Arnon Dag

Bio: Arnon Dag is an academic researcher from Agricultural Research Organization, Volcani Center. The author has contributed to research in topics: Olive trees & Honey bee. The author has an hindex of 32, co-authored 142 publications receiving 3277 citations. Previous affiliations of Arnon Dag include Ministry of Agriculture and Rural Development & Hebrew University of Jerusalem.

Standard methods for pollination research with Apis mellifera

Abstract: Summary In this chapter we present a synthesis of recommendations for conducting field experiments with honey bees in the context of agricultural pollination. We begin with an overview of methods for determining the mating system requirements of plants and the efficacy of specific pollinators. We describe methods for evaluating the pollen-vectoring capacity of bees at the level of individuals or colonies and follow with methods for determining optimum colony field stocking densities. We include sections for determining post-harvest effects of pollination, the effects of colony management (including glasshouse enclosure) on bee pollination performance, and a brief section on considerations about pesticides and their impact on pollinator performance. A final section gives guidance on determining the economic valuation of honey bee colony inputs at the scale of the farm or region.

Trichoderma biocontrol of Colletotrichum acutatum and Botrytis cinerea and survival in strawberry

Abstract: Trichoderma isolates are known for their ability to control plant pathogens. It has been shown that various isolates of Trichoderma, including T. harzianum isolate T-39 from the commercial biological control product TRICHODEX, were effective in controlling anthracnose (Colletotrichum acutatum) and grey mould (Botrytis cinerea) in strawberry, under controlled and greenhouse conditions. Three selected Trichoderma strains, namely T-39, T-161 and T-166, were evaluated in large-scale experiments using different timing application and dosage rates for reduction of strawberry anthracnose and grey mould. All possible combinations of single, double or triple mixtures of Trichoderma strains, applied at 0.4% and 0.8% concentrations, and at 7 or 10 day intervals, resulted in reduction of anthracnose severity; the higher concentration (0.8%) was superior in control whether used with single isolates or as a result of combined application of two isolates, each at 0.4%. Only a few treatments resulted in significant control of grey mould. Isolates T-39 applied at 0.4% at 2 day intervals, T-166 at 0.4%, or T-161 combined with T-39 at 0.4% were as effective as the chemical fungicide fenhexamide. The survival dynamics of populations of the Trichoderma isolates (T-39, T-105, T-161 and T-166) applied separately was determined by dilution plating and isolates in the mixtures calculated according to the polymerase chain reaction (PCR) using repeat motif primers. The biocontrol isolates were identified to the respective species T. harzianum (T-39), T. hamatum (T-105), T. atroviride (T-161) and T. longibrachiatum (T-166), according to internal transcribed spacer sequence analysis.

Evaluating water stress in irrigated olives: correlation of soil water status, tree water status, and thermal imagery

Abstract: Irrigation of olive orchards is challenged to optimize both yields and oil quality. Best management practices for olive irrigation will likely depend on the ability to maintain mild to moderate levels of water stress during at least some parts of the growing season. We examined a number of soil, plant and remote sensing parameters for evaluating water stress in bearing olive (var. Barnea) trees in Israel. The trees were irrigated with five water application treatments (30, 50, 75, 100 and 125% of potential evapotranspiration) and the measurements of soil water content and potential, mid-day stem water potential, and stomatal resistance were taken. Remote thermal images of individual trees were used to alternatively measure average canopy temperature and to calculate the tree’s crop water stress index (CWSI), testing empirical and analytical approaches. A strong non-linear response showing similar trends and behavior was evident in soil and plant water status measurements as well as in the CWSI, with decreasing rates of change at the higher irrigation application levels. No statistically significant difference was found between the analytical and the empirical CWSI, suggesting that the relative simplicity of the analytical method would make it preferable in practical applications.

Omega-3 deficiency impairs honey bee learning

Abstract: Deficiency in essential omega-3 polyunsaturated fatty acids (PUFAs), particularly the long-chain form of docosahexaenoic acid (DHA), has been linked to health problems in mammals, including many mental disorders and reduced cognitive performance. Insects have very low long-chain PUFA concentrations, and the effect of omega-3 deficiency on cognition in insects has not been studied. We show a low omega-6:3 ratio of pollen collected by honey bee colonies in heterogenous landscapes and in many hand-collected pollens that we analyzed. We identified Eucalyptus as an important bee-forage plant particularly poor in omega-3 and high in the omega-6:3 ratio. We tested the effect of dietary omega-3 deficiency on olfactory and tactile associative learning of the economically highly valued honey bee. Bees fed either of two omega-3-poor diets, or Eucalyptus pollen, showed greatly reduced learning abilities in conditioned proboscis-extension assays compared with those fed omega-3-rich diets, or omega-3-rich pollen mixture. The effect on performance was not due to reduced sucrose sensitivity. Omega-3 deficiency also led to smaller hypopharyngeal glands. Bee brains contained high omega-3 concentrations, which were only slightly affected by diet, suggesting additional peripheral effects on learning. The shift from a low to high omega-6:3 ratio in the Western human diet is deemed a primary cause of many diseases and reduced mental health. A similar shift seems to be occurring in bee forage, possibly an important factor in colony declines. Our study shows the detrimental effect on cognitive performance of omega-3 deficiency in a nonmammal.

Modern Applied Statistics With S

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Botrytis cinerea: the cause of grey mould disease

Abstract: Introduction: Botrytis cinerea (teleomorph: Botryotinia fuckeliana) is an airborne plant pathogen with a necrotrophic lifestyle attacking over 200 crop hosts worldwide. Although there are fungicides for its control, many classes of fungicides have failed due to its genetic plasticity. It has become an important model for molecular study of necrotrophic fungi. Taxonomy: Kingdom: Fungi, phylum: Ascomycota, subphylum: Pezizomycotina, class: Leotiomycetes, order: Helotiales, family: Sclerotiniaceae, genus: Botryotinia. Host range and symptoms: Over 200 mainly dicotyledonous plant species, including important protein, oil, fibre and horticultural crops, are affected in temperate and subtropical regions. It can cause soft rotting of all aerial plant parts, and rotting of vegetables, fruits and flowers post-harvest to produce prolific grey conidiophores and (macro)conidia typical of the disease. Pathogenicity: B. cinerea produces a range of cell-wall-degrading enzymes, toxins and other low-molecular-weight compounds such as oxalic acid. New evidence suggests that the pathogen triggers the host to induce programmed cell death as an attack strategy. Resistance: There are few examples of robust genetic host resistance, but recent work has identified quantitative trait loci in tomato that offer new approaches for stable polygenic resistance in future.

Cation exchange capacity.

Abstract: Positive ions that are available in soils absorb on grain surfaces. The total sum of cations that can be absorbed bij a soil/sediment at a certain PH is defined by the cation-exchange capacity (CEC, in meq g-1: mol equivalents per gram). The uptake of cations is an important parameter in agriculture and the larger the CEC, the more cations can be absorbed to the soil. The CEC depends highly on the pH of soil and sediments, where the CEC decreases with decreasing PH (increasing acidity). The exchange of ions on sediments occurs commonly fast on geological time scales, but the kinetics of adsorption in natural environments is still poorly understood. The strength of the bonding between the cations and the sediments varies from weak Van der Waals bondings (physical adsorption) to strong chemical bonds. The CEC is widely used for agricultural assessment because it is a measure of general soil fertility as well as an indicator of structural stability because CED is capabel of enhancing development of shrinkage cracks. The list below shows the CEC for different types of minerals. The data indicate that the CEC can vary over 2 orders of magnitude for various types of , minerals and can vary one order of magnitude within one soil type. Cation exchange capacity for different types of sediment (Eisma, 1992; Locher and de Bakker, 1990):

Phytoremediation : 植物による環境/土壌浄化

Abstract: In addition to the often-cited advantages of using Arabidopsis thaliana as a model system in plant biological research (1), Arabidopsis has many additional characteristics that make it an attractive experimental organism for studying lea d (Pb) accumulation and tolerance in plants. These include its fortuitous familial relationship to many known metal hyperaccumulators (Brassicaceae), as well as similar Pbaccumulation patterns to most other plants. Using nutrient-agar plates, hydroponic culture, and Pb-contaminated soils as growth media, we found significant variation in Arabidopsis thaliana ecotypes in accumulation and tolerance of Pb. In addition, we have found that Pb accumulation is not obligatorily linked with Pb tolerance, suggesti ng that different genetic factors control these two processes. We also screened ethyl methanesulfonate-mutagenized M2 populations and identified several Pb-accumulating mutants. Current characterization of these mutants indicates that their phenotypes are likely due to alteration of general metal ion uptake or translocation processes since these mutants also accumulate many other metals in shoots. We expect that further characterization of the ecotypes and mutants will shed light on the basic genetic and physiological underpinnings of plant-based Pb remediation. 7. Aromatic nitroreduction of acifluorfen in soils, rhizospheres, and pure cultures of rhizobacteria. Zablotowicz, R. M., Locke, M. A., and Hoagland, R. E. Phytoremediation of soil and water contaminants. Washington, DC : American Chemical Society, 1997. p. 38-53. NAL Call #: QD1.A45-no.664 Abstract: Reduction of nitroaromatic compounds to their corresponding amino derivatives is one of several pathways in the degradation of nitroxenobiotics. Our studies with the nitrodiphenyl ether herbicide acifluorfen showed rapid metabolism to am inoacifluorfen followed by incorporation into unextractable soil components in both soil and rhizosphere suspensions. Aminoacifluorfen was formed more rapidly in rhizospheres compared to soil, which can be attributed to higher microbial populations, espec ially of Gram-negative bacteria. We identified several strains of Pseudomonas fluorescens that possess nitroreductase activity capable of converting acifluorfen to aminoacifluorfen. Factors affecting acifluorfen nitroreductase activity in pure cultures an d cell-free extracts, and other catabolic transformations of acifluorfen, ether bond cleavage, are discussed. Plant rhizospheres should be conducive for aromatic nitroreduction. Nitroreduction by rhizobacteria is an important catabolic pathway for the ini tial degradation of various nitroherbicides and other nitroaromatic compounds in soils under Reduction of nitroaromatic compounds to their corresponding amino derivatives is one of several pathways in the degradation of nitroxenobiotics. Our studies with the nitrodiphenyl ether herbicide acifluorfen showed rapid metabolism to am inoacifluorfen followed by incorporation into unextractable soil components in both soil and rhizosphere suspensions. Aminoacifluorfen was formed more rapidly in rhizospheres compared to soil, which can be attributed to higher microbial populations, espec ially of Gram-negative bacteria. We identified several strains of Pseudomonas fluorescens that possess nitroreductase activity capable of converting acifluorfen to aminoacifluorfen. Factors affecting acifluorfen nitroreductase activity in pure cultures an d cell-free extracts, and other catabolic transformations of acifluorfen, ether bond cleavage, are discussed. Plant rhizospheres should be conducive for aromatic nitroreduction. Nitroreduction by rhizobacteria is an important catabolic pathway for the ini tial degradation of various nitroherbicides and other nitroaromatic compounds in soils under phytoremediation management. 8. Ascorbate: a biomarker of herbicide stress in wetland plants. Lytle, T. F. and Lytle, J. S. Phytoremediation of soil and water contaminants. Washington, DC : American Chemical Society, 1997. p. 106-113. NAL Call #: QD1.A45-no.664 Abstract: In laboratory exposures of wetland plants to low herbicide levels (<0.1 micrograms/mL), some plants showed increased total ascorbic acid suggesting a stimulatory effect on ascorbic acid synthesis occurred; at higher herbicide conce ntrations (greater than or equal to 0.1 micrograms/mL) a notable decline in total ascorbic acid and increase in the oxidized form, dehydroascorbic acid occurred. Vigna luteola and Sesbania vesicaria were exposed for 7 and 21 days respectively to atrazine (0.05 to 1 microgram/mL); Spartina alterniflora 28 days at 0.1 micrograms/mL trifluralin; Hibiscus moscheutos 14 days at 0.1 and 1 microgram/mL metolachlor in fresh and brackish water. The greatest increase following low dosage occurred with S. alterniflo ra, increasing from <600 micrograms/g wet wt. total ascorbic acid to >1000 micrograms/g. Ascorbic acid may be a promising biomarker of estuarine plants exposed to herbicide runoff; stimulation of ascorbic acid synthesis may enable some wetland plant s used in phytoremediation to cope with low levels of these compounds. In laboratory exposures of wetland plants to low herbicide levels (<0.1 micrograms/mL), some plants showed increased total ascorbic acid suggesting a stimulatory effect on ascorbic acid synthesis occurred; at higher herbicide conce ntrations (greater than or equal to 0.1 micrograms/mL) a notable decline in total ascorbic acid and increase in the oxidized form, dehydroascorbic acid occurred. Vigna luteola and Sesbania vesicaria were exposed for 7 and 21 days respectively to atrazine (0.05 to 1 microgram/mL); Spartina alterniflora 28 days at 0.1 micrograms/mL trifluralin; Hibiscus moscheutos 14 days at 0.1 and 1 microgram/mL metolachlor in fresh and brackish water. The greatest increase following low dosage occurred with S. alterniflo ra, increasing from <600 micrograms/g wet wt. total ascorbic acid to >1000 micrograms/g. Ascorbic acid may be a promising biomarker of estuarine plants exposed to herbicide runoff; stimulation of ascorbic acid synthesis may enable some wetland plant s used in phytoremediation to cope with low levels of these compounds. 9. Atmospheric nitrogenous compounds and ozone--is NO(x) fixation by plants a possible solution. Wellburn, A. R. New phytol. 139: 1 pp. 5-9. (May 1998). NAL Call #: 450-N42 Descriptors: ozoneair-pollution nitrogen-dioxide nitric-oxide air-quality tolerancebioremediationacclimatizationnutrient-sources nutrient-uptake plantscultivarsgenetic-variation literature-reviews 10. Atrazine degradation in pesticide-contaminated soils: phytoremediation potential. Kruger, E. L., Anhalt, J. C., Sorenson, D., Nelson, B., Chouhy, A. L., Anderson, T. A., and Coats, J. R. Phytoremediation of soil and water contaminants. Washington, DC : American Chemical Society, 1997. p. 54-64. NAL Call #: QD1.A45-no. 664 Abstract: Studies were conducted in the laboratory to determine the fate of atrazine in pesticide-contaminated soils from agrochemical dealer sites. No significant differences in atrazine concentrations occurred in soils treated with atrazine i ndividually or combinations with metolachlor and trifluralin. In a screening study carried out in soils from four agrochemical dealer sites, rapid mineralization of atrazine occurred in three out of eight soils tested, with the greatest amount occurring i n Bravo rhizosphere soil (35% of the applied atrazine after 9 weeks). Suppression of atrazine mineralization in the Bravo rhizosphere soil did not occur with the addition of high concentrations of herbicide mixtures, but instead was increased. Plants had a positive impact on dissipation of aged Studies were conducted in the laboratory to determine the fate of atrazine in pesticide-contaminated soils from agrochemical dealer sites. No significant differences in atrazine concentrations occurred in soils treated with atrazine i ndividually or combinations with metolachlor and trifluralin. In a screening study carried out in soils from four agrochemical dealer sites, rapid mineralization of atrazine occurred in three out of eight soils tested, with the greatest amount occurring i n Bravo rhizosphere soil (35% of the applied atrazine after 9 weeks). Suppression of atrazine mineralization in the Bravo rhizosphere soil did not occur with the addition of high concentrations of herbicide mixtures, but instead was increased. Plants had a positive impact on dissipation of aged atrazine in soil, with significantly less atrazine extractable from Kochia-vegetated soils than from nonvegetated soils. 11. Bacterial inoculants of forage grasses that enhance degradation of 2-chlorobenzoic acid in soil. Siciliano, S. D. and Germida, J. J. Environ toxicol chem. 16: 6 pp. 1098-1104. (June 1997). NAL Call #: QH545.A1E58 Descriptors: polluted-soils bioremediationAbstract: Biological remediation of contaminated soil is an effective method of reducing risk to human and ecosystem health. Bacteria and plants might be used to enhance remediation of soil pollutants in situ. This study assessed the potential of bacteria (12 isolates), plants (16 forage grasses), and plant-bacteria associations (selected pairings) to remediate 2-chlorobenzoic acid (2CBA)-contaminated soil. Initially, grass viability was assessed in 2CBA-contaminated soil. Soil was contaminated wi th 2CBA, forage grasses were grown under growth chamber conditions for 42 or 60 d, and the 2CBA concentration in soil was determined by gas chromatography. Only five of 16 forage grasses grew in 2CBA-treated (816 mg/kg) soil. Growth of Bromus inermis had no effect on 2CBA concentration, whereas Agropyron intermedium, B. biebersteinii, A. riparum, and Elymus dauricus decreased 2CBA relative to nonplanted control soil by 32 to 42%. The 12 bacteria isolates were screened for their ability to promote the germ ination of the five grasses in 2CBA-contaminated soil. Inoculation of A. riparum with Pseudomonas aeruginos