Brown rot decay of copper-chromated-phosphorus impregnated fence poles: Characterization by molecular analyses and microscopy

At one location in central Sweden, agricultural pine (Pinus sylvestris L.) fence poles treated with a commercial copper–chromium–phosphorus preservative (CCP) formulation according to use class 4 at retention of 30 kg m⁻³ were prematurely degraded by fungi after only two years in-service. Light- and electron microscopy analyses showed decay to result from primarily brown rot attack. Culture studies produced on different agar and copper-containing media using small wood slivers removed from infected poles allowed establishment of a number of pure cultures of Phycomycetes, Ascomycetes, Fungi Imperfecti and Basidiomycete fungi. Using morphological characters, PCR and sequencing of isolated strains, Antrodia vaillantii was determined as the most abundant basidiomycete present and as the major causal agent of decay. Compatibility tests and comparison of the ITS nrDNA sequences of our putative A. vaillantii isolate with other A. vaillantii strains and with Antrodia radiculosa showed differences suggesting a hybrid strain. A combination of site characteristics (e.g. hot spots of A. vaillantii), the use of juvenile poles, copper tolerance and overall ineffectivity of CCP against A. vaillantii is suggested as reasons for premature decay.     

Arbuscular mycorrhizal (AM) technology for the conservation of <Emphasis Type="Italic">Curculigo orchioides</Emphasis> Gaertn.: an endangered medicinal herb

Curculigo orchioides Gaertn. (family Hypoxidaceae) is an endangered anticarcinogenic and aphrodisiac herb, native of India. This study reports the effect of three arbuscular mycorrhizal (AM) fungal inocula on post-transplanting performance of ‘in vitro’ raised C. orchioides plantlets. The three AM fungal inocula consisted of two monospecific cultures of Glomus geosporum and G. microcarpum and one crude consortium of AM fungal spores isolated from rhizosphere soil of C. orchioides growing in natural habitat. Complete plantlets of C. orchioides were raised by direct organogenesis of leaf explants on half strength Murashige and Skoog’s medium devoid of any growth hormone. C. orchioides plantlets responded significantly different to all three mycorrhizal treatments. Mycorrhization enhanced the survival rate of C. orchioides plantlets to 100%. The inoculated plantlets fared significantly better than the uninoculated ones in terms of biomass production and number of leaves and roots per plant. Mycorrhizal plantlets exhibited higher concentrations of photosynthetic pigments as well as minerals P, Mg, Cu, Zn, Mn and Fe in both shoots and roots. Among the three inocula tested, plantlets inoculated with the mixed consortium of AM fungi consistently performed better in terms of the parameters evaluated. The study suggests use of mixed consortium of AM fungi over monospecific cultures for the sustainable cultivation and conservation of endangered medicinal plant: Curculigo orchioides.     

Topochemical investigation of early stages of lignin modification within individual cell wall layers of Scots pine (Pinus sylvestris L.) sapwood infected by the brown-rot fungus Antrodia vaillantii (DC.: Fr.) Ryv.

The initiation and progress of wood degradation of Pinus sylvestris sapwood exposed to the brown-rot fungus Antrodia vaillantii was studied on a cellular level by scanning UV microspectrophotometry (UMSP 80, Zeiss, MSP 800 Spectralytics). This improved analytical technique enables direct imaging of lignin modification within individual cell wall layers. The topochemical analyses were supplemented by light and transmission electron microscopy (TEM) studies in order to characterize morphological changes during the first days of degradation. Small wood blocks (1.5 × 1.5 × 5 mm) of Scots pine (P. sylvestris) were exposed to fungal decay by A. vaillantii for 3, 7, 11, 16, and 22 days. No significant weight loss was determined in the initial decay periods within three up to 7 days. After three days of decay the topochemical investigation revealed that the lignin modification starts at the outermost part of the secondary wall layer, especially in the region of the latewood tracheids. During advanced degradation after exposure of 22 days, lignin modification occurs non-homogeneously throughout the tissue. Even among the significantly damaged cells, some apparently unmodified cells still exist. Knowledge about lignin modification at initial stages of wood degradation is of fundamental importance to provide more information on the progress of brown-rot decay.     

Production of gibberellins and indole-3-acetic acid by Rhizobium phaseoli in relation to nodulation of Phaseolus vulgaris roots

Similar ranges of gibberellins (GAs) were detected by high-performance liquid chromatography (HPLC)-immunoassay procedures in ten cultures of wild-type and mutant strains of Rhizobium phaseoli. The major GAs excreted into the culture medium were GA₁ and GA₄. These identifications were confirmed by combined gas chromatographymass spectrometry. The HPLC-immunoassays also detected smaller amounts of GA₉- as well as GA₂₀-like compounds, the latter being present in some but not all cultures. In addition to GAs, all strains excreted indole-3-acetic acid (IAA) but there was no obvious relationship between the amounts of GA and IAA that accumulated. The Rhizobium strains studied included nod ^– and fix ^– mutants, making it unlikely that the IAA- and GA-biosynthesis genes are closely linked to the genes for nodulation and nitrogen fixation.The HPLC-immunoassay analyses showed also that nodules and non-nodulated roots of Phaseolus vulgaris L. contained similar spectra of GAs to R. phaseoli culture media. The GA pools in roots and nodules were of similar size, indicating that Rhizobium does not make a major contribution to the GA content of the infected tissue.Abbreviations EIA enzyme immunoassay - GA_n gibberellin A_n - GC-MS gas chromatography-mass spectrometry - HPLC high-performance liquid chromatography - IAA indole-3-acetic acid - Me methyl ester - RIA radioimmunoassay - TLC thin-layer chromatography     

Ethanol and acetate production by <Emphasis Type="Italic">Clostridium ljungdahlii</Emphasis> and <Emphasis Type="Italic">Clostridium autoethanogenum</Emphasis> using resting cells

Combined gasification and fermentation technologies can potentially produce biofuels from renewable biomass. Gasification generates synthesis gas consisting primarily of CO, CO₂, H₂, N₂, with smaller amounts of CH₄, NO_x, O₂, C₂ compounds, ash and tars. Several anaerobic bacteria species can ferment bottled mixtures of pure synthesis gas constituents. However, there are challenges to maintaining culture viability of synthesis gas exposed cells. This study was designed to enhance culture stability and improve ethanol-to-acetate ratios using resting (non-growing) cells in synthesis gas fermentation. Resting cell states were induced in autotrophic Clostridium ljungdahlii cultures with minimal ethanol and acetate production due to low metabolic activity compared to growing cell production levels of 5.2 and 40.1 mM of ethanol and acetate. Clostridium autoethanogenum cultures were not induced into true resting states but did show improvement in total ethanol production (from 5.1 mM in growing cultures to 9.4 in one nitrogen-limited medium) as well as increased shifts in ethanol-to-acetate production ratios.     

The effect of growth factors on anoxic chemostat cultures of two Saccharomyces cerevisiae strains

In anoxic chemostat cultures of Saccharomyces cerevisiae ATCC 4126 and CBS 8066 grown in a medium containing yeast extract, a sharp increase in the steady-state residual glucose concentration occurred at relatively low dilution rates, contrary to the expected Monod kinetics. However, supplementation with vitamins and amino acids facilitated efficient glucose uptake. This enhanced requirement for growth factors under anoxic conditions and at high growth rates could explain the exceptionally high apparent k _s values for S. cerevisiae reported in the literature.     

携带Paenibacillus polymyxa WLY78固氮基因簇(nif)的重组大肠杆菌Escherichia coli78-7转录组分析

[目的]来自Paenibacillus polymyxa WLY78的固氮基因簇（nifBHDKEfNXhesAnifV）可以转化入Escherichia coli中表达并使重组大肠杆菌合成有固氮活性的固氮酶。本文拟通过对重组大肠杆菌E.coli 78-7的转录组分析以提高其固氮能力。[方法]对固氮条件（无氧无NH₄⁺）和非固氮条件（空气和100 mmol/L NH₄⁺）培养的重组大肠杆菌E.coli 78-7进行转录组分析。[结果]nif基因在两种培养条件下显著表达,说明在重组大肠杆菌中可规避原菌中氧气和NH₄⁺对nif基因的负调控。对于固氮过程必需的非nif基因,如参与钼、硫、铁元素转运的mod、cys和feoAB,这些基因在两种培养条件下表达水平有差异。而参与铁硫簇合成的suf和isc基因簇在两条件下表达水平差异巨大。此外,参与氮代谢的基因在固氮条件下显著上调。[结论]重组大肠杆菌中与固氮相关的非nif基因在该菌的固氮过程中具有较大影响,本文对在异源宿主中调高固氮酶活性研究具有重要意义。     

连续三年夜间增温和施氮对云杉外生菌根及菌根真菌多样性的影响

以西南亚高山针叶林建群种粗枝云杉(Picea asperata)为研究对象,采用红外加热模拟增温结合外施氮肥(NH₄NO₃ 25 g N m^-2 a^-1)的方法,研究连续3a夜间增温和施肥对云杉幼苗外生菌根侵染率、土壤外生菌根真菌生物量及其群落多样性的影响。结果表明:夜间增温对云杉外生菌根侵染率的影响具有季节性及根级差异。夜间增温对春季(2011年5月)云杉1级根,夏季(2011年7月)和秋季(2010年10月)云杉2级根侵染率影响显著。除2011年7月1级根外,施氮对云杉1、2级根侵染率无显著影响。夜间增温对土壤中外生菌根真菌的生物量和群落多样性无显著影响,施氮及增温与施氮联合处理使土壤中外生菌根真菌生物量显著降低,但却提高了外生菌根真菌群落的多样性。这说明云杉幼苗外生菌根侵染率对温度较敏感,土壤外生菌根真菌生物量及其群落多样性对施氮较敏感。这为进一步研究该区域亚高山针叶林地下过程对全球气候变化的响应机制提供了科学依据。     

马尾松幼苗根系和光合碳供应对土壤性质变化和温室气体排放的驱动作用

森林植被受全球气候变化、森林经营活动及病虫害等多种干扰,导致林地光合碳供应水平及根系输入量发生变化。在此背景下,土壤性质及土壤温室气体排放的响应及其机理是预测森林碳汇功能变化及森林可持续经营的重要依据。以2年生马尾松盆栽苗为对象,通过单株/盆和3株/盆栽植密度控制根系输入量、通过环割和截干控制光合碳向地下的供应能力,模拟森林植被干扰导致的根系输入量及光合碳供应变化对土壤理化性质、微生物群落结构及温室气体排放的影响。结果表明,苗木根系非结构性碳水化合物(TNC)含量和氮含量比单株/盆低;3株/盆的土壤速效氮含量比单株/盆低,土壤革兰氏阳性菌、厌氧菌、放线菌及丛枝菌根真菌丰富度均比单株/盆显著增加,3株/盆的土壤二氧化碳(CO₂)排放速率较高,但土壤氧化亚氮(N₂O)排放速率差异不显著。无论是单株/盆还是3株/盆,环割和截干处理后,根系生物量、根系长度及表面积均比对照显著下降;根系TNC含量显著下降。土壤和根系氮含量都有增加趋势;土壤微生物生物量碳(SMBC)含量降低,而土壤微生物生物量氮(SMBN)则提高。环割和截干后,土壤中各种微生物组成丰富度均有下降趋势,土壤CO₂排放速率显著下降,土壤N₂O排放速率则显著提高。根系输入量及光合碳供应对土壤细菌和真菌含量均有显著影响,土壤细菌含量与根系生物量、SMBC和SMBN显著正相关;土壤真菌含量与土壤温度显著负相关,与根系生物量、SMBC和SMBN显著正相关。相关分析表明,土壤CO₂排放通量与土壤温度、土壤湿度及根系生物量显著正相关,与土壤硝态氮显著负相关;土壤N₂O排放通量与土壤温度和土壤湿度显著正相关。以上研究表明,根系输入量与地上光合碳供应共同作用,改变土壤理化性质及微生物环境,进而影响土壤温室气体排放。     

Ligninolytic activity and levels of ammonia assimilating enzymes in Sporotrichum pulverulentum

Levels of ammonia-assimilating enzymes (glutamate dehydrogenase, glutamine synthetase, glutamate synthase) were determined in extracts of Sporotrichum pulverulentum grown under different conditions with respect to both nitrogen source and concentration. Evolution of ¹⁴CO₂ from ¹⁴C-synthetic lignin by fungal cultures grown under parallel conditions was also determined as a measure of lignin decomposition and the suppressive effect of nitrogen on ligninolysis confirmed. Under low nitrogen conditions, fungal extracts exhibited relatively high levels of NADP-dependent glutamate dehydrogenase and glutamine synthetase dehydrogenase. Conversely, in high nitrogen extracts, lower levels of NADP-dependent glutamate dehydrogenase and glutamine synthetase activity, and higher levels of NAD-dependent glutamate dehydrogenase, were recorded. Possible effects of enzyme activities on intracellular pool concentrations of glutamate/glutamine, and the implications for the regulation of lignin metabolism, are discussed.A preliminary report was presented at The Ekman Days 1981, International Symposium on Wood and Pulping Chemistry, Stockholm, Sweden, June 9–12, 1981.     

重庆酸雨区不同林型对土壤酸化和真菌群落的影响

不同林型土壤的酸化缓冲能力不同,真菌在土壤系统中扮演着重要的角色,而对土壤真菌群落结构和组成与土壤酸化的关系缺乏深入研究。以重庆铁山坪林场的马尾松纯林（Pi）和经马尾松纯林改造后的香樟纯林（Ci）、木荷纯林（Sc）、马尾松-香樟混交林（Pi_Ci）以及马尾松-木荷混交林（Pi_Sc）为研究对象,每个林型分别设置4个20 m×20 m的样地,分别采集腐殖质层（O层）和淋溶层（A层）土壤进行土壤性质及真菌群落分析,以探讨酸雨区森林土壤真菌群落与缓解土壤酸化的关系。研究表明：（1）与Pi相比,Ci土壤酸化明显缓解（高pH低NH₄ ： NO₃）,且能有效提高土壤全磷（TP）含量;而Sc虽然土壤pH值与Pi没有显著差异,但显著（P<0.05）提高了NH₄ ： NO₃,且显著降低土壤TP和全钾（TK）含量（P<0.05）;（2）不同林型土壤真菌群落多样性以Ci最为丰富,且表征土壤酸化的指标pH值、阳离子交换量（CEC）与真菌多样性显著正相关（P<0.05）,NH₄ ： NO₃与多样性显著负相关（P<0.05）;（3）林型和土层都对真菌群落结构有显著影响（P<0.001）,且林型的影响大于土层的影响;而土壤酸化程度将五个林型的土壤真菌群落区分成两个大类：Ci和Pi_Ci;Pi,Sc以及Pi_Sc。（4） Ci中有益菌（如Mortierella）更多,Pi以外生菌根真菌占优势（Russulaceae、Russula、Tomentella以及Sebacina）;Sc以及Pi_Sc则含有更多的植物病原菌（Cladophialophora,Paecilomyces,Venturiales）、嗜酸菌及产酸菌（Paecilomyces,Penicillium）。在酸雨区受损马尾松林地种植香樟促进土壤真菌多样性提高,且产酸真菌、嗜酸菌丰度降低,而有益真菌丰度增加,可有效缓解土壤酸化;而种植木荷后土壤中的病原菌、嗜酸菌和产酸菌相对丰度增加,导致土壤进一步酸化。因此,通过将受酸雨损害严重的马尾松纯林改造成香樟纯林或马尾松-香樟混交林,有助于缓解土壤的酸化,实现酸雨区森林生态系统的可持续发展。     

Effects of carbon concentration and carbon to nitrogen ratio on the growth and sporulation of several biocontrol fungi

Effects of carbon concentration and carbon to nitrogen (C:N) ratio on six biocontrol fungal strains are reported in this paper. All fungal strains had extensive growth on the media supplemented with 6–12 g l⁻¹ carbon and C:N ratios from 10:1 to 80:1, and differed in nutrient requirements for sporulation. Except for the two strains of Paecilomyces lilacinus, all selected fungi attained the highest spore yields at a C:N ratio of 160:1 when the carbon concentration was 12 g l⁻¹ for Metarhizium anisopliae SQZ-1-21, 6 g l⁻¹ for M. anisopliae RS-4-1 and Trichoderma viride TV-1, and 8 g l⁻¹ for Lecanicillium lecanii CA-1-G. The optimal conditions for P. lilacinus sporulation were 8 g l⁻¹ carbon with a C:N ratio of 10:1 for M-14 and 12 g l⁻¹ carbon with a C:N ratio of 20:1 for IPC-P, respectively. The results indicated that the influence of carbon concentration and C:N ratio on fungal growth and sporulation is strain dependent; therefore, consideration for the complexity of nutrient requirements is essential for improving yields of fungal biocontrol agents.     

Influence of long-term treatment with pravastatin on the survival, evolution of cutaneous lesion and weight of animals infected by Leishmania amazonensis

The high toxicity of current drugs for treatment of leishmaniasis is a major hindrance for controlling the disease. Pravastatin is a well-known drug with anti-inflammatory and immunomodulatory properties that may modulate host defense mechanisms against Leishmania. We evaluated the influence of prolonged pravastatin treatment on the survival of Leishmania amazonensis-infected animals (BALB/c, C57BL6 mice and Syrian hamsters), including weekly measurement of cutaneous lesions (footpad thickness) and weight. Pravastatin improved survival of Leishmania-infected BALB/c mice but not of infected C57BL6 mice or hamsters. On the 50th week of follow-up, 71% of pravastatin-treated Leishmania-infected BALB/c mice were alive against 29% of control group (p < 0.01). Low footpad thickness was found on BALB/c pravastatin treated mice from the 14th week (p < 0.05), and 20th week onward for C57BL6 treated mice. Pravastatin treatment decreased weight loss in Leishmania-infected C57BL6 mice and Syrian hamsters, but not infected BALB/c mice. Our results points to beneficial effects of pravastatin on the evolution of the disease in the murine leishmaniasis model.     

On-line estimation of O<Subscript>2</Subscript> production,CO<Subscript>2</Subscript> uptake,and growth kinetics of microalgal cultures in a gas-tight photobioreactor

Growth of the green algae Chlamydomonas reinhardtii and Chlorella sp. in batch cultures was investigated in a novel gas-tight photobioreactor, in which CO₂, H₂, and N₂ were titrated into the gas phase to control medium pH, dissolved oxygen partial pressure, and headspace pressure, respectively. The exit gas from the reactor was circulated through a loop of tubing and re-introduced into the culture. CO₂ uptake was estimated from the addition of CO₂ as acidic titrant and O₂ evolution was estimated from titration by H₂, which was used to reduce O₂ over a Pd catalyst. The photosynthetic quotient, PQ, was estimated as the ratio between O₂ evolution and CO₂ up-take rates. NH₄ ⁺, NO₂ ⁻, or NO₃ ⁻ was the final cell density limiting nutrient. Cultures of both algae were, in general, characterised by a nitrogen sufficient growth phase followed by a nitrogen depleted phase in which starch was the major product. The estimated PQ values were dependent on the level of oxidation of the nitrogen source. The PQ was 1 with NH₄ ⁺ as the nitrogen source and 1.3 when NO₃ ⁻ was the nitrogen source. In cultures grown on all nitrogen sources, the PQ value approached 1 when the nitrogen source was depleted and starch synthesis became dominant, to further increase towards 1.3 over a period of 3–4 days. This latter increase in PQ, which was indicative of production of reduced compounds like lipids, correlated with a simultaneous increase in the degree of reduction of the biomass. When using the titrations of CO₂ and H₂ into the reactor headspace to estimate the up-take of CO₂, the production of O₂, and the PQ, the rate of biomass production could be followed, the stoichiometrical composition of the produced algal biomass could be estimated, and different growth phases could be identified.     

Evaluation of Gambierdiscus survival after exposure to ballast water

The dinoflagellate Gambierdiscus was exposed to ballast water from a trans-oceanic vessel, and maintained at a variety of temperatures in the dark to determine if viability would be maintained. Logarithmically growing Gambierdiscus inocula were admixed (1:6, vol:vol) with ballast water, maintained in the dark at 22.6 °C, 24.6 °C, 26.8 °C and 29.0 °C and assessed for numerical abundance over six days. Calculated growth rates from the biomass time series showed no indication that ballast water negatively impacted Gambierdiscus viability; accompanying microscopic inspections supported this conclusion. Filtration of large volumes of collected ballast water failed to show the presence of any Gambierdiscus cells contained therein. Recovery and microscopic examination of the experimental inocula after 10 weeks in the dark, failed to show cyst development at any temperature regime. This examination of ballast water showed no evidence of cytotoxicity to Gambierdiscus spp.     

Effects of gaseous NO2 on cells of Nitrosomonas eutropha previously incapable of using ammonia as an energy source

Cells of Nitrosomonas eutropha grown under anoxic conditions with hydrogen as electron donor and nitrite as electron acceptor were initially unable to oxidize ammonia (ammonium) and hydroxylamine when transferred to oxic conditions. Recovery of ammonia and hydroxylamine oxidation activity was dependent on the presence of NO₂. Under oxic conditions, without addition of NO₂, ammonia consumption started after 8 – 9 days, and small amounts of NO and NO₂ were detectable in the gas atmosphere. Removing these nitrogen oxides by intensive aeration, ammonia oxidation activity decreased and broke off after 15 days. Addition of gaseous NO₂ (25 ppm) led to a fast recovery of ammonia oxidation (3 days). Simultaneously, the arrangement of intracytoplasmic membranes (ICM) changed from circular to flattened vesicles, the protein pattern revealed an increase in the concentration of a 27 and a 30 kDa polypeptide, and the cytochrome c content increased significantly.     

Uptake of protoplasts from the filamentous fungiAspergillus nidulans andFusarium oxysporum into protoplasts from celery (Apium graveolens L.)

Summary Protoplasts isolated from celery cell suspension cultures, were mixed with fungal protoplasts, from either the saprophytic speciesAspergillus nidulans or the pathogenic speciesFusarium oxysporum. The incubation of protoplast mixtures with PEG caused close adhesion between plant and fungal protoplasts. Subsequent dilution of PEG resulted in the uptake of protoplasts from either fungal species into the plant protoplast cytoplasm. A range of PEG concentrations, incubation times and dilution rates were tested to maximise adhesion and uptake frequencies. Identification of uptake was achieved either by fluorescent staining of nuclei or by electron-microscopy. A maximum of 10% celery protoplasts had taken upA. nidulans protoplasts after PEG treatment. Fungal protoplasts were taken up into celery protoplast cytoplasm by endocytosis, and were maintained within vesicles; two bounding membranes were observed by electron microscopy. Plant protoplast viability was determined during prolonged incubation following fungal protoplast uptake. The presence ofA. nidulans protoplasts tended to maintain celery protoplast viability and although some morphological disintegration occurred intact celery protoplasts remained for at least 92 h after uptake. The uptake ofF. oxysporum protoplasts markedly depressed celery protoplast viability after 24 h incubation and greater celery protoplast disintegration occurred.Abbreviations PEG Polyethylene glycol - DAPI 4,6-diaminido-2-phenylindole - 2,4-D 2,4-dichlorophenoxyacetic acid     

Chitosan-mediated changes in cell wall composition, morphology and ultrastructure in two wood-inhabiting fungi

The effect of chitosan on cell wall deposition was investigated in the two wood-inhabiting fungal species Trichoderma harzianum (CBS 597.91) and Sphaeropsis sapinea (NZFS 2725). The study used three independent analytical techniques to quantify chitin in the fungal mycelium. A colorimetric method for the detection of d-glucosamine was compared with two gas chromatography–mass spectroscopy (GC-MS) methods employing alditol acetates analysis and pyrolysis. The latter used a stable-isotope-labelled internal standard, d₃-N-acetyl glucosamine. At least in the case of S. sapinea, the study provided evidence of an increase in the chitin content in the mycelium due to chitosan treatment, indicating that chitosan treatment affected cell wall deposition. Electron microscopy techniques showed alteration in surface morphology and cell wall texture due to chitosan treatment. The implications of these results are discussed with a view to analysing possible mechanisms for growth inhibitory effects of chitosan on fungal hyphae.     

Impact of moisture and UV degradation on Beauveria bassiana (Balsamo) Vuillemin conidial viability in turfgrass

Beauveria bassiana conidial viability in turfgrass was evaluated using a two-component nucleic acid stain and fluorescence microscopy. Turfgrass samples along with the top 5 cm of soil were used for conidial extraction and viability evaluation on 1, 2, 3, 7, 14 and 21 days after treatment. There were no differences in conidial viability between two Orthoptera strains, 3622 and 5977, and both strains were able to persist in a sandy loam soil for up to three weeks after application. High and low irrigation levels were applied to each of the two strains and results show that higher irrigation (5.1 cm/week) maintains conidial viability better than a low irrigation level (2.5 cm/week). Mean conidial viability was approximately 8–12% greater in plots with the high irrigation regime. Rather than significantly increase soil moisture levels, it is hypothesized that the greater amount of irrigation helps to move the conidia deeper into the thatch layer and soil profile, an area that provides protection from damaging surface temperatures and UV exposure. Rainfall that occurred during the beginning of the 2005 test minimized the irrigation effect, and the irrigation treatment differences were more pronounced after 48 h. Four different UV protectants were evaluated for an impact on conidial viability of strain 3622. Two protectants, an optical brightener and magnesium silicate clay, when added to an emulsifiable oil formulation, significantly increased conidial viability on all evaluation dates. The clay particles act as a sunlight blocker while the optical brightener absorbs UV light. The combined protection from the oil and the additive increased conidial viability by approximately 10% on all evaluation dates. Results from this study provide insight into ways to increase entomopathogenic fungal viability under field conditions.     

Submerged culture conidial germination and conidiation of the bioherbicideColletotrichum truncatum are influenced by the amino acid composition of the medium

Summary Submerged culture experiments were conducted to determine the optimal nitrogen source for rapidly producing conidia of the bioherbicide,Colletotrichum truncatum. Germination ofC. truncatum conidial inocula in submerged culture occurred most rapidly (>95% in 6 h) in media provided with a complete complement of amino acids. When (NH₄)₂SO₄, urea, or individual amino acids were provided as the sole nitrogen source, conidial germination was less than 20% after 6 h incubation. Conidia production was delayed inC. truncatum cultures grown in media with urea or individual amino acids as nitrogen sources compared to cultures supplied with Casamino acids or complete synthetic amino acid nitrogen sources. The use of methionine, lysine, tryptophan, isoleucine, leucine or cysteine as a sole nitrogen source severely inhibitedC. truncatum conidia production. Media with synthetic amino acid mixtures less these inhibitory amino acids produced significantly higher conidia yields compared to media with amino acid mixtures containing these amino acids. When various amounts of each individual inhibitory amino acid were added to media which contained amino acid mixtures, cysteine and methionine were shown to be most effective in reducing conidiation. An optimal nitrogen source forC. truncatum conidiation in submerged culture should contain a complete mixture of amino acids with low levels of cysteine, methionine, leucine, isoleucine, lysine and tryptophan for rapid conidiation and optimal conidia yield.The mention of firm names or trade products does not imply that they are endorsed or recommended by the US Department of Agriculture over other firms or similar products not mentioned.