Colonization of rose by Sphaerotheca pannosa (Wallr.) Lév. var. rosae Wor.

Colonization of rose by powdery mildew (Sphaerotheca pannosa) is described in terms of mycelium growth, conidiophore production and sporulation in time. The data used are gathered during different years, put together and treated by means of graphic models. Colonies could be separated into fast and slow growing colonies. Colonies initiated on leaves of increasing age showed a decreasing growth rate. Production of conidiophores and conidia started on the same day, and the relative activity of conidiophore production reached its maximum 6 days after the end of the latency period, followed 1 day later by the maximum activity of conidium production. Both conidiophore and conidium production continued for a long time at a low level. The effect of leaf age on conidiophore production found expression in differences in production rate during the first days of colony development and in final production levels. Observations on naturally infected leaves in an outdoor experiment showed a rapid decrease of sporulation on leaves of 10 days and older. Highest percentages of sporulating leaf area were observed on leaves between 7 and 10 days old.     

Expression of δ-endotoxin Cry1EC from an inducible promoter confers insect protection in peanut (Arachis hypogaea L.) plants

BACKGROUND: Spodoptera litura (F.) is a polyphagous foliage insect and a major pest on peanut (Arachis hypogaea L.). Constitutive expression of δ‐endotoxin Cry1EC gives protection against S. litura, as reported earlier. In this study, insect bites and salicylic acid induced high‐level expression of Cry1EC was achieved in peanut. In order to achieve this, the expression of pathogenesis responsive promoter PR‐1a was enhanced by placing it downstream of the CaMV35S promoter in the pCAMBIA 1300 backbone. The resultant promoter CaMV35S(r)PR‐1a expressed a high level of insecticidal δ‐endotoxin Cry1EC. The Gus expression under the control of CaMV35S(r)PR‐1a served as a convenient marker for evaluation of promoter response to different treatments. RESULTS: Transgenic events that showed a very low level of uninduced expression and no expression in seeds were selected. The Cry1EC expression in leaves increased nearly eightfold in the selected event, following induction by salicylic acid. Both the salicylic‐acid‐treated and the S. litura‐bitten leaves showed the highest expression after 2 days. Leaves from salicylic‐acid‐induced transgenic plants caused 100% mortality of S. litura at all stages of larval development. CONCLUSION: The results suggest that high expression of inducible promoters provides a good strategy for the development of safer transgenic food and feed crops. Copyright © 2010 Society of Chemical Industry     

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.     

Inheritance of resistance to Bacillus thuringiensis Cry1Ac toxin in Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) from India

BACKGROUND: The cotton bollworm, Helicoverpa armigera (Hübner), is one of the most serious insect pests of cotton. It has developed resistance to almost all groups of chemical insecticides because of their intensive use. The failure of insecticides to control H. armigera has been a strong incentive for the adoption of transgenic cotton (Bt cotton). However, the value of Bt could be diminished by widespread resistance development to Bt toxins in insect populations. Therefore, understanding the genetic basis of resistance is essential for developing and implementing strategies to delay and monitor resistance. RESULTS: A resistant strain designated as BM‐R was obtained from the cross of adults from Bathinda () and Muktsar (), Punjab, India, which showed the highest survival (60.68%) and LC₅₀ value (1.396 µg mL^?1 diet). Similarly, a laboratory‐maintained strain from Hoshiarpur, Punjab, showed maximum susceptibility to Cry1Ac toxin with the lowest LC₅₀ value (0.087 µg mL^?1), and was designated as HP‐S. The genetic purity of both strains was confirmed by RAPD profile analysis at each generation, and genetic similarity reached more than 90% after the third generation. Continuous maintenance of the resistant BM‐R strain on Cry1Ac resulted in an increase in LC₅₀ from 0.531 µg mL^?1 in F₀ to 4.28 µg mL^?1 in F₁₄ and 7.493 µg mL^?1 in F₁₉, while the LC₅₀ values for HP‐S larvae on diet without Cry1Ac increased to 0.106 and 0.104 µg mL^?1, which lay within the fiducial limits of the baseline LC₅₀ value. The mode of inheritance of resistance was elucidated through bioassay response of resistant, susceptible heterozygotes and backcross progeny to Cry1Ac incorporated in semi‐synthetic diet. CONCLUSION: Based on dominance, degree of dominance and backcross values, resistance was inferred to be polygenic, autosomal and inherited as a recessive trait. Copyright © 2011 Society of Chemical Industry     

Conjugation of δ-endotoxin from Bacillus thuringiensis with abamectin of Streptomyces avermitilis as a new type of biocide, GCSC-BtA, for control of agricultural insect pests

Conjugation of -endotoxin from Bacillus thuringiensis with abamectin, a toxin of Streptomyces avermitilis, was carried out to form a new type of biocide, GCSC-BtA based on Germany-China Scientific Cooperation research, for the control of agricultural insect pests. The strategy for biochemical linkage was designed by conjugating an amino group in B.t. protoxin with a carboxyl group in carboxylated abamectin under the treatment of conjugator EDC [1-Ethyl-3-(3-dimethylaminopropyl carbodiimide Hydrochloride)]. The formation of B.t. protoxin was processed by solubilizing B.t. crystal in 25mM dithiothreitol (DTT) at 37°C for 2h. The carboxylated abamectin was formed by carboxylating the NaH-activated abamectin with 10mg/ml butyric anhydride at 111°C in a water-circumfluent condensation device for 2h. The conjugating reaction, consisting of 5mg/ml B.t. protoxin, 10mg/ml carboxylated abamectin and 19.17mg/ml EDC, was successfully conducted at room temperature for 24h. Significant differences were found between pure abamectin, carboxylated abamectin and the conjugated BtA by means of UV-photo absorptions recorded at wavelengths 354, 438, 518, 600nm (P<0.01). LT₅₀ of the conjugated GCSC-BtA to the 3^rd instar larvae of Plutella xylostella (L.) (Lep., Plutellidae) was 35.27 g a.i./ml, about 62% and 76% of that caused by the B.t. protoxin and the caxboxylated abamectin, respectively. The conjugated GCSC-BtA caused 87.14% mortalities in larvae of P. xylostella, 93.75% in adult Myzus persicae (Sulzer) (Hom., Aphididae) and 89.33% in adult Phyllotreta vittata Fabricius (Col., Chrysomelidae) as compared to 48.33% by the B.t. crystal only in P. xylostella. The symptoms caused by conjugated GCSC-BtA in the 3^rd instar of P. xylostella were black color in the head part and white-yellow in the abdomen of dead larvae, which differed from the black color or the white-yellow all along the body caused by either the B.t. crystal or the abamectin, respectively. It was concluded that the conjugated GCSC-BtA biocide had a broader host spectrum and a faster killing speed than either the B.t. crystal or abamectin alone for the control of agricultural pests.     

Long-term selection for resistance to transgenic cotton expressing Bacillus thuringiensis toxin in Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae)

Selection experiments for resistance to transgenic Bt cotton expressing Cry1Ac toxin in Helicoverpa armigera (Hübner) were conducted using a leaf-feeding method with 42 selection episodes over 45 generations. The cotton bollworm developed resistance to transgenic Bt cotton after 12 generations (F12) of selection. The survival rate of F12 neonates feeding on leaves of seedling stage for 4 days and boll-opening stage for 5 days of R19 line were ca 34 and 72%, respectively, compared with ca 0 and 40% for a non-selected sister strain (NYCS), but lower than or similar to that of F12 feeding on leaves of non-Bt cotton, Sumian 12 (ca 87 or 76%). Resistance to B thuringiensis HD-1 Dipel in neonates (F12) was ca 6-fold. After 42 generations of selection, the strain developed a very high level of resistance to Cry1Ac protoxin, 210 g kg(-1) MVPII wettable powder and 200 g litre(-1) MVPII liquid formulation, the resistance ratios being 1680-, 1780- and ca 1200-fold, respectively, compared with a laboratory susceptible strain (HZS). When compared with the non-selected NYCS, the resistance ratios to the above toxins were ca 540-, 580- and 510-fold, respectively, but to Dipel only ca 16-fold. The results indicated that it is very important to develop and implement effective resistance-management strategies and to detect early resistance to Bt cotton in field populations.     

Radial profile of sap flow velocity in mature Xinjiang poplar（Populus alba L. var. pyramidalis） in Northwest China

Estimation of the transpiration rate for a tree is generally based on sap flow measurements within the hydro-active stem xylem. In this study, radial variation of sap flow velocity(Js) was investigated at five depths of the xylem(1, 2, 3, 5 and 8 cm under the cambium) in three mature Xinjiang poplar(Populus alba L. var. pyramidalis) trees grown at the Gansu Minqin National Studies Station for Desert Steppe Ecosystem from May to October 2011. Thermal dissipation probes of various lengths manufactured according to the Granier's design were installed into each tree for simultaneous observation of the radial patterns of Js through the xylem. The radial patterns were found to fit the four-parameter GaussAmp equation. The peak Js was about 27.02±0.95 kg/(dm2?d) at approximately 3 to 5 cm deep from the cambium of the three trees,and the lowest Js appeared at 1 cm deep in most of the time. Approximately 50% of the total sap flow in Xinjiang poplar occurred within one-third of the xylem from its outer radius, whereas 90% of the total sap flow occurred within two-fifth of the xylem. In addition, the innermost point of the xylem(at 8-cm depth), which appeared as the penultimate sap flow in most cases during the study period, was hydro-active with Js,8 of 7.55±3.83 kg/(dm2?d). The radial pattern of Js was found to be steeper in midday than in other time of the day, and steeper diurnal fluctuations were recorded in June, July and August(the mid-growing season). Maximum differences between the lowest Js(Js,1 or Js,8) and the highest Js(Js,3 or Js,5) from May through October were 12.41, 17.35, 16.30, 18.52, 12.60 and 16.04 g/(cm2?h), respectively. The time-dependent changes of Js along the radial profile(except at 1-cm depth) were strongly related to the reference evapotranspiration(ET0). Due to significant radial variability of Js, the mean daily sap flow at the whole-tree level could be over-estimated by up to 29.69% when only a single probe at depth of 2 cm was used. However, the accuracy of the estimation of sap flow in Xinjiang poplar could be significantly improved using a correction coefficient of 0.885.     

Evidence for the involvement of Aphanomyces cochlioides and Pythium spp. in ‘girth scab’ disease of sugar beet in Bavaria

Journal of Plant Diseases and Protection - The term ‘girth scab’ describes a chronic disease of sugar beet roots (Beta vulgaris ssp. vulgaris) for which the causes still remain unclear....     

Mode of action of sulfenylated carbamates: Rapid conversion of N,N′-thiodicarbamates to parent carbamate measured by neurophysiological bioassay

Four N,N′-thiodicarbamate derivatives of carbofuran induced uncoupled convulsions with similar latencies following topical application to the cuticle of tethered S_NAIDM house flies, despite considerable differences in their lipophilic properties. There was a small but statistically significant delay in the latency to response to the derivatives compared to carbofuran, but when perfused directly on the exposed thoracic ganglia to assess intrinsic activity, carbofuran acted up to 4.4 times faster than the derivative. It is suggested that the NS bond of the derivatives is cleaved soon after application to the house fly cuticle and carbofuran is released from each derivative in sufficient quantities to accumulate toxic concentrations in the central nervous system at similar rates.     

Structure of populations of wheat powdery mildew (Erysiphe graminis DC f.sp. tritici Marchal) in Central Europe in 1993–1996: I. Dynamics of virulence

In 1993–1996, the virulence of regional populations of the wheat powdery mildew pathogen (Erysiphe graminis DC f. sp. tritici Marchal) from the Czech Republic, Austria, Hungary and Slovakia against 13 resistance genes was investigated. The populations differed mainly at the regional level. Populations from the Czech Republic, mainly from the western regions, showed higher values of virulence against the Pm4b gene. Lower frequency of virulence against Pm4b was found in Austria, and the lowest value was observed in Hungary. The differences in frequencies of virulence against Pm4a and Pm4b showed a similar geographic pattern across the four countries: a continuous decline from west to east and from north to south. Virulence against Pm2 decreased in all countries considered; virulence to pm5, Pm6, Pm8 and Mli was high throughout. Genes and gene combinations that can ensure a relatively effective biological protection against this pathogen across Central Europe at present are Pm3b, Pm2+Mld and Pm1+2+9. Czech and Slovak populations were the most complex: virulence complexity reached a maximum in Slovakia in 1994. A similar evolution, though less significant, was observed in the Czech Republic. Data on complexity of isolates suggest that Central European populations of wheat powdery mildew tend to reach an intermediate level representing the optimal number of virulence genes. This process is probably a consequence of stabilizing selection.     

Characterization of the mode of action of the experimental herbicide LS 82–556: [(S)3-N-(Methylbenzyl)carbamoyl-5-propionyl-2,6-lutidine]

The herbicidal activity of the pyridine derivative LS 82–556 [(S)3-N-(methylbenzyl)carbamoyl-5-propionyl-2,6-lutidine] has been studied on green or etiolated seedlings of cucumber (Cucumis sativus L. cv Vert Long Maraîcher), wheat (Triticum aestivum L. cv Fidel), and maize (Zea mays L. cv Monclair). The symptoms were strictly light dependent, and consisted of bleaching, wilting, and desiccation of leaves and stems. In green seedlings pretreated for 24 hr in the dark with 10 μM LS 82–556, increases in ethane evolution and thiobarbituric acid-reacting material content could be detected after a 3-hr exposure to high light intensity (400 μE m⁻² sec⁻¹ photosynthetically active radiation). Similar increases were also detected in etiolated seedlings. Electron microscope observations of treated tissues exposed to light for 6 hr or more revealed structural damage at the level of cellular membranes (chloroplast envelope, tonoplast, and plasma membrane). In cotyledons or leaves grown in the light, activity of LS 82–556 required the presence of chloroplastic pigments. All the above results suggest that as for diphenyl ether herbicides, the mechanism of action of LS 82–556 involves photooxidative reactions leading to the degradation of fatty acids. A further analogy between the two types of herbicide action comes from their similar requirement for an operating photosynthetic electron flow when they are administered to green tissues.     

Lamb’s lettuce (Valerianella olitoria): new host of Fusarium oxysporum f. sp. conglutinans

Journal of Plant Diseases and Protection - A new wilt of lamb’s lettuce (Valerianella olitoria) was detected in northern Italy in 2003 and the causal agent of the disease was identified as...     

Margaritaella gracilis gen. n. et sp. n. (Eucestoda: Proteocephalidea), a parasite of Callichthys callichthys (Pisces: Siluriformes) from the Paraná River basin, Argentina

Margaritaella gracilis gen. n. et sp. n. (Proteocephalidea: Proteocephalinae) found in the intestine of Callichthys callichthys (Linnaeus) from the Paraná River basin is described. The new genus is placed in the Proteocephalinae because of the medullary position of the genital organs. It differs from all known genera included in the Proteocephalinae by the following combination of characters: 1) scolex with a conspicuous cluster of drop-shaped gland cells posterior to suckers; 2) strobila with a low number of proglottides, all much longer than wide; 3) testes arranged in one field, composed of two parallel rows of testes separated by the uterus; 4) ovary delicate, H-shaped, with branches slender and deeply folliculate at the edges, located at 25-35% from the posterior end; 5) uterus largely extended posterior to the ovary but not reaching the end of proglottis; and 6) vitelline follicles in two narrow lateral bands, largely extended posterior to the ovary. Scanning electron microscopy revealed three types of microtriches on the tegument surface: acicular and capiliform filitriches and gladiate spinitriches. The relative size of the ovary, a character recently used in the systematics of the proteocephalidean cestodes, was calculated for the new species and compared with other species of the group. M. gracilis is the first record of a proteocephalidean cestode parasitizing a callichthyid catfish.     

Measures aimed at controlling the invasion of Simulium damnosum Theobald s.l. (Diptera: Simuliidae) into the Onchocerciasis Control Programme Area. III. Searches in the Upper Niger Basin of Guinea for additional sources of flies invading south‐eastern Mali

Abstract

Very large breeding sites of the onchocerciasis vector, Simulium sirbanum were discovered along the Rivers Niger, Mafou, Kouya, Niandan and Milo in the Upper Niger Basin of Guinea. Flies reared from these breeding sites and caught biting man nearby were found to be in the same size range as those collected in the south‐eastern Mali invasion zone of the Onchocerciasis Control Programme Area. The periodicity of the Mali invasion appeared to be related to the hydrological conditions in the Upper Niger Basin during the early monsoon. During this period, rising water levels greatly increase vector breeding in the principal rapids of the Niger and its tributaries which lie upwind and to the south‐west of the invasion sites in south‐eastern Mali. The Mali invasion ceases towards the height of the rainy season when many of these rapids are flooded. It was concluded that the very large breeding sites associated with the principal rapids in the Upper Niger Basin were the main sources of the S. sirbanum invading south‐eastern Mali.     

Quantitative structure-activity studies of pyrethroids: 12. Physicochemical substituent effects of meta-phenoxybenzyl α,α-disubstituted acetates on insecticidal activity

The insecticidal activity of a series of m-phenobenzyl esters of iso-valeric and tert-butylacetic acids, the α-position of which was substituted with one of alkyl, alkoxyalkyl, alkoxy, benzyl, phenyl, phenoxy, and anilino groups, was measured by injection into American cockroaches under synergistic conditions to suppress possible oxidative and hydrolytic metabolism. Their neuroexcitatory activity on nerve preparations excised from the cockroaches was measured by an extracellular recording technique. The activities of the analogous esters of cyclopropanecarboxylic acids with a substituted vinyl side chain were also measured. The insecticidal activity was quantitatively analyzed with physicochemical parameters for the α-substituent or its counterpart of the acid moiety. Variations in the activity were related parabolically to both the hydrophobicity and the length of the substituent. The activity of compounds, the α-substituent of which is either a substituted phenyl or a phenoxy group, was about 10 times that of compounds with “physicochemically equipvalent” aliphatic substituents. α-Substitution with ring-substituted anilino groups, but not with N-methyl groups, enhanced the activity about 25 times, but the vinylcyclopropane structure raised the activity to about 60 times that of physicochemically equivalent aliphatic noncyclopropane substituents. Variations in the insecticidal activity were closely related to those in the neuroexcitatory activity when hydrophobic and steric factors were separated. The steric factor in addition to the hydrophobicity seemed to be important in the transport process.     

Pomphorhynchus omarsegundoi sp. n. (Acanthocephala:Pomphorhynchidae), parasite of the banded knifefish Gymnotus carapo (Gymnotiformes:Gymnotidae) from the Paraná River basin, Argentina

Pomphorhynchus omarsegundoi sp. n. from Gymnotus carapo Linnaeus from the Paraná River basin in Argentina is described in this paper. The new species is characterised by having a small body; a non-spirally twisted long neck forming an inconspicuous asymmetrical bulb more developed dorsally than ventrally; a proboscis almost cylindrical, with 11 to 12 longitudinal rows of 5 to 7 (usually 6) hooks each; presence of an apical organ; a mean neck/body ratio of about 1/8; and a post-equatorial male reproductive system, occupying 35-42% of total length. The new species can be easily distinguished from the other four South American pomphorhynchid species by the inconspicuous asymmetrical bulb and the lower number of hooks per row. Pomphorhynchus omarsegundoi is the second acanthocephalan recorded from G. carapo in the Paraná River basin.