Identification of resistance to <Emphasis Type="Italic">Bemisia tabaci</Emphasis> Genn. in closely related wild relatives of cultivated tomato based on trichome type analysis and choice and no-choice assays

The sweetpotato whitefly, Bemisia tabaci Genn., is a major pest of tomato (Solanum lycopersicum) and other crops throughout the tropics and subtropics. The objectives of this study were to characterize 255 accessions of S. galapagense, S. cheesmaniae and S. pimpinellifolium for trichome types, and to evaluate selected accessions with high densities of glandular trichomes for resistance to whitefly. Twenty-two accessions classified as either sparse or abundant for type IV trichomes were selected and evaluated for numbers of adults, eggs, nymphs, and puparium of whitefly in choice bioassays, for adult mortality and egg numbers in no-choice bioassays, and for densities of type I, IV, V, and VI trichomes. The highest whitefly resistance was detected in S. galapagense accessions VI063177 and VI037239 based on choice and no-choice bioassays. In addition, we found high levels of whitefly resistance in S. cheesmaniae accession VI037240 based on the choice bioassay and in S. pimpinellifolium accession VI030462 based on the no-choice bioassay. Whitefly resistance in VI037240 and VI030462 is noteworthy because these species are closely related to cultivated tomato and introgression of whitefly resistance should be relatively straightforward. High densities of type IV trichomes and low densities of type V trichomes were associated with reduced numbers of whitefly adults, nymphs, puparium, and eggs in the choice bioassay and with high adult whitefly mortality in the no-choice bioassay. Preliminary trichome analysis followed by choice and no-choice assays facilitated rapid identification of whitefly-resistant accessions from a large pool of candidates of different species.     

Enhanced Adsorption of Metal Ions Onto Polyethyleneimine-Impregnated Palm Shell Activated Carbon: Equilibrium Studies

In this study, palm shell activated carbon was impregnated with polyethyleneimine (PEI) and the effect of impregnation on batch adsorption of Ni²⁺, Cd²⁺or Pb²⁺ as well as the equilibrium behavior of adsorption of metal ions on PEI-impregnated AC were investigated. PEI impregnation evidently increased the single metal adsorption capacities of Ni²⁺ or Cd²⁺except for Pb²⁺, where its adsorption capacities were reduced by 16.67% and 19.55% for initial solution pH of 3 and 5 respectively. This suggested that PEI-impregnated AC could be used for selective separation of Pb²⁺ ions from other metal ions. The adsorption data of all the metal ions on both virgin and PEI-impregnated AC for both initial solution pH of 3 and 5 generally fitted the Langmuir and Redlich-Peterson isotherms considerably better than the Freundlich isotherm.     

Ophiostoma tsotsi and Ophiostoma quercus associated with Platypus cylindrus F. (Coleoptera: Curculionidae) in cork oak stands in Tunisia

Ambrosia beetles, including Platypus cylindrus, commonly act as vectors of Ophiostomatales. In an investigation of fungi associated with P. cylindrus, several species of Ophiostomatales were identified, including two species of Ophiostoma s. str. These two species were characterized based on comparisons of DNA sequences of the internal transcribed spacer regions including the 5.8S gene of rDNA and β‐tubulin gene. Two distinct clades were discernable in the phylogenetic trees, supported by high bootstrap values. One clade included the species Ophiostoma tsotsi, reported herein for the first time in Tunisia, and the species Ophiostoma quercus.     

Pathogenicity of Malaysian Phytophthora palmivora on cocoa,durian, rubber and oil palm determines the threat of bud rot disease

The epidemic of bud rot disease affecting oil palm in Colombia is primarily caused by Phytophthora palmivora. The pathogen has a cosmopolitan presence that includes Southeast Asia, but to date, bud rot has not been reported in this region. This study provides an overview of the potential risk of Malaysian P. palmivora isolates cross‐infecting other host species, including cocoa, durian, rubber and Malaysian oil palm planting materials (Dura × Pisifera, D × P). On cocoa pods, the durian isolate PP7 caused dark brown necrotic lesions. Detached leaf bioassays showed that P. palmivora isolates PP3 and PP7 infected different hosts, except rubber foliage without wounding. Inoculation tests on cocoa, durian and rubber seedlings caused brown necrotic lesions when stems were wounded, with 10% mortality in cocoa and durian at 17 days post‐inoculation (dpi). However, no further infection was observed, and lesions closed within 14–28 dpi on the non‐wounded seedlings. Pathogenicity tests of oil palm seedlings inoculated with isolates PP3 and PP7 indicated that Malaysian P. palmivora isolates were not pathogenic to oil palms based on localized infection observed only through wounding. Overall, the work demonstrated that Malaysian P. palmivora isolates were able to cross‐infect multiple hosts but did not show severe infections on oil palms.     

In field control of Botrytis cinerea by synergistic action of a fungicide and organic sanitizer

A new Integrated Pest Management program based on the combination of synthetic pesticide with a GRAS(generally recognized as safe)-classified sanitizer for the control of Botrytis cinerea in field conditions was described. The aim behind this research was to determine whether the use of this mixture would enhance the efficiency of pesticides while decreasing the recommended dose. Naturally infected tomato plants, grown in the greenhouse, were treated with two commonly used fungicides SWITCH(Syngenta, Switzerland) and SIGNUM(BASF, Germany) each alone or combined with a commercially available organic sanitizer PERACLEAN?5(Evonik Industries, Germany). A total of 27 treatments were tested consisting of three concentrations of synthetic fungicide(×1, ×1/2 and ×1/4 of the recommended dose) either applied separately or combined with three concentrations of the tested sanitizer(0.5, 1 and 1.5%). The control efficacy achieved by the fungicides applied alone ranged between 0 and 66.7% while all fungicide-sanitizer mixtures resulted in up to 70% control of grey mould. The treatment that provides the maximum control of B. cinerea was the result mixture of ×1/4 of the recommended concentration of SWITCH(15 g L~(–1)) with 0.5% of PERACLEAN~?5. This combination suppressed 85% of grey mold infections while decreasing the usually used amount of this pesticide by 75%, reducing therefore the well known negative impacts of chemical pesticides on environment and consumers health.     

Effect of altering the steric hindrance of the nitrogen atom in 2,5-bis(pyridin-n-yl)-1,3,4 thiadiazole isomers on their ability to elicit tomato defense responses against Verticillium wilt and crown gall diseases

Three isomers of the ligand 2,5-bis(pyridinyl)-1,3,4-thiadiazole, with the N atom of pyridine group in position 2, 3 or 4, named respectively, L2, L3 and L4 were compared for their use as plant defense activators. They were examined for their ability to protect tomato plants from Verticillium dahliae and Agrobacterium tumefaciens in the greenhouse, to induce reactive oxygen species and to activate plant defenses, including antioxidant enzymes. The three ligand isomers exhibited in vitro only slight inhibition of radial growth of V. dahliae, while no significant inhibition was observed for phytopathogenic bacteria. In the greenhouse, the three ligand isomers statistically reduced the severity of Verticillium wilt and crown gall on tomato plants, and the isomers L3 and L4 were the most efficient to control Verticillium wilt. This superiority was reflected in their differential ability to activate H₂O₂ accumulation, antioxidant enzymes including catalase and ascorbate peroxidase and other defense-related enzymes such as guaiacol peroxidase and polyphenol oxidase. These results demonstrated that the presence of the N atom within the two pyridinyl groups in the position 3 or 4 highly enhanced the activity of plant defense and antioxidant responses as well as their ability to reduce the severity of symptoms caused by V. dahliae on tomato.     

An Optimized Covalent Immobilization of Glucamine on Electrospun Nanofibrous Poly(vinylidene fluoride) Sheets Grafted with Oxirane Groups for Higher Boron Adsorption

Nanofibrous poly(vinylidene fluoride) (PVDF) sheets were produced by electrospinning and grafted with oxirane groups using radiation induced grafting of glycidyl methacrylate (GMA) followed by treatment with N-methyl-D-glucamine (NMDG). The NMDG density in the nanofibers was tuned by optimization of the immobilisation reaction variables using response surface methodology (RSM). The various properties of NMDG-containing nanofibers were evaluated using Fourier-transform infrared (FT-IR) spectroscopy, field emission scanning electron microscopy (FESEM), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The NMDG-containing nanofibers were tested for boron selective removal from solutions. A maximum glucamine density yield of 2.2 mmol/g was obtained at 15 wt%, 87 oC, 64.7 min and 150 % for NMDG concentration, temperature, time and degree of grafting (DG), respectively. The applied procedure incorporating RSM was found to be highly effective in the optimization of covalently immobilised glucamine on the oxirane modified PVDF based-nanofibrous structure and in imparting an excellent combination of physico-chemical and boron retention properties. A complete boron removal was achieved in 100 mg/l boron solution adsorbent with a dosage of 0.6 g at pH 7 in 2 h time. This was accompanied by a promising reusability suitable for boron removal from solutions.     

Modeling Dissolved Ozone and Bromate Ion Formation in Ozone Contactors

Many drinking water utilities that use source waters with significant bromide ion levels are currently seeking disinfection regimes that will minimize the formation of brominated disinfection byproducts while providing adequate disinfection. While ozonation appears to be a promising option for achieving these goals, the uncertainty of future drinking water regulations has developed a need for predicting actual disinfection byproduct formation prior to the costly investment for upgrading existing treatment facilities. The models developed in this paper provide comparisons of ozonation application methods, providing a basis for minimizing bromate and aiding in future design considerations. Theoretical and empirical models for the determination of ozone transferred, dissolved ozone concentrations, and bromate formation have been derived and compared with pilot-scale and full-scale data; a good agreement has been observed between the actual data and the predicted data, showing the validity of these models. True-batch bromate formation more closely simulated pilot-scale and full-scale data. Bromate formation in one stage vs two stage ozone contactors and different reactor configurations have been compared. Ozone gas phase concentration appears to have an effect on bromate formation as well.     

Identification and characterization of salt- and thermo-tolerant Leucaena-nodulating Rhizobium strains

 Rhizobium-legume symbioses are important for their nitrogen input, but salinity and elevated temperature in arid and semi-arid areas limit their effectiveness, and therefore plant growth and productivity. Sixteen Rhizobium strains isolated from root nodules of Leucaena trees grown in different geographical areas of Egypt varied in their degree of tolerance to salinity and in their symbiotic effectiveness with Leucaena leucocephala under saline conditions. Three strains were tolerant to >3% NaCl. L. leucocephala grown in the greenhouse at concentrations of NaCl up to 1.0% and inoculated either with strain DS 78 or strain DS 158 displayed significantly better growth than those plants grown at the same levels of salinity and inoculated with reference strain TAL 583. Although nine of the Rhizobium strains grew at 42  °C, their mean generation times were lengthened two- to fourfold. When daylight growth temperatures were elevated from 30  °C to 42  °C, nodule number and mass, nitrogenase activities and shoot top dry weight of plants inoculated with strains DS 78, DS 157 and DS 158 significantly increased, whereas these parameters decreased in plants inoculated with strain TAL 583. Rhizobium strains that effectively nodulate Leucaena under adverse saline conditions and at high temperatures were thus isolated, identified and characterized. Received: 12 September 1997     

Mobilization of phosphorus contributes to positive rotational effects of leguminous cover crops on maize grown on soils from northern Nigeria

Previous research has demonstrated a positive rotational effect of tropical leguminous cover crops on maize growth on a luvisol from Nigeria. This effect could not be explained by a better N supply. The objective of the present work was to further clarify whether improved P nutrition has been a contributing factor. Nine cover crops and maize were studied in nutrient solution‐culture with 1 and 20 μM P and with NO₃‐N as N source for root physiological parameters that may affect P mobilization. Zea mays, Lablab purpureus, and Centrosema pubescens responded to P deficiency by higher rates of proton excretion. Clitoria ternatea excreted OH^— with only small differences due to P nutrition. At low P supply, Chamaecrista rotundifolia, Clitoria, and Centrosema had the highest exudation rates of organic acid anions, especially citrate and malate. A major difference between plant species was found in root‐surface acid phosphatase activity. Cajanus cajan expressed the highest phosphatase activity. V_max of P uptake increased markedly under P deficiency, particularly for maize. Compared to the other plant species Cajanus, Chamaecrista, and Clitoria were characterized by a greater capability to absorb P at low external P concentrations. The nine cover crops and maize were also grown in pot experiments using two soils from northern Nigeria low in available P. The ultisol from Jos had a high P fixation capacity and was more acidic than the alfisol from Zaria. All plant species were precultured in the first season at 100 (Zaria) and 250 (Jos) mg P per pot. In the subsequent season, maize was uniformly seeded into all pots containing the remaining roots and the incorporated shoot dry mass (according to 15 mg P per pot) of the pre‐crop. No P and 250 (Zaria) or 500 (Jos) mg P per pot were freshly applied. Maize growth and P uptake were enhanced after legumes in Zaria soil. Cajanus showed the highest residual effect, and also Clitoria, Chamaecrista, and Lablab showed effects superior to the mean. In Jos soil, Clitoria, Cajanus, and Lablab enhanced maize growth above average. Also, a highly significant positive correlation between P uptake and biomass production was obtained. These results indicate that enhancement of maize growth after leguminous cover crops, at the low P supply of the soil used, mainly depends on P mobilization capacity of the cover crop.