蜈蚣草对砷锑镉的富集效果及体内存在形态研究

【目的】探究在水培条件下,蜈蚣草受到 As、Sb、Cd 单一胁迫及交互胁迫后,对其富集特征及体 内的赋存形态变化。【方法】选用重金属耐受植物蜈蚣草为载体,利用改良霍格兰营养液水培 7 d,通过不同梯度 As、Sb、Cd 胁迫探究富集特征,并探究浓度为 50 mg/L 时不同处理条件下 As、Sb、Cd 在蜈蚣草中的赋存形态特征。 【结果】重金属单一胁迫下,蜈蚣草地下部 As、Sb、Cd 富集浓度最大值分别为 337.56、7 020.90、2 742.58 mg/kg, 地上部最大富集浓度分别为 886.60、3 058.60、4 045.80 mg/kg,蜈蚣草仅对 As 的转移系数稳定＞ 1;在浓度 50 mg/L 下,单一胁迫或交互胁迫时,蜈蚣草体内 As 乙醇态与盐酸态浓度占比为 69.49%~94.25%,Sb 残渣态浓度占比为 47.48%~78.36%,Cd 盐酸态浓度占比为 93.67%~98.46%;加入 Sb 后,蜈蚣草地下部、地上部对 As 的吸附浓度分别 提高 60.83、144.40 mg/kg,As、Cd 的加入能大幅降低蜈蚣草根、茎、叶中 Sb 乙醇态浓度,降幅为 72.9%~97.0%, As、Sb 的加入会促进蜈蚣草根部 Cd 盐酸态浓度,升幅达 38.2%~206.5%。【结论】蜈蚣草对 Sb、Cd 的富集能力较 强,但仅为高富集作用。在胁迫浓度 50 mg/L 下,蜈蚣草体内 As 以乙醇提取态与盐酸提取态为主,Sb 以残渣态为主, Cd 以盐酸提取态为主,Sb 可以提高蜈蚣草对 As 的富集能力,As、Cd 对 Sb 毒性具有拮抗作用,As、Sb 对蜈蚣草 根部 Cd 盐酸态有促进作用,蜈蚣草对 As、Sb 复合污染的土壤具有更好的修复能力。     

水稻纹枯病拮抗细菌分离与鉴定

对从水稻纹枯病稻田土壤中分离筛选的176株细菌进行抑菌率比较,并对其进行鉴定,以期为水稻纹枯病的生物防治提供理论依据.结果表明:SR32菌株抑菌带为16.4 mm,抑菌率为73.6%,根据形态学和生理生化特征初步鉴定为枯草芽孢杆菌(Bacillus subtilis).     

长白山地区不同海拔环境拮抗放线菌的筛选

利用稀释平板倾注法从吉林长白山地区不同海拔高度的不同环境中共分离到各种放线菌菌株104株.以24种农业常见植物致病真菌作为目标供试菌,采用抑制菌丝生长速率法对104株放线菌进行抗菌活性筛选,优选抗菌活性较佳的12株.将最佳放线菌No.6菌株进行液体发酵,并测定其发酵液滤液的抑菌活性.结果表明,No.6放线菌菌株对香蕉灰纹菌、辣椒疫霉菌、黄瓜炭疽菌、番茄灰霉菌、黄瓜黑星菌、番茄叶霉菌、番茄炭疽菌、棉花黄萎菌、黄瓜枯萎菌、小麦赤霉菌、稻曲病菌、水稻恶苗病菌、小麦纹枯病菌、水稻稻瘟病菌、水稻纹枯菌、油菜菌核菌均具有优异的防治效果,发酵滤液稀释10倍后对黄瓜黑星菌、番茄炭疽菌、稻曲病菌、水稻稻瘟病菌、水稻纹枯菌的抑制率分别达90.0%、93.3%、92.0%、93.3%、92.0%.     

假单胞菌对香蕉枯萎病菌的抑制作用

从已感染香蕉枯萎病的果园中分离到1株对香蕉枯萎病菌（Fusarium oxysporum f.sp.cubense）抑制作用很好的菌种,命名为G1。采用固体和液体培养法从不同角度证实了G1对香蕉枯萎病菌生长的抑制作用。结果表明,G1的发酵液、无菌滤液、挥发性物质、非挥发性代谢产物的平均抑菌率分别为92.5%、27.4%、73.8%、57.7%,可见抑制作用与活菌体有直接关系,其中产生挥发性物质尤其重要。液体培养的病原菌浓度为1.0×107cfu/mL经G1作用10d后,取样镜检发现G1通过抑制病原菌菌丝正常生长以至不能产孢,从而导致菌丝消融;通过吸附在孢子的周围,融解细胞壁,造成原生质泄露致使孢子死亡。     

香蕉枯萎病生防细菌的筛选、鉴定及其抑菌作用

采用平板对峙法,从香蕉根部土样中分离到1株枯萎病拮抗芽孢杆菌XY-10。根据形态特征及16S rDNA分析将其鉴定为多粘类芽孢杆菌Paenibacillus polymyxa。拮抗试验表明菌株XY-10不同浓度的发酵滤液均可抑制病原菌孢子萌发和生长,当发酵滤液浓度分别为10%、30%和50%时,其在高度抑制水平上的抑制率分别为7%、23%和40%。经发酵滤液处理,病原菌菌丝末端膨大成球状、菌丝破裂、消解,菌丝体分枝增多。     

蜜蜂患白垩病虫体内一株球囊菌拮抗细菌的分离与鉴定

【目的】寻找抑制蜜蜂球囊菌的拮抗菌,用于白垩病的生物防治。【方法】利用细菌纯化技术从患白垩病的蜜蜂幼虫体内分离纯化了一株对蜜蜂球囊菌(Ascosphaera apis)有抑制作用的细菌,并结合形态学、革兰氏染色以及16S rDNA序列分析技术进行鉴定,同时通过蜜蜂体内、体外接种试验研究其对蜜蜂球囊菌的抑制作用。【结果】该细菌被初步鉴定为蜡样芽胞杆菌(Bacillus cereus),它在培养基中能够完全抑制蜜蜂球囊菌的生长,但其发酵液对蜜蜂球囊菌的生长没有影响。将含菌饲料喂蜜蜂幼虫,蜜蜂幼虫的死亡率和生长发育没有受到影响,说明该细菌对蜜蜂幼虫没有致病性。蜜蜂幼虫体内同时接种细菌和球囊菌孢子,发现细菌对球囊菌在蜜蜂体内的萌发和初期菌丝的生长没有影响,蜜蜂依然能够患病,但生长后期该细菌能够降解球囊菌菌丝,对球囊菌子代孢子的产生表现出一定的抑制作用。【结论】 该研究结果为蜜蜂白垩病的生物防治提供了理论依据。     

Control of rice sheath blight by phyllosphere epiphytic microbial antagonists

Epiphytic microorganisms on the phyllosphere of traditional and high-yielding rice varieties were isolated from different agroecological zones of Sri Lanka and screened for theirin vitro andin vivo antagonism againstRhizoctonia solani Kühn AG-1 1A, the sheath blight pathogen of rice. Among a total of 196 bacterial and 91 fungal isolates, 12 bacterial and two fungal isolates which showed more than 50% growth inhibition ofR. solani were tested for theirin vivo antagonism. Among the 14 antagonists tested, six bacterial and one fungal isolate substantially reduced the incidence of sheath blight (by more than 82%) and severity (by more than 92%) of the rice varieties BG94-1 and IR8 grown in a pot experiment under open field conditions. Using five antagonists that showed the bestin vitro antagonism, a pot experiment was conducted to determine whether the presence of indigenous microflora on the rice sheath had any effect on the effectiveness of antagonism. Three isolates (B4, GbB5 and HMWB4) controlled sheath blight incidence and severity equally well in the presence and absence of indigenous microflora. Two isolates (BG352B1 and BG300B1) were more effective when they were introduced into the rice sheath without indigenous microflora. Among the effective antagonists determined by the pot experiment, isolates B4, B16, BG94-1B5, GbB5, HMWB4 and BG379-F2 were tested under field conditions for two consecutive growing seasons. Under field conditions, severity of rice sheath blight was significantly reduced by the application of all the tested antagonists as a spray on rice sheath at a concentration of 10⁸ cfu ml⁻¹, starting 3 days after the development of symptoms and continuing for three applications at 10-day intervals. Antagonistic performances were consistent in the two seasons under field conditions andB. megatarium A (isolate B16) andAspergillus niger (isolate BG379-F2) performed as the most effective antagonists in both seasons. When disease severity was quantified as percentage sheath area covered by the disease lesions, the respective reductions in disease severity were greater than 50% and 61% byB. megaterium A (isolate B16) andAspergillus niger (isolate BG379-F2), respectively, in both seasons. http://www.phytoparasitica.org posting Jan. 10, 2008.     

Effects of Cry1Ac toxin of Bacillus thuringiensis and nuclear polyhedrosis virus of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) on larval mortality and pupation

In the laboratory, the percentage mortality and pupation of Helicoverpa armigera (Hübner) were investigated when larvae were exposed to Cry1Ac of Bacillus thuringiensis Berliner, nuclear polyhedrosis virus of H. armigera (HaNPV) or Cry1Ac and HaNPV together. The results revealed that interactions between Cry1Ac and HaNPV varied with bioassay method and concentration of the suspension. When larvae were infected using a suspension containing both HaNPV and Cry1Ac, most combinations of Cry1Ac (62.5, 125 and 250 microg mL(-1)) and HaNPV (1.2 x 10(6), 6.0 x 10(6) and 3.0 x 10(7) PIB mL(-1)) showed an antagonistic effect. In the bioassay procedure where larvae were force fed diet containing Cry1Ac 48 h after being infected by HaNPV, interaction between Cry1Ac (0.5, 1, 2, 4 and 8 microg mL(-1)) and HaNPV (6.0 x 10(6) and 3.0 x 10(7) PIB mL(-1)) showed an additive effect, while combinations of Cry1Ac (0.5, 1, 2 and 4 microg mL(-1)) and HaNPV (1.2 x 10(6) PIB mL(-1)) showed an antagonistic effect. In the bioassay procedure where larvae being infected by HaNPV were fed on Cry1Ac diet from neonate to death or pupation, the results suggested that Cry1Ac and HaNPV showed an additive interaction. The percentage mortality was lower in the treatment of larvae infected by transgenic Bt cotton leaf discs containing HaNPV suspension than in the treatment of larvae by conventional cotton leaf discs containing HaNPV, while the pupation rate was higher. The combination of Bt cotton and HaNPV showed antagonism. The present results showed that a combination of Cry1Ac and HaNPV usually resulted in mortality levels greater than in the case of Cry1Ac but not greater than with the virus alone.     

海南省土壤拮抗放线菌分离方法初探

针对海南土样拮抗放线菌的分离,实验初步解决了土样中的细菌和真菌在放线菌分离培养中的污染问题。研究测定了细菌和真菌抑制剂K2Cr2O7的最佳使用浓度、土样稀释浓度、土样加热和风干处理以及土样的贮存时间等对放线菌分离培养的影响。结果表明：K2Cr2O7在一定的浓度范围内使用可以明显抑制细菌的生长,对放线菌的生长无明显的影响,浓度在50μg／ml时效果最佳。当K2Cr2O7 的使用浓度在70μg／ml时放线菌生长受到抑制,使用浓度在30μg／ml时对细菌的抑制效果不明显;土样溶液涂抹平板培养时,土样溶液浓度在10-3~10-4时平板内长出的菌落在30~40个间,菌落的重叠率在20%左右,分离效率较高,是理想的浓度;在土样放置一个星期的自然风干后,同时使用细菌抑制剂K2Cr2O7可得到较理想的培养效果;对土样进行加热处理后,可明显降低细菌的数量,但同时也会降低放线菌数量,分离效率过低。     

Efficacy of insecticide mixtures against larvae of Culex quinquefasciatus (Say) (Diptera: Culicidae) resistant to pyrethroids and carbamates

The efficacy of insecticide mixtures of permethrin (pyrethroid) and propoxur (carbamate) was tested by larval bioassays on two strains of Culex quinquefasciatus (Say), one resistant to pyrethroids and the other resistant to carbamates. The method consisted in combining one insecticide at the highest concentration causing no mortality (LC0) with increasing concentrations of the second one. The concentration-mortality regression lines were determined for permethrin and propoxur alone and in combination, and synergism ratios (SR) were calculated in order to determine the magnitude of an increase or decrease in efficacy with use of the mixtures. With the pyrethroid-resistant strain (BK-PER), the results showed that propoxur at LC0 significantly enhanced the insecticidal activity of permethrin (SR50 = 1.54), especially on the upper range of the concentration-mortality regression. Conversely, when permethrin at LC0 was tested with propoxur against the carbamate resistant strain (R-LAB), an antagonistic effect was observed (SR50 = 0.67). With the BK-PER strain, an increased oxidative detoxification (MFO) appeared to be the main mechanism responsible for the synergistic interaction. Nevertheless, antagonism in the R-LAB strain is probably due to a physiological perturbation implying different target sites for pyrethroid (ie sodium channel) and carbamate insecticides [ie acetylcholinesterase (EC 3.3.3.7) and choline acetyltransferase (EC 2.3.1.6)].