Influence of Metalaxyl on Three Nematodes of Citrus

Metalaxyl significantly reduced population of Pratylenchus coffeae, Radopholus similis, and Tylenchulus semipenetrans in roots of Citrus limon (rough lemon) under greenhouse conditions. Postinoculation treatment of rough lemon seedlings was not as effective i n reducing nematode populations as was treatment before inoculation. Fewer nematodes infected metalaxyl-treated roots than nontreated roots. However, incubation of nematodes in metalaxyl did not inhibit nematode motility or their ability to locate and infect roots. Cellular responses to nematode injection differed between treated and nontreated tissues. Metalaxyl appeared to confer nematode contraol by modifying citrus roots such that a normally susceptible rootstock became tolerant.     

Preplant Fumigation for Citrus Nematode Control in Florida

Preplant soil fumigation experiments were conducted to control the citrus nematode, Tylenchulus semipenetrans. Generally, D-D (1,3-dichloropropene, 1,2-dichloroptopane and related chlorinated C₃-hydrocarbons), Telone (1,3-dichloropropene and related chlorinated C₃-hydrocarbons), Telone PBC (80% 1,3-dichloropropene, 15% chloropicrin, 5% propargyl bromide), and EDB (ethylene dibromide) controlled T. semipenetrans effectively for 4 years. The trials involved four scion varieties, two rootstock varieties and three soil types. Tree growth and yield were increased with application of D-D at 374 or 561 liters/ha (40 or 60 gal/acre) or Telone at 299 or 449 liters/ha (32 or 48 gal/acre) in broadcast and strip treatments.     

Comparison of Millet and Sorghum-Sudangrass Hybrids Grown in Untreated Soil and Soil Treated with Two Nematicides

Aldicarb and Bay 68138 (ethyl 4-(methylthio)-m-tolyl isopropylphosphoramidate) were effective in increasing the plant height and yield of millet and sorghum-sudangrass hybrids. Stunting of plants and reduction in yield were inversely proportional to the number of Pratylenchus spp. and Belonolaimus longicaudatus present in the rhizosphere. Millet and sorghum-sudangrass hybrids supported large numbers of Criconemoides ornatus, Pratylenchus spp., B. longicaudatus, and Xiphinema americanum. Funk''s sorghum × sudangrass Hybrid 78 was more sensitive to injury by the nematode complex than were Tift 23A × 186 or Gahi-I pearl millet. ''Tiflate'' pearl millet was more resistant than other millets or sorghums to injury caused by C. ornatus, Pratylenchus spp., Trichodorus christiei, and B. longicaudatus. Millet and sorghum-sudangrass hybrids are poor summer cover crops because they favor intensive development of P. brachyurus, P. zeae, T. christiei, and B. longicaudatus.     

Growth of Potato and Control of Pratylenchus penetrans with Oxamyl-treated Seed Pieces in Greenhouse Studies

Oxamyl was applied to both uncut and cut potato tubers in aqueous solutions of 1,000 to 32,000 μg/ml. Emergence in greenhouse pots was delayed for a day or more after soaking cut tuber pieces in 32,000 μg/ml. After 10 weeks plant growth was greater, relative to the control, when Pratylenchus penetrans-infested soil was planted with cut tubers soaked for 20 minutes in 32,000 μg/ml. Soaking for 40 minutes did not increase nematode control nor affect plant growth. Oxamyl applied to tubers at 1,000 μg/ml reduced the numbers of P. penetrans in the soil by 20% and in the roots by 35%; at 32,000 μg/ml, the numbers of P. penetrans in the soil were reduced by 73-86% and in the roots by 86-97%. The numbers of P. penetrans did not increase in the roots of plants developed from cut tubers soaked in 32,000 μg/ml over a period of 10 weeks, but numbers of lesion nematodes had begun to increase in the soil.     

Mimetic host shifts in an endangered social parasite of ants

An emerging problem in conservation is whether listed morpho-species with broad distributions, yet specialized lifestyles, consist of more than one cryptic species or functionally distinct forms that have different ecological requirements. We describe extreme regional divergence within an iconic endangered butterfly, whose socially parasitic young stages use non-visual, non-tactile cues to infiltrate and supplant the brood in ant societies. Although indistinguishable morphologically or when using current mitochondrial and nuclear sequence-, or microsatellite data, Maculinea rebeli from Spain and southeast Poland exploit different Myrmica ant species and experience 100 per cent mortality with each other''s hosts. This reflects major differences in the hydrocarbons synthesized from each region by the larvae, which so closely mimic the recognition profiles of their respective hosts that nurse ants afford each parasite a social status above that of their own kin larvae. The two host ants occupy separate niches within grassland; thus, conservation management must differ in each region. Similar cryptic differentiation may be common, yet equally hard to detect, among the approximately 10 000 unstudied morpho-species of social parasite that are estimated to exist, many of which are Red Data Book listed.     

Control of Meloidogyne spp. on Russet Burbank Potato by Applying Metham Sodium through Center Pivot Irrigation Systems

Metham sodium applied in October through center pivot irrigation systems was evaluated for control of Meloidogyne hapla at 374, 468, and 701 liters/ha and for control of M. chitwoodi at 468 liters/ha on potato. Metham sodium at the high rates effectively controlled M. hapla. No females were detected in the tubers at the high rates of nematicide application, whereas a mean of 19 and 69% of the tubers were infected at the low rate and in the nontreated controls, respectively. In the M. chitwoodi trial only 1.5% of the tubers in the treated plots were infected compared with 82% in the nontreated plots. Metham sodium effectively controlled M. chitwoodi to soil depths of 30, 61, and 91 cm.     

紫花苜蓿对铜胁迫生理响应的傅里叶变换红外光谱法研究

为阐明紫花苜蓿(Medicago sativa L.)对铜胁迫的耐性机理,采用准确度好、分辨率高和简便快捷的傅里叶变换红外光谱法(FTIR)研究在不同铜浓度(0、1、5、20、100 mol/L)处理时紫花苜蓿根、茎、叶化学组分的变化。结果表明:随着铜处理浓度的增加,紫花苜蓿根、茎、叶生物量变化不大。其根组织在2924 cm~(-1)处峰高处呈现出先下降后上升的趋势,反映了在低铜(5 mol/L)处理条件下紫花苜蓿分泌的有机酸不断螯合Cu,造成羧酸0-H的减少,但随着Cu含量的升高,其羧酸螯合力变弱,有机酸含量渐渐升高;根组织在1381 cm~(-1)处峰高先下降后上升,反映了含油脂化合物含量先下降后升高。可能与植物在细胞壁结构上增强抗逆性有一定关系,即低Cu处理下细胞壁可能通过提高阳离子交换能力(CEC),增强了耐Cu性;茎组织在2924,1643,1381,1064 cm~(-1)等处峰高无明显变化;叶组织所有峰值在低浓度(5 mol/L)Cu处理下变化不明显,高浓度(5 moL/L)Cu处理下所有峰值先升后降,随着这可能与可溶性糖及可溶性蛋白质等物质含量都呈现先升后降的趋势有关。这表明紫花苜蓿通过根部有机酸含量的变化和提高细胞壁阳离子交换能力,将吸收的Cu大部分积累在根部,阻止Cu向地上部分运输,有效地保护了植物地上部分组织。     

浙江双栉蝠蛾发生与土壤关系的层次递进判别分析

为了揭示浙江双栉蝠蛾发生与土壤化学指标、土壤深度的关系,在福建省邵武市拿口镇三丰村选取春笋被浙江栉蝠蛾重度危害和轻度危害各2个样地进行调查,土壤由表及里依次分成3个层次,对每个层次测定pH值、全N含量等7个指标,采用判别分析法分别对每一层及不同层次的组合进行分析。结果表明: (1)各层独立分析,第1层单个指标中具有显著性的是有机质(X₇),判别最有效的组合是全N含量(X₂)和速效K(X₆);第2层中单个指标都不具有显著性,判别最有效的组合仍为全N含量 (X₂)和速效K(X₆);第3层单个指标中具有显著性的是有机质(X₇),判别最有效的组合是速效K(X₆)和有机质(X₇)。 (2)依据第1层判别函数能够完全正确判别分组第2层和第3层,第2层判别函数能够完全正确判别分组第3层,但第2层判别函数不能够完全正确判别分组第1层,第3层判别函数不能够完全正确判别分组第1层和第2层,判别函数具有随土壤层递进而正确判别的递进性,而不具有逆土壤层进行正确判别的逆向性。 (3)对第1层与第2层的组合、第2层与第3层的组合的判别分析,发现单个指标的显著性有所变化,但判别组合的指标没有变化,再次说明了土壤理化性状是由表及里的影响特性。 (4)与方差分析和多重比较的结果相比较,判别分析不仅能反映单个指标在分组中的显著性,而且反映出指标组合的重要性,表明单个指标的显著性不能构成对分组区别的决定性。在层次递进分析过程中,可以清晰地表明各指标在各层以及层次组合中的作用,反映出了层与层间的关系。 由此可以得出:土壤的理化性状是由表及里地影响,与浙江双栉蝠蛾发生危害程度关系密切的是全N含量 (X₂)和速效K(X₆),即全N含量 (X₂)的增加和速效K(X₆)的减少会使危害程度加重,其次为全P含量(X₃),全P含量的增加可使危害程度加重。判别分析法较方差分析和多重比较更全面深刻地反映了浙江双栉蝠蛾发生与土壤的关系。     

The crystal structure of Trypanosoma brucei enolase: visualisation of the inhibitory metal binding site III and potential as target for selective,irreversible inhibition

The glycolytic enzymes of the trypanosomatids, that cause a variety of medically and agriculturally important diseases, are validated targets for drug design. Design of species-specific inhibitors is facilitated by the availability of structural data. Irreversible inhibitors, that bound covalently to the parasite enzyme alone, would be potentially particularly effective. Here we determine the crystal structure of enolase from Trypanosoma brucei and show that two cysteine residues, located in a water-filled cavity near the active-site, are modified by iodoacetamide leading to loss of catalytic activity. Since these residues are specific to the Trypanosomatidae lineage, this finding opens the way for the development of parasite-specific, irreversibly binding enolase inhibitors. In the present structure, the catalytic site is partially occupied by sulphate and two zinc ions. Surprisingly, one of these zinc ions illustrates the existence of a novel enolase-binding site for divalent metals. Evidence suggests that this is the first direct visualization of the elusive inhibitory metal site, whose existence has hitherto only been inferred from kinetic data.     

The chemical cue tetrabromopyrrole from a biofilm bacterium induces settlement of multiple Caribbean corals

Microbial biofilms induce larval settlement for some invertebrates, including corals; however, the chemical cues involved have rarely been identified. Here, we demonstrate the role of microbial biofilms in inducing larval settlement with the Caribbean coral Porites astreoides and report the first instance of a chemical cue isolated from a marine biofilm bacterium that induces complete settlement (attachment and metamorphosis) of Caribbean coral larvae. Larvae settled in response to natural biofilms, and the response was eliminated when biofilms were treated with antibiotics. A similar settlement response was elicited by monospecific biofilms of a single bacterial strain, Pseudoalteromonas sp. PS5, isolated from the surface biofilm of a crustose coralline alga. The activity of Pseudoalteromonas sp. PS5 was attributed to the production of a single compound, tetrabromopyrrole (TBP), which has been shown previously to induce metamorphosis without attachment in Pacific acroporid corals. In addition to inducing settlement of brooded larvae (P. astreoides), TBP also induced larval settlement for two broadcast-spawning species, Orbicella (formerly Montastraea) franksi and Acropora palmata, indicating that this compound may have widespread importance among Caribbean coral species.     

洱海蓝藻水华暴发期浮游植物群落变化及影响因素

对洱海水质和浮游植物进行了调查, 分析了洱海藻类水华暴发季节水质营养水平及浮游植物多样性, 并探讨了洱海浮游植物种群演替的环境机制. 研究结果表明, 洱海蓝藻水华在6-10月份大量暴发, 蓝藻数量高达107 cells/L, 水华种类为微囊藻(Microcystis)属的一些种, 微囊藻在6-10月份占绝对优势, 最高可达90%以上. 分析5-11月洱海营养水平, 其中7月营养水平最高, 浮游植物生物量10月份最大(以叶绿素a表示). 使用SPSS里的pearson分析了浮游植物和各理化因子的关系, 结果表明相对于其他浮游植物种类, 总磷(TP)对微囊藻的影响比较大.       

Nematicidal Effects of Oxamyl Applied to Leaves of Banana Seedlings

Foliar applications of oxamyl prevented nematodes from invading roots of diploid bananas. One spray with 1,250 μg/ml was more effective than 1, 2, or 3 sprays with 625 μg/ml applied at 5-day intervals. After 3 sprays with 1,250 μg/ml, invasion may be prevented for up to 4 weeks and possibly longer. Washing roots after oxamyl treatments prevented nematicidal control. When applied to nematode-infected plants, three sprays of oxamyl decreased nematode populations in the roots.     

Effect of Aldicarb,Ethoprop, and Carbofuran on Control of Coffee Root-knot Nematode,Meloidogyne exigua

Egg hatch of Meloidogyne exigua was significantly inhibited in 14 days pretreatment with aldicarb, ethoprop, or carbofnran at concentrations higher than 0.1 μg/ml; these eggs were found to delay hatch in 19 days posttreatment in ethoprop. Aldicarb and carbofuran solutions at concentrations greater than 0.1 μg/ml significantly decreased the motility and the life span of the second-stage juveniles; aldicarb was more toxic than carbofuran to the nematode. In a field test, aldicarb (Temik 10G), ethoprop (Mocap 10G), and carbofuran (Furadan 5G and Furadan Liquid 350F) significantly decreased M. exigua populations.     

Effects of One and Two Applications of Nematicides on Nematode Populations and Soybean Yields

Yields of ''McNair 800'' soybeans, Glycine max (L.) Merr., were significantly increased with ethylene dibromide + chloropicrin, DBCP, phenamiphos, and aldicarb applied at-planting and with phenamiphos, aldicarb, and DBCP applied postplant to soil infested with Meloidogyne incognita (Kofoid and White) Chitwood. Yields of ''GaSoy 17'' were significantly increased with ethylene dibromide + chloropicrin, DBCP, phenamiphos, and aldicarb applied, preplant and with DBCP, carbofuran, phenamiphos, aldicarb, and DBCP applied postplant to soil infested with Hoplolaimus columbus Sher. In several instances, preplant or at-planting treatments plus postplant treatments with the same or different chemicals were more effective than either treatment alone. Generally, the fumigants were more effective than the nonfumigants when they were applied at-planting to M. incognita-infested soil and preplant to H. columbus-infested soil. Phenamiphos, aldicarb, and DBCP were about equally effective when they were applied postplant in M. incognita-infested soil, but DBCP was more effective than carbofuran. Carbofuran, phenamiphos, aldicarb, and DBCP were about equally effective when applied postplant to H. columbus-infested soil.     

Applying Nematicides through an Overhead Sprinkler Irrigation System for Control of Nematodes

Phenamiphos, ethoprop, and carbofuran each at 6.7 kg a.i./ha were applied to squash, southern pea, and corn via injection into a sprinkler irrigation system. This method was then compared with a conventional application of phenamiphos and ethoprop granules spread on the soil surface and incorporated into the top 15 cm for control of Macroposthonia ornata and Meloidogyne incognita. Nematode populations in the soil and root-gall indices were lower, and yields greater, in treated than in untreated plots, but there were no significant differences between the methods of application in most comparisons.