5种药剂对2株立枯丝核菌的室内毒力测定

采用生长速率法,在室内测定了w=25%丙环唑、w=12.5%戊唑醇、w=80%乙蒜素、w=25%咪鲜胺和w=5%井冈霉素5种杀菌剂对R-HKB和R-DZC两株立枯丝核菌(Rhizoctonia solani)的毒力。结果表明:丙环唑对R-HKB的毒力和戊唑醇对R-DZC的毒力均最大,其EC50值分别为0.0132mg·L-1和0.4131mg·L-1;井冈霉素对R-HKB和R-DZC的毒力均最小,其EC50值分别为714.4948mg·L-1和663.4171mg·L-1。其毒力倍数分别比丙环唑和戊唑醇小(54128.4倍和1606.0倍)。提示:丙环唑和戊唑醇对R-HKB和R-DZC两株立枯丝核菌有很好的抑制效果。     

Short- and long-term effects of heavy metals on phosphatase activity in soils: An ecological dose-response model approach

Summary The aim of this study was to provide manageable data to help establish permissible limits for the pollution of soil by heavy metals. Therefore the short-and long-term effects of heavy metal pollution on phosphatase activity was studied in five different soil types. The results are presented graphically as logistic dose-response curves. It was possible to construct a curve for sand and silty loam soil but it was more difficult to establish a curve for sandy loam and clay soil and nearly impossible (except for Cu) for peat. The toxicity of the various metals can be compared on the basis of mmol values. In clay soils, for Cd, Cr, Cu, and Zn, the 50% effective ecological dose (ED₅₀) values were comparable (approximately 45 mmol kg^–1), but the ED₁₀ values were very different, at 7.4, 41.4, 15.1, and 0.55, respectively. At the ED₅₀ value, toxicity did not decrease with time and, in sandy soils, was approximately 2.6 mmol kg ^–1 dry soil for Cd, Cu, and Zn. In four out of five soils, the Cd toxicity was higher 1.5 years after the addition of heavy metal salts than after 6 weeks. Toxicity was least in the sandy loam, silty loam, and clay soil, and varied in general between 12 and 88 mmol kg^–1. In setting limits, the criteria selected (no-effect level, ED₁₀ or ED₅₀) determine the concentration and also the toxicity of the sequence. It is suggested that the data presented here could be very useful in helping to set permissible limits for heavy metal soil pollution.     

Promotion of the seed germination and seedling growth of cabbage by root-colonizing fungi isolated from oat and Eucalyptus roots

(Jpn. J. Soil Sci.Plant Nutr., 77, 257–263, 2006)
The symptom of blighted leaves was observed for the melon plants grown on an isolated soil bed after steam sterilization (SS) in a greenhouse in Kochi Prefecture, Japan. To clarify the causes of this symptom, soil and plant analyses were conducted in the first experiment. Manganese concentrations in the leaves with the symptom were higher than 1,000 mg kg−1and exchangeable Mn in the soil was higher than 30 mg kg−1, which indicated the observed symptom was due to Mn excess. In the second experiment, formation of Mn oxide-dissolving substances after SS was examined for several organic amendments, because large amounts of palm chips had been supplied to the soil before SS in the first experiment. As a treatment similar to SS, palm chips, bark compost, and cattle feces manure were autoclaved. The water extracts were collected before and after the autoclave treatment and the Mn oxide-dissolving capacities of the extracts were evaluated. The Mn oxide-dissolving capacity of the water extracts after SS was remarkably higher than before SS, and the value was highest in palm chips, and followed by bark compost, and cattle feces manure. Fractionation and HPLC analysis of the water extracts after SS revealed that the main substance behind Mn oxide reduction in palm tips was arabinose and that in bark manure was malic acid. Further, Mn oxide-dissolving capacities of the water extracts were almost completely explained by the amounts of arabinose or malic acid found in these materials. From these results, it was considered that reducing substances such as arabinose were released by SS from the palm chips which had been applied in large quantity before SS and these reducing substances dissolved the soil Mn oxides and increased the amounts of available Mn, which led to the occurrence of Mn toxicity to the plants.     

Brenneria spp. and Rahnella victoriana associated with acute oak decline symptoms on oak and hornbeam in Iran

Decline diseases of forest trees are complex syndromes not attributable to single causal factors. In Iran, symptoms of decline disease have been observed in a number of native forest species including Quercus castaneifolia (chestnut‐leaved oak), Q. brantii (Persian oak) and Carpinus betulus (hornbeam). The symptoms are prevalent in the northern forests and the Zagros mountain forests. There are parallels between the disease in Iran and acute oak decline (AOD) reported in the UK, specifically the presence of weeping cankers, which have been attributed to a polybacterial complex wherein Brenneria goodwinii is considered a key necrogen. Based on the AOD symptomatology, and as a first step towards discovering potential causal agents of the stem weeping symptoms of affected trees in Iran, necrotic tissues were tested primarily for the presence of B. goodwinii. Symptomatic Q. castaneifolia and C. betulus from the Mazandaran Province and symptomatic Q. brantii from Kohgiluyeh and Boyerahmad Province were sampled. Isolation and culture on a selective medium yielded uniform bacterial colonies. Isolates were characterized using phenotypic and genotypic (DNA sequencing) tests. The isolates were phenotypically identical to members of Pectobacteriaceae and Yersiniaceae, specifically Brenneria and Rahnella spp. The nucleotide sequences of the 16S rRNA and housekeeping genes gyrB, infB and atpD (MLSA) amplified via PCR demonstrated that the isolates from the trees in Iran were indeed B. goodwinii, B. roseae subsp. roseae, Rahnella victoriana and an unknown species of Brenneria. Most bacteria isolated from non‐symptomatic trees were Gram‐positive, and Pseudomonas spp. were dominant, but bacterial species isolated from the diseased trees were not detected in healthy trees. Hypersensitivity response tests were positive, but inoculation on saplings was more variable with internal necrosis developing only once in the test period. Therefore, further testing is required. This is the first report of the incidence of B. goodwinii, B. roseae subsp. roseae, R. victoriana and Brenneria sp. associated with acute oak decline‐like symptoms on Q. castaneifolia, Q. brantii and C. betulus across the western forests of Iran and in the world.     

林木对铝的耐性机理研究进展

在酸性土壤中,铝对林木的毒害是限制林木生长、降低林木生产力、进而导致森林退化的主要因素之一。目前,国内外在林木铝毒害及耐铝机制方面已有较多的研究,但关于林木耐铝的生理和分子机制的综述性报道很少。文中综述了近年来林木对铝的富集、铝对林木生理和分子水平上的毒害等方面的研究进展,总结了林木耐铝的生理机制和分子机制,简要介绍了外源添加物对林木耐铝毒的调控机制,提出了今后有关林木铝毒需进一步研究的重点,以期为林木铝毒的深入研究提供参考以及为缓解我国酸性土壤林木铝毒害及森林的健康持续经营提供参考。     

水体常见喹诺酮类抗生素对发光菌的毒性作用

以明亮发光杆菌(Photobacterium phosphoreum)为受试生物,研究3种水体常见的喹诺酮类抗生素(QNs)对其的单一毒性和联合毒性作用,并基于毒性单位法、相加指数法和混合毒性指数法等联合作用评价方法,对混合体系的联合毒性作用类型进行分析。结果表明,不同的评价方法对3种QNs的联合效应评价结果具有较好的一致性,联合毒性作用类型均表现为不同程度的拮抗作用。根据发光菌发光原理和QNs分子结构不同,可对联合毒性作用的机理进行初步探讨。多种QNs混合体系的联合毒性作用呈现出以拮抗效应为主,揭示了此类医药品在环境中联合使用时可导致药效的降低或引发微生物耐药性的传播。     

马铃薯干腐病室内药剂筛选及防病研究

采用生长速率法测定了咯菌腈、苯醚甲环唑、咪鲜胺、戊唑醇、氰烯菌酯和恶霉灵6种杀菌剂对4种马铃薯干腐病菌的室内毒力。结果表明,不同种类镰刀菌对药剂的敏感性存在差异。对4种镰刀菌抑制作用最强的药剂均为咪鲜胺,EC_(50)值范围为0.010~0.057μg/m L;氰烯菌酯对接骨木镰刀菌菌丝生长无抑制作用;而恶霉灵的抑菌作用普遍较差,EC_(50)值为9.340~64.408μg/m L;其他4种药剂效果较好。对接菌薯块进行药剂处理可抑制病斑横向扩展及病原菌纵向侵入,但不同杀菌剂防效不同。苯醚甲环唑、咪鲜胺和戊唑醇效果较佳。     

九种杀虫剂防治苏铁小灰蝶的药效试验

为了筛选控制苏铁小灰蝶(Chilades pandava)的有效药剂,通过室内毒力测定和田间药效试验研究9种杀虫剂对苏铁小灰蝶的防治效果。结果表明,48%毒死蜱乳油1 000倍液、90%晶体敌百虫1 000倍液、2%甲维盐(甲氨基阿维菌素苯甲酸盐)微乳剂1 500倍液和20%康宽(氯虫苯甲酰胺)悬浮剂3 000倍液室内施药后72 h对苏铁小灰蝶3龄幼虫的校正死亡率分别达到100.00%、95.00%、93.35%、100.00%,田间施药后1、3、7 d,4种杀虫剂对苏铁小灰蝶的虫口减退率和田间防治效果均在90%以上。其次是2.5%功夫(高效氯氟氰菊酯)微乳剂3 000倍液、2.5%劲彪(高效氯氟氰菊酯)乳油3 000倍液、1.8%阿维菌素乳油1 000倍液、10%除尽(虫螨腈)悬浮剂1 500倍液也表现出良好的杀虫效果,室内施药后72 h,4种杀虫剂对苏铁小灰蝶3龄幼虫的校正死亡率分别达88.35%、80.00%、88.35%、85.00%;田间施药后3、7 d,4种杀虫剂对苏铁小灰蝶的虫口减退率和防治效果均达80%以上;2.5%敌杀死(溴氰菊酯)乳油杀虫效果最差,室内施药后72 h,对苏铁小灰蝶3龄幼虫的校正死亡率为78.35%,田间施药后1、3、7 d,对苏铁小灰蝶的虫口减退率和防治效果均在70%以下。     

Cadmium‐induced changes in glutathione and phenolics of Thlaspi and Noccaea species differing in Cd accumulation

Glutathione (GSH) and phenolics play an important role in plant defense against metal‐ion toxicity. The antioxidant activity and metal‐binding capacity of these compounds can account for the protective effects. In contrast to animal‐cell models, however, the possible interplay among these substances in stress defense of plants is poorly investigated. This study compares the influence of cadmium (Cd) on the profiles of both soluble phenolics and GSH in shoots of different Thlaspi and Noccaea species: two ecotypes of the nonhyperaccumulator T. arvense differing in Cd resistance (ecotype Aigues Vives, Cd‐sensitive, and ecotype Jena, Cd‐resistant) and two Cd‐tolerant Cd‐Zn hyperaccumulators N. praecox and N. caerulescens (formerly Thlaspi praecox and T. caerulescens). To reveal the possible influence of Cd‐induced sulfur (S) shortage on the stress response, plants receiving normal S concentrations (500 μM MgSO₄) and plants treated with surplus S (500 μM MgSO₄ + 500 μM K₂SO₄) were analyzed. Our working hypothesis was that species differences in tolerance to high tissue Cd concentrations should be reflected by differences in endogenous levels of GSH and phenolic compounds. The results reveal clear species‐dependent differences in both the constitutive patterns and the Cd‐ and S‐induced changes in shoot concentrations of GSH and phenolics. However, no simple relationship between these shoot concentrations and Cd accumulation and tolerance can be established.     

Availability of soil boron fractions to M.26 apple rootstock

The availability of various boron (B) fractions in soil to M.26 apple (Malus spp.) rootstock was examined. The study was carried out in a greenhouse on soils with diverse chemical and physical properties. The following B fractions were determined: (i) B in soil solution, (ii) B non‐specifically adsorbed on soil surface, (iii) B specifically adsorbed on soil colloid surfaces, (iv) B occluded in Mn oxyhydroxides, (v) B occluded in noncrystalline aluminum (Al) and iron (Fe) oxides, (vi) B occluded in crystalline Al and Fe oxides, (vii) B fixed with soil silicates, and (viii) total soil B. In the studied soils there were: 0.07–0.17 mg kg^‐1 B in soil solution, 0.01–0.03 mg kg^‐1 B non‐specifically adsorbed on soil surface, 0.04–0.08 mg kg^‐1 B specifically adsorbed on soil colloid surfaces, 0.28–0.67 mg kg^‐1 B occluded in manganese (Mn) oxides, 4.03–17.22 mg kg^‐1 B occluded in noncrystalline Al and Fe oxides, 8.93–50.62 mg kg^‐1 B occluded in crystalline Al and Fe oxides, 12.2–42.5 mg kg^‐1 B fixed with soil silicate, and 52.9–82.2 mg kg^‐1 total B. Simple correlation analysis showed positive correlation between B contents in M.26 apple rootstocks and amounts of B in soil solution (r=0.77), B non‐specifically adsorbed on soil colloid surfaces (r=0.65), B specifically adsorbed on soil surface (r=0.76) and B occluded in Mn oxyhydroxides (r=0.77). No relation was found between plant B contents and amounts of B occluded in non‐crystalline and crystalline Al and Fe oxides, B fixed with soil silicates and total B. The results indicated that extraction of B by 0.1 M NH₂OH HCl solution adequately represented amounts of B in soil solution, B non‐specifically and specifically adsorbed on soil compound surfaces and B occluded in Mn oxyhydroxides to assess availability of B to apple trees.