The rph1 Gene Is a Common Contributor to the Evolution of Phosphine Resistance in Independent Field Isolates of Rhyzopertha Dominica

Phosphine is the only economically viable fumigant for routine control of insect pests of stored food products, but its continued use is now threatened by the world-wide emergence of high-level resistance in key pest species. Phosphine has a unique mode of action relative to well-characterised contact pesticides. Similarly, the selective pressures that lead to resistance against field sprays differ dramatically from those encountered during fumigation. The consequences of these differences have not been investigated adequately. We determine the genetic basis of phosphine resistance in Rhyzopertha dominica strains collected from New South Wales and South Australia and compare this with resistance in a previously characterised strain from Queensland. The resistance levels range from 225 and 100 times the baseline response of a sensitive reference strain. Moreover, molecular and phenotypic data indicate that high-level resistance was derived independently in each of the three widely separated geographical regions. Despite the independent origins, resistance was due to two interacting genes in each instance. Furthermore, complementation analysis reveals that all three strains contain an incompletely recessive resistance allele of the autosomal rph1 resistance gene. This is particularly noteworthy as a resistance allele at rph1 was previously proposed to be a necessary first step in the evolution of high-level resistance. Despite the capacity of phosphine to disrupt a wide range of enzymes and biological processes, it is remarkable that the initial step in the selection of resistance is so similar in isolated outbreaks

Efficacy of Major Plant Extracts/Molecules on Field Insect Pests

Insect pests are considered the major hurdle in enhancing the production and productivity of any farming system. The use of conventional synthetic pesticides has led to the emergence of pesticide-resistant insects, environmental pollution, and negative effects on natural enemies, which have caused an ecological imbalance of the predator-prey ratio and human health hazards; therefore, eco-friendly alternative strategies are required. The plant kingdom, a rich repertoire of secondary metabolites, can be tapped as an alternative for insect pest management strategies. A number of plants have been documented to have insecticidal properties against various orders of insects in vitro by acting as antifeedants, repellents, sterilant and oviposition deterrents, etc. However, only a few plant compounds are applicable at the field level or presently commercialised. Here, we have provided an overview of the broad-spectrum insecticidal activity of plant compounds from neem, Annona, Pongamia, and Jatropha. Additionally, the impact of medicinal plants, herbs, spices, and essential oils has been reviewed briefl

Use of contraceptive methods by sexually active teenagers in Pelotas, Rio Grande do Sul State, Brazil Uso de métodos anticoncepcionais em adolescentes sexualmente ativos de 15 a 18 anos em Pelotas, Rio Grande do Sul, Brasil

This study aimed to assess the prevalence of contraceptive use by adolescents. A cross-sectional study was performed from March to September 2002 in a representative sample of adolescents 15 to 18 years of age in the urban area of Pelotas, Rio Grande do Sul State, Brazil. Multiple-stage sampling was used, and in the 448 census tracts located in the urban area, 90 were sampled and households were visited in each tract. Information was collected on sexual initiation and use of contraceptive methods. Chi-square test was used to compare proportions. The sample included 960 adolescents. 88% of subjects reported the use of any contraceptive method. Condoms were the most commonly used method (63.2%). Low adolescent schooling was the only variable associated with increased risk of non-use of contraceptives. Condom use was higher among males, adolescents whose mothers had 9 or more years of schooling, and those reporting several sexual partners in the previous year. Condoms were the most commonly used contraceptive method.<br>O estudo avaliou o uso de métodos contraceptivos em adolescentes. Entre março e setembro de 2002, realizou-se um estudo transversal na zona urbana da cidade de Pelotas, Rio Grande do Sul, Brasil. A amostragem foi em múltiplos estágios, 90 dos 448 setores censitários da zona urbana de Pelotas foram sorteados e em cada setor 86 residências foram visitadas. Considerou-se a informação do adolescente sobre a prática de relações sexuais e do uso de métodos contraceptivos. Nas comparações entre as proporções utilizou-se o teste do qui-quadrado. Foram entrevistados 960 adolescentes, enquanto que para 79 não foi possível realizar a entrevista. Aproximadamente 88% dos adolescentes usavam algum método contraceptivo. O preservativo masculino foi encontrado como o método mais usado naqueles adolescentes que têm relação sexual (63,2%). A escolaridade do adolescente foi a única variável associada com o uso de contraceptivos. O uso de preservativo masculino foi mais freqüente entre os meninos, aqueles cuja mãe tinha nove ou mais anos de escolaridade e naqueles com vários parceiros. O preservativo masculino é o método mais usado

Comparative study of in-situ catalytic pyrolysis of rice husk for syngas production: Kinetics modelling and product gas analysis

Pyrolysis of rice husk (RH) in the presence of three different types of catalysts (nickel, natural zeolite, and coal bottom ash) for syngas production were investigated by TGA-MS. The catalyst to RH ratio of 0.1 was pyrolyzed at different heating rates of 10, 20, 30, and 50 Kmin-1 in the temperature range of 323 K–1173 K. Furthermore, X-ray diffraction (XRD), Brunaur-Emmett-Teller (BET), field emission scanning electron microscope (FESEM) and X-ray fluorescence (XRF) were employed to understand the physiochemical properties and activities of the catalysts before and after pyrolysis of RH. Lastly, four different types of kinetic models such as first-order Coats-Redfern equation, Friedman, Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS) were employed to determine the activation energy (EA). The kinetic analysis revealed that the EA values reduced when catalysts were introduced into RH as compared to absence of catalysts in the pyrolysis process. The lowest EA value was attained in catalytic pyrolysis using natural zeolite (51.35–157.4 kJ/mol), followed by coal bottom ash (53.56–161.4 kJ/mol) and nickel (56.51–162.9 kJ/mol)

Phosphine resistance in India is characterised by a dihydrolipoamide dehydrogenase variant that is otherwise unobserved in eukaryotes

Phosphine (PH3) fumigation is the primary method worldwide for controlling insect pests of stored commodities. Over-reliance on phosphine, however, has led to the emergence of strong resistance. Detailed genetic studies previously identified two loci, rph1 and rph2, that interact synergistically to create a strong resistance phenotype. We compared the genetics of phosphine resistance in strains of Rhyzopertha Dominica and Tribolium castaneum from India and Australia, countries having similar pest species but widely differing in pest management practices. Sequencing analysis of the rph2 locus, dihydrolipoamide dehydrogenase (dld), identified two structurally equivalent variants, Proline49>Serine (P49S) in one R. Dominica strain and P45S in three strains of T. castaneum from India. These variants of the DLD protein likely affect FAD cofactor interaction with the enzyme. A survey of insects from storage facilities across southern India revealed that the P45/49S variant is distributed throughout the region at very high frequencies, in up to 94% of R. Dominica and 97% of T. castaneum in the state of Tamil Nadu. The abundance of the P45/49S variant in insect populations contrasted sharply with the evolutionary record in which the variant was absent from eukaryotic DLD sequences. This suggests that the variant is unlikely to provide a strong selective advantage in the absence of phosphine fumigation