研究运用Illumina Mi Seq高通量测序技术分析比较辣椒健康植株与疫病发病植株根际土壤微生物多样性,以及研究沼泽红假单胞菌PSB06对植株根际土壤的微生物多样性影响,探究沼泽红假单胞菌PSB06对辣椒疫病的微生态调控机制.结果显示,在第7 d和第14 d的来自同一处理的根际土壤细菌群落多样性变化没有显著差异,辣椒疫病发病植株根际土壤微生物多样性均小于健康植株根际土壤微生物多样性且喷洒沼泽红假单胞菌PSB06发酵液的土样微生物多样性最高;辣椒疫病发病植株根际土壤中放线菌丰度均小于健康植株且喷洒沼泽红假单胞菌菌剂PSB06的土壤中放线菌的丰度最高.辣椒发病植株与健康植株根际土壤中微生物多样性存在显著差异.施用沼泽红假单胞菌可以改善土壤微生物区系,提高土壤微生物群落丰富性以及土壤中放线菌所占的丰度.     

TiO2 photocatalytic antifungal technique for crops diseases control

Introduction N um erous studies have utilized a strong oxidizing pow der of TiO 2 photocatalysts to degrade aqueous or gaseous toxic organic pollutants for w ater purification, w astew ater treatm ent and air pollution control (Fujishim a et al., 2001; K …     

Toxicity of metalaxyl,azoxystrobin, dimethomorph,cymoxanil, zoxamide and mancozeb to Phytophthora infestans isolates from Serbia

A study of the in vitro sensitivity of 12 isolates of Phytophthora infestans to metalaxyl, azoxystrobin, dimethomorph, cymoxanil, zoxamide and mancozeb, was conducted. The isolates derived from infected potato leaves collected at eight different localities in Serbia during 2005–2007. The widest range of EC₅₀ values for mycelial growth of the isolates was recorded for metalaxyl. They varied from 0.3 to 3.9 μg mL^?1 and were higher than those expected in a susceptible population of P. infestans. The EC₅₀ values of the isolates were 0.16–0.30 μg mL^?1 for dimethomorph, 0.27–0.57 μg mL^?1 for cymoxanil, 0.0026–0.0049 μg mL^?1 for zoxamide and 2.9–5.0 μg mL^?1 for mancozeb. The results indicated that according to effective concentration (EC₅₀) the 12 isolates of P. infestans were sensitive to azoxystrobin (0.019–0.074 μg mL^?1), and intermediate resistant to metalaxyl, dimethomorph and cymoxanil. According to resistance factor, all P. infestans isolates were sensitive to dimethomorph, cymoxanil, mancozeb and zoxamide, 58.3% of isolates were sensitive to azoxystrobin and 50% to metalaxyl. Gout's scale indicated that 41.7% isolates were moderately sensitive to azoxystrobin and 50% to metalaxyl.     

High-performance liquid chromatography (HPLC) as a tool for monitoring the fate of fluazinam in soil

Fluazinam is a widely used pesticide employed against the fungal disease late blight in potato cultivation. A specific, repeatable, and rapid high-performance liquid chromatography (HPLC) method utilizing a diode array detector (DAD) was developed to determine the presence of fluazinam in soil. The method consists of acetonitrile (ACN) extraction, clean-up with solid-phase extraction (SPE), and separation using a mobile phase consisting of 70% ACN and 30% water (v/v), including 0.02% acetic acid. HPLC was performed with a C18 column and the detection wavelength was 240 nm. The method was successfully applied to an incubation experiment and to soil samples taken from potato fields where fluazinam had been applied two to three times during the on-going growing season. In the 90-day incubation experiment, analytical standard fluazinam and the commercial fungicide Shirlan^® were added to soil samples that had never been treated with fluazinam, and were then extracted with ACN and 0.01 M calcium chloride (CaCl₂). Fluazinam was not extractable with CaCl₂, indicating that it does not leach to watercourses in the dissolved form. Recovery with ACN extraction for sandy soils was 72–95% immediately after application and 53–73% after 90 days of incubation. Out of the eight potato field soil samples, fluazinam was found in two samples at concentrations of 2.1 mg kg^?1 and 1.9 mg kg^?1, well above the limit of quantification (0.1 mg kg^?1).     

西南水稻白叶枯病菌致病型多样性的垂直分布格局及成因探讨

利用6个含有单抗基因的近等基因系材料为鉴别品种,在水稻的孕穗期采用剪叶接种的方法,测定了西南不同海拔稻区218株水稻白叶枯病菌（Xanthomonas oryzae pv.oryzae）的致病型。结果表明,（1）西南稻区水稻白叶枯病菌致病型具有丰富的多样性,共包含18种,其中9种新致病型为西南地区特有的类型。（2）不同海拔稻区病菌致病型组成存在明显差异,中海拔稻区病菌致病型数量最多,高海拔稻区次之,低海拔稻区最少。低海拔稻区病菌致病型多样性指数、均匀度指数均最低,并且与中海拔和高海拔稻区差异显著。（3）通过分析病菌对抗性基因的克服数量以及鉴别品种病斑长度,表明不同海拔稻区病菌毒力存在明显差异。病菌的毒力与其地理来源的海拔高度呈负相关关系。（4）聚类分析结果显示,以致病型彼此间相似率60%为界,18种致病型可归为4个聚类簇,其中簇Ⅰ毒性最弱,主要集中了高海拔稻区的菌株,簇Ⅳ毒性最强,集中的主要是低海拔菌株。（5）相关性分析表明,病菌致病型多样性特征值与气候类型和寄主品种的多样性呈线性相关关系,气候类型和寄主品种影响病菌致病型的多样性分布,并且寄主品种对病菌的影响程度高于气候类型。就品种的布局而言,低海拔稻区应尽可能使用含有多个抗性基因的聚合品种,而在中、高海拔稻区,应制定好抗性基因轮换的宏观计划,减少低海拔地区向海拔较高的地区稻种的频繁调运,降低水稻白叶枯病的危害。     

Persistence of fluazinam in soil under boreal conditions

Abstract

Fluazinam, a widely used pesticide in conventional potato cultivation, is effective against epidemics of the fungal disease late blight. To assess fluazinam persistence in soil, laboratory experiments were conducted with fluazinam added to soil as a pure chemical or contained in the commercial product Shirlan^®. In a follow-up experiment, the persistence was monitored under constant temperature and water content conditions during a maximum period of 1?year. In an annual climatic rotation experiment, fluazinam added to soil was exposed to the year-round temperature and water content conditions occurring in the boreal zone. A third experiment was undertaken to clarify the effect of soil organic matter (SOM) on the recovery of fluazinam. In the follow-up and annual climatic rotation experiments, more than half of the added fluazinam was recovered after 1?year of incubation. The estimated half-life of fluazinam ranged between 355 and 833?days. The degradation of fluazinam was enhanced by an abundance of SOM, a warm temperature, and wetness. Additionally, in over half of soil samples collected from fields where potato had been intensively cultivated for many years, varying concentrations of fluazinam were detected. Fluazinam can carry over to the next growing season in professional potato production.