Predicted impact of transgenic, herbicidetolerant corn on drinking water quality in vulnerable watersheds of the mid-western USA

In the intensely farmed corn-growing regions of the mid-western USA, surface waters have often been contaminated by herbicides, principally as a result of rainfall runoff occurring shortly after application of these to corn and other crops. In some vulnerable watersheds, water quality criteria for chronic human exposure through drinking water are occasionally exceeded. We selected three settings representative of vulnerable corn-region watersheds, and used the PRZM-EXAMS model with the Index Reservoir scenario to predict corn herbicide concentrations in the reservoirs as a function of herbicide properties and use pattern, site characteristics and weather in the watersheds. We compared herbicide application scenarios, including broadcast surface pre-plant atrazine and alachlor applications with a glyphosate pre-plant application, scenarios in which losses of herbicides were mitigated by incorporation or banding, and scenarios in which only glyphosate or glufosinate post-emergent herbicides were used with corn genetically modified to be resistant to them. In the absence of drift, in almost all years a single runoff event dominates the input into the reservoir. As a result, annual average pesticide concentrations are highly correlated with annual maximum daily values. The modeled concentrations were generally higher than those derived from monitoring data, even for no-drift model scenarios. Because of their lower post-emergent application rates and greater soil sorptivity, glyphosate and glufosinate loads in runoff were generally one-fifth to one-tenth those of atrazine and alachlor. These model results indicate that the replacement of pre-emergent corn herbicides with the post-emergent herbicides allowed by genetic modification of crops would dramatically reduce herbicide concentrations in vulnerable watersheds. Given the significantly lower chronic mammalian toxicity of these compounds, and their vulnerability to breakdown in the drinking water treatment process, risks to human populations through drinking water would also be reduced.     

灭生性除草剂草铵膦在抗除草剂转基因早稻栽培中应用效果研究

随着栽培方式的日益简化,草害成了水稻减产的重要因素,笔者以常规除草剂除草方式为对照,研究了转基因抗草铵膦杂交早稻香125S/Bar68-1在直播、抛秧和机插3种栽培方式中草铵膦的应用效果。研究结果表明：在3种栽培方式中,草铵膦除草效果都优于常规除草,尤其在杂草较多的直播田优势更加明显;虽然个别产量相关性状在不同年份存在显著差异,但草铵膦除草剂除草对转基因早稻的实际产量没有显著影响。     

Characteristic analysis of tetra-resistant genetically modified rice

In this study, the characteristic of three transformants named as B1 C106-1, B1 C106-2, and B1 C106-3 were studied that carried three innate resistant genes Bph14, Bph15, and Xa23, and two enthetic resistant genes Cry1 Ca# and Bar. The five resistant genes were all verified by PCR and the two enthetic genes were identified in single copy insertion by Southern blot. At tillering stage, the Cry1 C and PAT(phosphinothricin acetyl transferase) protein contents in leaf, sheath, and stem of T2 generation were in the similar pattern: leafstemsheath, and showed significant difference(P0.01) among three organs. The average contents of Cry1 C protein in plant of B1 C106-1, B1 C106-2, and B1 C106-3 were 12.95, 6.57, and 11.30 μg g–1, respectively, and showed significant difference(P0.01) among them. However, the average contents of PAT in plant of B1 C106-1, B1 C106-2, and B1 C106-3 were 28.54, 27.66, and 28.02 μg g–1, respectively, and there were no significant difference among three transformants. The glufosinate tolerable concentration of three transformants of T3 generation reached at least 6 g L–1, and the mortality of rice leaf rollers were above 97.4% in 5 days after being fed with fresh transformants' leaves. The Cry1 C protein toxicity was also assessed by silkworms, and the mortality of silkworms feeding mulberry leaves smeared with Cry1 C protein extracts of leaves of B1 C106-1, B1 C106-2, and B1 C106-3 were 90, 67.8, and 87.8%, respectively, that were positive correlation(r=0.993) with Cry1 C protein contents in plant of three transformants. The three transformants also maintained high resistance to brown planthopper and bacterial blight as the original version. The above results indicate the tetra-resistant rice germplasm was well-developed by pyramiding innate and enthetic resistant genes in an elite line to provide with resistances of glufosinate, rice leaf roller, brown planthopper, and bacterial blight.     

Metabolism of the herbicide glufosinate‐ammonium in plant cell cultures of transgenic (rhizomania‐resistant) and non‐transgenic sugarbeet (Beta vulgaris), carrot (Daucus carota), purple foxglove (Digitalis purpurea) and thorn apple (Datura stramonium)

The metabolism of the herbicide glufosinate‐ammonium was investigated in heterotrophic cell suspension and callus cultures of transgenic (bar‐gene) and non‐transgenic sugarbeet (Beta vulgaris). Similar studies were performed with suspensions of carrot (Daucus carota), purple foxglove (Digitalis purpurea) and thorn apple (Datura stramonium). ¹⁴C‐labelled chemicals were the (racemic) glufosinate, L ‐glufosinate, and D ‐glufosinate, as well as the metabolites N‐acetyl L ‐glufosinate and 3‐(hydroxymethylphosphinyl)propionic acid (MPP). Cellular absorption was generally low, but depended noticeably on plant species, substance and enantiomer. Portions of non‐extractable residues ranged from 0.1% to 1.2% of applied ¹⁴C. Amounts of soluble metabolites resulting from glufosinate or L ‐glufosinate were between 0.0% and 26.7% of absorbed ¹⁴C in non‐transgenic cultures and 28.2% and 59.9% in transgenic sugarbeet. D ‐Glufosinate, MPP and N‐acetyl L ‐glufosinate proved to be stable. The main metabolite in transgenic sugarbeet was N‐acetyl L ‐glufosinate, besides traces of MPP and 4‐(hydroxymethylphosphinyl)butanoic acid (MPB). In non‐transgenic sugarbeet, glufosinate was transformed to a limited extent to MPP and trace amounts of MPB. In carrot, D stramonium and D purpurea, MPP was also the main product; MPB was identified as a further trace metabolite in D stramonium and D purpurea. © 2001 Society of Chemical Industry     

转phyA2、ZmTMT和Bar玉米的获得及其特性分析

【目的】玉米是家禽和单胃动物饲料的主要原料,但玉米籽粒中高活性的α-生育酚含量较低,且籽粒中的磷主要是以植酸磷的形式存在,动物不能有效吸收利用,因此,饲料中需要添加化学合成的维生素E和无机磷或微生物来源的植酸酶以满足动物生长发育的需要,增加了饲料成本,同时又容易造成磷污染。通过转基因获得α-生育酚含量和植酸酶活性大量提高的玉米,为饲用玉米育种提供材料基础。【方法】构建含有3个基因表达盒的载体,采用农杆菌侵染的方法转化玉米,草铵膦作为筛选压力;通过喷施草铵膦和PCR鉴定的方法筛选转基因阳性植株,RT-PCR分析目的基因在转录水平的表达情况;Western blot分析目的基因在翻译水平上的表达情况,采用分光光度计测定转基因玉米籽粒中的植酸酶活性,利用HPLC测定籽粒中的维生素E含量,同时比较转基因株系与野生型在其他营养成分和农艺性状上的差异。【结果】构建了胚乳特异性启动子123387驱动的植酸酶基因phyA2表达盒、胚特异性启动子13387驱动的玉米γ-生育酚甲基转移酶基因ZmTMT表达盒以及组成型启动子CaMV 35S驱动的草铵膦抗性基因Bar表达盒串联的植物表达载体;转化玉米获得转基因植株;喷施草铵膦和PCR鉴定得到阳性植株;经过多个世代回交转育,获得目标性状均较好的2个转基因纯合玉米株系TPB1和TPB2;RT-PCR和Western blot分析结果表明phyA2、ZmTMT和Bar在转基因玉米中显著高表达。植酸酶活性测定结果表明,转基因玉米籽粒中植酸酶活性达到10 000—13 000 U·kg^-1。维生素E含量测定结果表明,转基因玉米籽粒中90%以上的γ-生育酚转化为α-生育酚,α-生育酚的含量达到50—70 mg·kg^-1,α-三烯生育酚的含量也有明显增加。转基因玉米中的植酸酶活性和α-生育酚含量完全能够满足动物饲料的需要。转基因株系的农艺性状与野生型无显著差异,TPB1的营养成分与野生型总体无显著差异,TPB2稍高于野生型但是未产生不利影响;且均具有草铵膦抗性。【结论】获得的富含维生素E和植酸酶、且具有除草剂抗性的玉米新材料可以用于玉米杂交种的开发应用,降低饲料成本,提高磷的利用率,减少环境污染。     

Effects of relative humidity and substrate on the spatial association between glyphosate and ethoxylated seed oil adjuvants in the dried deposits of sessile droplets

BACKGROUND: In recent years, several studies have shown the impact of adjuvants on the characteristics of herbicide deposits on leaf surfaces. Until now, most studies have addressed the distribution of active ingredients (AIs), whereas few experiments have focused on the location of the adjuvants. The objective of this study was a systematic examination of the particle distribution profile of both the AI (glyphosate, Gly) and the adjuvants after the application of sessile microdroplets on hydrophobic (Teflon) and hydrophilic (glass and aluminium) model surfaces. RESULTS: The association degree (AD) was surface dependent and specific for the tested adjuvants. In general, the rather hydrophobic adjuvant RSO 5 showed decreasing AD with Gly at increasing relative humidity (RH) levels. The rather hydrophilic RSO 60 adjuvant displayed higher AD between the compounds at a higher RH. A high concentration of the adjuvant reduced the AD for both of the RSO adjuvants evaluated. CONCLUSION: The combination of surface properties, the type of adjuvant and the relative humidity determines the degree of association between Gly and the adjuvants. The present results suggest that the interaction between the AI and an adjuvant determines whether spatial separation occurs, whereas physical processes (e.g. capillary particle movement, inward and outward Marangoni flows and the evaporation rate) are decisive for the extent of the separation. Coffee‐ring structures were formed exclusively with the adjuvant + Gly mixtures, whereas Gly alone formed either one big deposit or several small islands distributed within the droplet footprint. Copyright © 2011 Society of Chemical Industry     

Efficacy of four corn (Zea mays L.) herbicides when applied with flat fan and air induction nozzles

Twelve field experiments were conducted over a 4 year (2002–2005) period to determine the influence of the herbicide dose, nozzle type, spray volume, and spray pressure on herbicide efficacy in field corn ( Zea mays L.). The control of Abutilon theophrasti (velvetleaf ), Ambrosia artemisiifolia (common ragweed), Chenopodium album (common lambsquarters), Amaranthus powellii (green pigweed), and Echinochloa crus-galli (barnyard grass) was improved with the use of full herbicide doses compared to half doses of bromoxynil, glufosinate, dicamba, and nicosulfuron. The yield was increased for bromoxynil, glufosinate, and nicosulfuron when the full herbicide dose was used. When applied at the manufacturer's recommended dose, flat fan nozzles, compared to air induction (AI) nozzles, provided better control of A. theophrasti , A. artemisiifolia , and C. album with bromoxynil, A. artemisiifolia and C. album with dicamba, and E. crus-galli with nicosulfuron. Bromoxynil, in relation to weed control, was the only herbicide that was affected by the water carrier volume. By increasing the spray pressure with an AI nozzle, there was an improvement in the control of A. theophrasti , A. artemisiifolia, and C. album with the application of bromoxynil and E. crus-galli with the application of nicosulfuron, with a yield increase with bromoxynil. Overall, this study concludes that the optimum nozzle type, water carrier volume, and spray pressure is herbicide- and weed species-specific.     

The glutamate dehydrogenase gene gdhA increased the resistance of tobacco to glufosinate

The gene gdhA from Escherichia coli, that encodes a NADPH‐dependent glutamate dehydrogenase (GDH), directs a novel pathway in transgenic plants that allows an increase in ammonium assimilation. Glufosinate leads to plant death by the irreversible inhibition of glutamate synthetase (GS) leading to a disruption of subsequent GS‐related processes resulting in elevated ammonium and disruption of photorespiration. Therefore, it was speculated that the gdhA‐transformed plants may exhibit a novel mechanism of resistance to glufosinate by altered activity of the GDH‐directed pathway(s) and subsequently related processes. Studies were conducted in the greenhouse to evaluate the resistance of tobacco plants containing the gdhA gene to glufosinate. Five tobacco genotype lines were investigated including a non‐transformed control line, a positive control line and three transformed lines with levels of increasing GDH activity directed by the gdhA gene. Plants transformed with the gdhA gene expressed up to six times increased level of resistance (GR₅₀) to glufosinate compared with the non‐transformed control, which is 100 times less resistant than plants transformed with the bar gene. The GDH activity among lines was highly correlated (r² = 0.9903) with the level of herbicide resistance. Thus, the use of the E. coli gdhA gene in plant transformations can provide an additional mechanism for resistance to glufosinate.