Allelochemical ethyl 2-methyl acetoacetate (EMA) induces oxidative damage and antioxidant responses in Phaeodactylum tricornutum

Ethyl 2-methyl acetoacetate (EMA) is a novel allelochemical exhibiting inhibitory effects on the growth of marine unicellular alga Phaeodactylum tricornutum (P. tricornutum). Oxidative damage and antioxidant responses in P. tricornutum were investigated to elucidate the mechanism involved in EMA inhibition on algal growth. The increase in reactive oxygen species (ROS) levels and malondialdehyde (MDA) contents following exposure to EMA suggested that alga was suffered from oxidative stress and severely damaged. The decrease in cell activity and cellular inclusions suggested that cell growth was greatly inhibited. The activities of the antioxidant enzymes including superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), glutathione peroxide (GSH-PX) and glutathione S-transferase (GST) increased with the exposure concentration and decreased with the prolongation of exposure time. Cellular ascorbic acid (AsA) and reduced glutathione (GSH) systems were also involved in resisting oxidative stress of EMA by altering the composition of AsA and GSH pools. EMA exposure increased the contents of AsA, GSH, dehydroascorbate (DAsA) and glutathione (GSSG). However, the regeneration rate of AsA/DAsA did not change obviously between treatments and the control, while that of GSH/GSSG decreased significantly under 14 mmol/L EMA exposure on the 3rd day. These results showed that EMA-induced oxidative damage might be responsible for EMA inhibition on P. tricornutum growth and cellular antioxidant enzymes and non-enzymatic antioxidants were improved to counteract the oxidative stress.     

转Cry1Ac/1Ab基因棉花对棉铃虫的控制效果及对甜菜夜蛾和斜纹夜蛾生长发育的影响

为评估转Cry1Ac/1Ab基因棉花对棉铃虫Helicoverpa armigera的抗性及对非靶标害虫甜菜夜蛾Spodoptera exigua和斜纹夜蛾S.litura生长发育的影响,采用室内生测法测定其对棉铃虫的抗性及对甜菜夜蛾和斜纹夜蛾不同龄期幼虫存活率、营养代谢及中肠酶活性的影响。结果表明,转Cry1Ac/1Ab基因棉花对棉铃虫第2代幼虫的抗性程度最高,幼虫校正死亡率达91.33%,但对甜菜夜蛾和斜纹夜蛾的抗性程度较低,幼虫校正死亡率分别为15.33%和13.33%。甜菜夜蛾和斜纹夜蛾各龄期幼虫取食转Cry1Ac/1Ab基因棉花后,其存活率与取食常规棉花对照无显著差异;甜菜夜蛾对转Cry1Ac/1Ab基因棉花叶片的相对取食量、近似消化率分别为16.68和93.12%,均高于取食常规棉花对照的10.72和92.00%,但差异不显著,而斜纹夜蛾取食转Cry1Ac/1Ab基因棉花后的各项营养指标均低于取食常规棉花对照,差异也不显著。取食转Cry1Ac/1Ab基因棉花后,甜菜夜蛾的过氧化物酶活性为0.02 U/mg prot,显著低于取食常规棉花的0.05 U/mg prot;斜纹夜蛾的酸性磷酸酶活性为0.15 U/mg prot,高于取食常规棉花的0.10 U/mg prot,但差异不显著,其它中肠酶活性均低于对照,亦无显著差异。     

桃蚜体内次生共生菌沙雷氏菌对宿主抵御寄生蜂和高温胁迫的影响

为明确桃蚜Myzus persicae体内次生共生菌沙雷氏菌Serratia symbiotica对宿主抵抗不良环境的影响,利用叶碟法测定短翅蚜小蜂Aphelinus asychi对自然感染沙雷氏菌桃蚜、自然未感染沙雷氏菌桃蚜和人工感染沙雷氏菌桃蚜的寄生特性和取食特性,并测定烟蚜茧蜂Aphidius gifuensis对这3种处理桃蚜的寄生特性及这3种处理桃蚜经高温胁迫后的生长繁殖特性。结果显示,短翅蚜小蜂在人工感染沙雷氏菌桃蚜上的产卵率比在自然未感染沙雷氏菌桃蚜上的下降近1/2,羽化率下降1/3左右,致死率、取食率、僵蚜率均无显著差异;烟蚜茧蜂对这3种处理桃蚜的致死率、过寄生率、僵蚜率及其产卵率和羽化率等均无显著差异;这3种处理桃蚜的2龄若蚜经高温胁迫后,发育时间和寿命均显著延长,开始产蚜时间明显推迟,繁殖力和日繁殖率显著降低,繁殖历期无明显变化;高温胁迫后,人工感染沙雷氏菌桃蚜比自然未感染沙雷氏菌桃蚜开始产蚜时间提前3.9 d,繁殖力增加7.0头。表明人工感染沙雷氏菌可以提高桃蚜对短翅蚜小蜂和高温胁迫的防御作用,对烟蚜茧蜂的寄生无明显效果。     

Temperature Dependent Seed Transmission of Stagonospora nodorum in Wheat

The transmission of Stagonospora nodorum from four naturally infected winter wheat seedlots was quantified in controlled environment germination chambers at 9, 13, 17, 21, and 25 °C. Seedlings were harvested when the second leaf began to emerge. Coleoptiles and first seedling leaves were examined for the presence of lesions caused by S. nodorum. First leaves were incubated on Bannon's medium for 2 weeks, after which they were examined for pycnidia of S. nodorum. Transmission to the coleoptile occurred at all temperatures, but decreased from 100% to 72% as temperature increased from 9 to 25 °C. Transmission to the first leaf was less, dropping from 37% to 2% as temperature increased from 9 to 25 °C. At least 44% of infected first leaves were symptomless at all temperatures, with 96% of infected leaves showing no symptoms at 25 °C. Transmission to seedling leaves occurred over a broad temperature range. Under the high densities at which wheat is sown, a significant number of infected seedlings per unit area may originate from relatively low initial seed infection levels and transmission efficiencies.     

Polygalacturonase S31PG1 from <Emphasis Type="Italic">Geotrichum candidum</Emphasis> citrus race S31 expressed in <Emphasis Type="Italic">Schizosaccharomyces pombe</Emphasis> versus S31PG2 regarding soft rot on lemon fruit

Gene S31pg1, which encodes a polygalacturonase (PG), was previously isolated from citrus race S31 of Geotrichum candidum, the causal agent of citrus sour rot. We have now isolated and sequenced an additional PG gene, S31pg2, with 95% identity to S31pg1 in the mature proteins. To evaluate the contribution of the two PG genes in the development of citrus sour rot, each gene was expressed in the fission yeast Schizosaccharomyces pombe. Both genes conferred PG activity to the yeast. Crude enzyme solutions containing S31PG1 severely degraded the albedo tissue of lemon peel, but those containing S31PG2 did not. Concentrated crude S31PG1 solutions also caused soft rot on lemon fruit, indicating that not S31PG2 but S31PG1 is an important pathogenicity factor in citrus sour rot. Next, the protopectinase (PP) activity of each PG was measured. Although S31PG1 and S31PG2 are highly homologous, S31PG1 had high PP activity, whereas S31PG2 had much lower activity. PG from G. candidum noncitrus race S63 (nonpathogenic to citrus fruits) was also assayed but did not have any PP activity at all. These results suggest that the different PP activities of the PGs are a key to the pathogenicity of G. candidum to lemon fruit.     

Phosphite compounds reduce disease severity in potato seed tubers and foliage

Phosphites (Phi) are alkali metal salts of phosphorous acid, with the ability to protect plants against different pathogens. In this research, the effect of Phi applied to potato plants on severity of three important potato diseases in Argentina was assessed. Seed tubers and foliage of potato cvs Shepody and Kennebec were treated with Phi to assess effects on resistance against Phytophthora infestans, Fusarium solani and Rhizoctonia solani. Protection resulting from Phi treatment in seed tubers was high against P. infestans, intermediate against F. solani, and low against R. solani. In addition, seed tubers treated with calcium or potassium phosphites (CaPhi and KPhi, respectively) at 1% of commercial product emerged earlier than untreated ones. When Phi were foliarly applied two or four times at different doses, high levels of protection against P. infestans were achieved in both cultivars. Higher protection was observed in Kennebec when CaPhi was applied, while in Shepody this was true for KPhi. Expression of β-1,3-glucanases was induced at different times after treatment but no correlation between β-1,3-glucanases expression and foliar protection level was found. On the other hand, Phi positive protection effects did not produce negative effects in plant growth. Leaves from CaPhi-treated plants showed a darker green colour than leaves from control plants; also an increase in Rubisco protein and a delay in crop senescence was observed.     

Studies on the Interaction Between Septoria tritici and Stagonospora nodorum in Wheat

Interactions between Stagonospora nodorum and Septoria tritici were studied. Results from a detached glume experiment indicated that the interaction may be isolate-dependent, as it was shown that the interaction between the two pathogens may be beneficial or antagonistic depending on the isolate of each pathogen present. The number of spores produced by both pathogens was significantly greater when an aggressive isolate of S. tritici was mixed with a non-aggressive isolate of S. nodorum, whereas the number of spores produced by both pathogens was significantly less when two non-aggressive isolates were mixed. There was a significant reduction in disease level when S. tritici was applied prior to S. nodorum, compared to vice versa in the growth chamber. Results from growth chamber and field studies showed that S. nodorum produced significantly more spores when both pathogens were present together. It is concluded that S. tritici has a stimulatory effect on spore production by S. nodorum. However, there was a reduction of S. tritici spores observed in the dual inoculation treatments, suggesting that S. nodorum inhibits S. tritici.     

Development ofClonostachys rosea and interactions withBotrytis cinerea in rose leaves and residues

The effect of microclimate variables on development ofClonostachys rosea and biocontrol ofBotrytis cinerea was investigated on rose leaves and crop residues. C.rosea established and sporulated abundantly on inoculated leaflets incubated for 7–35 days at 10°, 20° and 30°C and then placed on paraquat—chloramphenical agar (PCA) for 15 days at 20°C. On leaflets kept at 10°C, the sporulation after incubation on PCA increased from 60% to 93% on samples taken 7 to 21 days after inoculation, but decreased to 45% on material sampled after 35 days. A similar pattern was observed on leaves incubated at either 20° or 30°C. The sporulation ofC. rosea on leaf disks on PCA was not affected when the onset of high humidity occurred 0, 4, 8, 12 or 16 h after inoculation. However, sporulation was reduced to 54–58% on leaflets kept for 20–24 h under dry conditions after inoculation and before being placed on PCA. The fungus sporulated on 68–74% of the surface of leaf disks kept for up to 24 h at high humidity after inoculation, but decreased to 40–51% if the high humidity period before transferral to PCA was prolonged to 36–48 h. The growth ofC. rosea on leaflets was reduced at low inoculum concentrations (10³ and 10⁴ conidia/ml) because of competition with indigenous microorganisms, but at higher concentrations (10⁵ and 10⁶ conidia/ml) the indigenous fungi were inhibited. Regardless of the time of application ofC. rosea in relation toB. cinerea, the pathogen’s sporulation was reduced by more than 99%. The antagonist was able to parasitize hyphae and conidiophores ofB. cinerea in the leaf residues. AsC. rosea exhibited flexibility in association with rose leaves under a wide range of microclimatic conditions, and in reducingB. cinerea sporulation on rose leaves and residues, it can be expected to suppress the pathogen effectively in rose production systems.     

Epidemiology of Toxin-Producing Fungi and Ochratoxin a Occurrence in Grape

Fungi responsible for ochratoxin A (OTA) production have been studied especially on cereals, where Penicillium verrucosum and Aspergillus ochraceus are to be considered the main producers. Until 1998, these fungi were also believed to be responsible for the production of the toxin in grape, but OTA-producing A. carbonarius and A. niger were identified in dried vine fruits in 1999. Further studies pointed out that mycoflora potentially responsible for the presence of OTA in grapes are present in the field. Aspergilli are dominant to Penicillia, and among these Aspergilli section Nigri. A. carbonarius probably plays an important role because of the high percentage of positive strains and the amount of OTA produced. Aspergilli section Nigri are present on grape bunches early in the season and their frequency increases during later growth stages. At early veraison and ripening, the incidence of colonised berries is more related to the year than to the growth stage, but not to visible symptoms, since it is normal to isolate fungi from intact berries. Differences in ochratoxin content of berries have been detected between years, when the same vineyards, managed in the same way, showed high levels (1999) or the absence (2000) of the toxin. The results suggest that meteorological differences between years and grape-growing areas are responsible for differences in OTA levels, but the data are at present insufficient to draw firm conclusions.     

玉米-大豆间作对草地贪夜蛾生长发育及繁殖的影响

为绿色防控草地贪夜蛾Spodoptera frugiperda,通过生命表研究玉米和大豆对草地贪夜蛾生长发育和繁殖能力的影响,同时室内测定草地贪夜蛾幼虫和成虫对玉米及大豆的产卵选择性和取食趋向性,并通过室内和田间小区试验研究玉米-大豆间作对草地贪夜蛾种群发生的影响。结果显示,取食大豆后草地贪夜蛾可以完成生活史,但与取食玉米相比,取食大豆会导致草地贪夜蛾发育迟缓,存活率降低,成虫期缩短,繁殖力下降和产卵天数减少;取食玉米的草地贪夜蛾种群的内禀增长率、周限增长率和净增殖率均显著高于取食大豆的草地贪夜蛾种群,取食玉米的草地贪夜蛾种群的平均世代周期低于取食大豆的种群,但两者间差异不显著。与大豆相比,草地贪夜蛾幼虫和成虫均对玉米有明显的趋性。当玉米与大豆按照2∶2比例间作时,植株上的草地贪夜蛾着卵率为65.31%,显著低于玉米单作的着卵率。当大豆包围玉米和玉米与大豆按照2∶2比例间作时,玉米的被害率分别为86.67%和85.56%,均显著低于玉米单作的被害率。表明玉米与大豆按适度比例间作可以显著降低草地贪夜蛾的发生和为害。     

帚枝霉属内生真菌激发子蛋白SbES诱导辣椒抗棒孢叶斑病作用机理

为明确帚枝霉属Sarocladium内生生防真菌HND5菌株外泌激发子蛋白SbES的诱导辣椒抗病作用机理,通过构建SbES蛋白的毕赤酵母Pichia pastoris重组蛋白表达菌株,利用纯化后的SbES重组蛋白处理辣椒植株,检测辣椒对棒孢叶斑病的抗性,以及相关抗病反应与抗病基因表达的变化。结果表明,0.1 mg/mL SbES重组蛋白可有效诱导辣椒产生对棒孢叶斑病的抗性,可激发辣椒叶片活性氧爆发、微过敏反应和胼胝质积累等抗病反应;并能有效提高辣椒叶片中与活性氧爆发、过敏性反应、胼胝质合成和植保素合成等抗病反应相关基因,以及水杨酸、茉莉酸和乙烯信号传导关键基因的表达。推测帚枝霉属内生真菌激发子蛋白SbES可通过激活多种抗病信号传导途径来激发辣椒产生对棒孢叶斑病的抗性。     

Evaluation of biocontrol preparations and plant extracts for the control of <Emphasis Type="Italic">Phytophthora infestans</Emphasis> on potato leaves

The potential of biocontrol products and plant extracts for control of late blight on potato plants, caused by Phytophthora infestans was evaluated in detached leaf assays and on potted plants. Based on an initial screening of 22 preparations and plant extracts, the 10 most active treatments were selected for further investigation. In the detached leaf assays the commercial preparations Elot-Vis, Serenade and Trichodex, and plant extracts of Rheum rhabarbarum and Solidago canadensis showed a significant effect on the level of infestation by P. infestans. However, none of the treatments was as effective as copper. In the case of Serenade, the metabolites produced by its active micro-organism, Bacillus subtilis, were demonstrated to be the effective component of the formulation, and not the micro-organism itself. In order to take curative and protective modes of action into account, the test substances were applied 24 h before, or 90 min after inoculation with P. infestans. Generally, better effects were obtained when the applications were made 24 h before inoculation. For defining the optimum time of application, potted plants were treated 72 or 24 h before, and 1 and 24 h after inoculation with P. infestans. In these tests, Trichodex showed no activity, while Elot-Vis gave best results when applied 1 day before inoculation. Serenade and the extracts of R. rhabarbarum and S. canadensis (all at 5% concentration) however, were effective when applied up to 3 days before and just after inoculation with P. infestans. The results of the experiments on potted plants indicated direct effects on the pathogen for all agents except the extract of S. canadensis, but other mode of actions, e.g. induced resistance, could not be ruled out. None of the treatments had a curative effect.     

Plant invasiveness and target plant density: high densities of native Schima wallichii seedlings reduce negative effects of invasive Ageratina adenophora

Economically feasible strategies to cope with invasive species are urgently needed. Plant density can be increased to reduce competitive effects on target plants. This study indicates that increasing native plant density can be used to reduce the effect of invasive Ageratina adenophora. Seedlings of an indigenous tree species, Schima wallichii, were grown in pots containing uninvaded or invaded soil, with or without A. adenophora leaf litter on the soil surface. Schima wallichii seedlings were also grown at four densities under four levels of A. adenophora leaf litter. Root and shoot biomass and length were measured as response parameters in both bioassays. Schima wallichii growth was inhibited by A. adenophora leaf litter and invaded soil. High litter levels reduced S. wallichii root length and dry weight at low plant densities. The inhibition disappeared at high S. wallichii plant densities. As A. adenophora did not inhibit S. wallichii growth at high plant densities, adjustments of seedling density should be studied as a possible management strategy for invasion by A. adenophora and potentially by other exotic plant species. As density‐dependent growth inhibition is the key characteristic of chemical interference, we propose that phytotoxins contribute to A. adenophora invasion particularly at low densities of native seedlings.     

Cd与Zn复合胁迫对麦长管蚜生命参数及繁殖的影响

为了明确Cd与Zn复合胁迫对麦长管蚜Sitobion avenae(Fabricius)生长发育与繁殖的影响,在室内采用不同含量Cd~(2+)与Zn~(2+)溶液交互处理土壤-小麦-麦长管蚜系统,利用特定年龄生命表研究在不同含量Cd与Zn复合胁迫下麦长管蚜生命参数及繁殖的变化规律。结果表明,Cd、Zn以及Cd与Zn交互作用均极显著影响麦长管蚜的生命参数与繁殖,其中Zn对麦长管蚜种群参数的影响最大。在40 mg/kg Cd与400 mg/kg Zn复合胁迫下,麦长管蚜种群的内禀增长率、净增值率显著高于单一Cd胁迫;但不同含量Cd与800、1 600 mg/kg高含量Zn或不同含量的Zn与120、240 mg/kg高含量Cd复合胁迫时,其内禀增长率与净增值率却逐渐下降;其平均世代周期在复合胁迫条件下显著低于单一Cd胁迫。生殖力曲线面积的变化规律与种群参数的变化规律相同,推测40 mg/kg和400 mg/kg分别为Cd与Zn复合胁迫的关键含量。研究表明,低含量Cd与Zn复合胁迫能显著促进麦长管蚜生长发育,而高含量Cd与Zn复合胁迫并不能促进麦长管蚜的生长发育。     

Insecticidal activity of crude seed extracts of<Emphasis Type="Italic">Annona</Emphasis> spp.,<Emphasis Type="Italic">Lansium domesticum</Emphasis> and<Emphasis Type="Italic">Sandoricum koetjape</Emphasis> against lepidopteran larvae

Crude ethanolic seed extracts ofAnnona muricata, A. squamosa (Annonaceae),Lansium domesticum andSandoricum koetjape (Meliaceae) collected from different locations and years in Maluku, Indonesia, were screened for inhibition of larval growth against the polyphagous lepidopteranSpodoptera litura (Noctuidae). Extracts ofA. squamosa were significantly more active (20-fold) than those ofA. muricata. A. squamosa collected from Namlea yielded the extracts with the greatest inhibitory activity. There were significant differences among locations for bothA. squamosa andA. muricata but not forL. domesticum andS. koetjape. Extracts ofA. squamosa, collected from Namlea, inhibited larval growth in a dose-dependent manner, with a dietary EC₅₀ (effective concentration to inhibit growth by 50% relative to controls) of 191.7 ppm fresh weight. Extracts ofA. squamosa collected from individual trees in Namlea also varied in growth inhibitory effect againstS. litura andTrichoplusia ni larvae. This species is a candidate for development of a botanical insecticide for local use in Indonesia. http://www.phytoparasitica.org posting Dec. 1, 2003.     

Virulence, resistance to magainin II, and expression of pectate lyase are controlled by the PhoP-PhoQ two-component regulatory system responding to pH and magnesium in Erwinia chrysanthemi 3937

Marker-exchanged mutants of phoP and phoQ of Erwinia chrysanthemi (Ech) strain 3937 became more sensitive to the cationic antimicrobial peptide (CAMP) magainin II than did the wild type at a low Mg²⁺ concentration and at either acidic or neutral pH. At high Mg²⁺ and acidic pH, only the phoQ mutant, but not the phoP mutant, became more sensitive to magainin II than did the wild type; both mutants were more sensitive at neutral pH. The hyperinduction of Pel synthesis in medium containing plant extracts and polygalacturonic acid (PGA) was confirmed in the wild type but not in the mutants at low Mg²⁺ and neutral pH. However, Pel was hyperinduced at high Mg²⁺ and neutral pH in these mutants but not in the wild type. Maceration was also greatly reduced by these mutants compared to the wild type when the inoculum was precultured and then resuspended in the medium with low Mg²⁺ at neutral pH. However, when bacteria were precultured and resuspended in the medium with high Mg²⁺ at neutral pH, severe maceration was observed in these mutants but not in the wild type. Thus, at low Mg²⁺, PhoP-PhoQ TCS seems to be stimulated for maceration and the hyperinduction of Pel synthesis. At high Mg²⁺, however, PhoP-PhoQ TCS may be repressed for these phenotypes, and PhoP may be controlled by a mechanism(s) other than PhoQ regulation.     

Identification of a new pathotype of Puccinia hordei with virulence for the resistance gene Rph7

Barley leaf rust resistance gene Rph7, derived from barley accession Cebada Capa, is the most effective R-gene for resistance to Puccinia hordei. Virulence for this gene was known in the USA, Israel and Morocco but not yet in Europe. We found an unexpected leaf rust infection in the field at Córdoba, Spain in 2004 on Rph7 carrying lines. This virulence for Rph7 was confirmed in growth chamber experiments, being the first report of Rph7 virulence in European populations of P. hordei. A collection of 680 barley accessions was screened for resistance against this new isolate. Twelve accessions showed segregation with individual plants showing resistance based on hypersensitivity (low infection type). These individual resistant plants were selected and grown in the greenhouse to obtain seeds.     

Quantification of viable <Emphasis Type="Italic">Candidatus</Emphasis> Liberibacter asiaticus in hosts using quantitative PCR with the aid of ethidium monoazide (EMA)

Citrus Huanglongbing (HLB) is a devastating disease of citrus known to be associated with a fastidious, phloem-limited Gram-negative, yet to be cultured bacterium in the genus Candidatus Liberibacter. In the present study we have developed a method to quantify viable Candidatus Liberibacter asiaticus (Las) with the aid of ethidium monoazide (EMA) which can differentiate live from dead cells. First, calibration curves were developed with the aid of quantitative real-time PCR (QPCR) by using a plasmid template consisting of a 703 bp DNA fragment of rplKAJL-rpoBC (β-operon) region. Standard equations were then developed to quantify Las genome equivalents in citrus, periwinkle, and Asian citrus psyllid, Diaphorina citri. To overcome the limitation of quantitative PCR in discriminating between live and dead bacterial cells, EMA was used to inhibit the amplification of DNA from the dead cells of Las in plant samples. By using the standard equations and EMA-QPCR methods developed in this study, we found that the proportion of viable cells in citrus and periwinkle ranged from 17–31% and 16–28%, respectively. It was determined that a minimum bacterial concentration is required for HLB symptom development by quantifying the population of Las in symptomatic and asymptomatic leaves. The EMA-QPCR methodology developed in the present study should provide an accurate assessment of viable HLB pathogen, providing a tool to investigate disease epidemiology and thus act as a crucial component for disease assessment and management. The authors P. Trivedi and U. S. Sagaram contributed equally to this work.     

A fungistatic chromene from<Emphasis Type="Italic">Ageratum conyzoides</Emphasis>

Ageratum conyzoides L. is an annual herb in the tropics and subtropics whose extracts are known to possess pharmacological and biocidal activity. We report on the bioactivity of a secondary metabolite (a chromene) isolated from the shoots ofA. conyzoides against some plant pathogenic fungi. Organic solvent extracts from the shoots were tested for antifungal activity against the plant pathogenic fungiRhizoctonia solani, Sclerotium rolfsii, Botryodiplodia theobromae, Phomopsis theae andFusarium species growingin vitro on potato dextrose agar medium. The cruden-hexane extract completely inhibited the growth ofR. solani andS. rolfsii. Then-hexane extract was chromatographed over a column of silica gel followed by activity-guided fractionation to give an antifungal principle. Structure elucidation by detailed analysis of¹H,¹³C NMR and mass spectroscopy identified the active compound as precocene II. The growth ofR. solani andS. rolfsii was completely inhibited by precocene II at a concentration of 80–100 ppm. The sclerotia ofR. solani andS. rolfsii were also completely suppressed by 150 ppm of precocene II. Sub-culture of these inhibited fungi onto precocene II-free medium restored growth of the fungus, indicating that precocene II is fungistatic. Crude or refined extracts fromA. conyzoides offer the possibility of biocontrol of plant pathogenic fungi. http://www.phytoparasitica.org posting Feb. 11, 2004.     

Entomopathogenic nematodes (Nematoda: Steinernematidae, heterorhabditidae) as control agents forParahypopta caestrum, a pest in the culture ofAsparagus officinalis

The entomopathogenic nematodes (EPNs)Steinernema feltiae (under the trade name Entonem) andHeterorhabditis bacteriophora (under the trade name Larvanem) were evaluated as potential control agents ofParahypopta caestrum, the major pest of the asparagus crop in Greece. In laboratory experiments the two nematodes provided equal insect suppression, but significant differences were found in the time it took them to kill the larvae.S. feltiae caused high levels of mortality within 24 h and the highest level at 48 h. In contrast,H. bacteriophora required 96 h to achieve the highest level of mortality. In field experiments, the nematodes provided equal insect suppression as compared with the insecticide cadusaphos and the mixture teflubenzuron +Bacillus thuringiensis var.kurstaki. No significant differences were found in the effectiveness of the insecticides used, but there were significant differences between the control and treatments. The findings showed thatS. feltiae andH. bacteriophora could be used to control the insectP. caestrum in asparagus culture. http://www.phytoparasitica.org posting Jan. 10, 2007.