The Experts below are selected from a list of 1458 Experts worldwide ranked by ideXlab platform
Manoj K. Nayak - One of the best experts on this subject based on the ideXlab platform.
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unique genetic variants in dihydrolipoamide dehydrogenase dld gene confer strong resistance to phosphine in the rusty grain beetle Cryptolestes Ferrugineus stephens
Pesticide Biochemistry and Physiology, 2020Co-Authors: Rajeswaran Jagadeesan, Manoj K. Nayak, Virgine T Singarayan, David I Schlipalius, Nisa S Nath, Paul R. EbertAbstract:Abstract The rusty grain beetle, Cryptolestes Ferrugineus, a major pest of stored commodities, has developed very high levels (>1000×) of resistance to the fumigant phosphine. Resistance in this species is remarkably stronger than reported in any other stored product pests demanding the need to understand the molecular basis of this trait. Previous genetic studies in other grain insect pests identified specific variants in two major genes, rph1 and rph2 in conferring the strong resistance trait. However, in C. Ferrugineus, although the gene, rph1 was identified as cytochrome-b5-fatty acid desaturase, the rph2 gene has not been reported so far. We tested the candidate gene for rph2, dihydrolipoamide dehydrogenase (dld) using the recently published transcriptome of C. Ferrugineus and identified three variants, L73N and A355G + D360H, a haplotype, conferring resistance in this species. Our sequence analysis in resistant strain and phosphine selected resistant survivors indicates that these variants occur either alone as a homozygote or a mixture of heterozygotes (i.e complex heterozygotes) both conferring strong resistance. We also found that one of the three variants, possibly L73N expressing “dominant” trait at low frequency in resistant insects. Comparison of dld sequences between Australian and Chinese resistant strain of this species confirmed that the identified variants are highly conserved. Our fitness analysis indicated that resistant insects may not incur significant biological costs in the absence of phosphine selection for 19 generations. Thus, we propose that the observed high levels of resistance in C. Ferrugineus could be primarily due to the characteristics of three unique variants, L73N and A355G + D360H within dld.
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Co-fumigation with phosphine and sulfuryl fluoride: Potential for managing strongly phosphine-resistant rusty grain beetle, Cryptolestes Ferrugineus (Stephens):
Julius-Kühn-Archiv, 2018Co-Authors: Jagadeesan Rajeswaran, Manoj K. Nayak, Virgine T Singarayan, Paul R. EbertAbstract:Populations of rusty grain beetle, Cryptolestes Ferrugineus, have developed a very high level of resistance (1300×) to the fumigant phosphine (PH3) in Australia. Resistant insects triggered control failures, threatening the country’s annual grain market worth AU$8 billion. Although PH3 protocols were amended to manage this new resistance, fumigation requires lengthy exposure periods which has practical difficulties. While there is no suitable replacement for PH3, the current study explores potential approaches to enhance the efficacy of this fumigant. One possibility is co-fumigation of PH3 with another complementary fumigant, sulfuryl fluoride (SO2F2 or SF), with the dual goals: enhanced efficacy and minimise use of both fumigants. A cohort of mixed age eggs and adults of PH3-resistant C. Ferrugineus was fumigated with PH3 and SF individually, as well as in combination inside desiccators at 25°C and 60%RH for 168 h. Two doses below the maximal registered rates for SF (8.9 mg L- 1, equivalent to 1500 g hm-3) and PH3 (1.0 mg L-1) were tested. Co-fumigation was performed simultaneously for 168 h. Our results revealed that, the mixture of 1.1 mg L-1 or 2.2 mg L-1 of SF and 0.5 mg L-1 of PH3 over 168 h achieved complete control against resistant C. Ferrugineus eggs and adults, whereas each of the tested doses failed individually. Our study confirms that SF and PH3 enhance the efficacy of each other when used in combination, which holds great potential for managing resistant C. Ferrugineus.
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Relative tolerance and expression of resistance to phosphine in life stages of the rusty grain beetle, Cryptolestes Ferrugineus
Journal of Pest Science, 2018Co-Authors: Muralitharan Venkidusamy, Manoj K. Nayak, Rajeswaran Jagadeesan, Mohankumar Subbarayalu, Chandrasekaran Subramaniam, Patrick J. CollinsAbstract:Cryptolestes Ferrugineus is a serious cosmopolitan pest of stored products. Frequent and indiscriminate usage of phosphine has caused the development of high levels of resistance to this fumigant. As there are few alternatives, it is imperative that resistance to phosphine is managed. Effective management requires knowledge of key factors driving the rate of selection. One of the most important factors is the response of each resistance genotype to phosphine, especially heterozygotes. Moreover, it is important to understand the expression of resistance in all life stages as all stages are subjected to selection during fumigation. We determined the relative tolerance and resistance levels to phosphine in all life stages of homozygous parental strains (susceptible and resistant) and their F_1 progeny (heterozygous) and estimated relative dominance of resistance within life stages over 48 h. In susceptible insects, relative tolerance was highest in eggs followed by pupae, then adults which had about the same tolerance as larvae. In homozygous resistant insects, the order of tolerance was adult = egg > pupae > larvae and in heterozygotes larvae > eggs > pupae > adults. All life stages expressed resistance with resistance ratios highest in adults > pupae > larvae > eggs. At LC_50, resistance was incompletely recessive in eggs, pupae and adults and incompletely dominant in larvae. Eggs and adults were also incompletely recessive at LC_95, but larvae were completely dominant and pupae were incompletely dominant. Our data showed that a proportion of heterozygotes in all life stages, the major carriers of resistance in the field, will survive at very high concentrations, particularly in the egg stage, forming a nucleus for reinfestation or dispersal of resistance.
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Integrated approach to manage strong resistance to phosphine (PH3) in rusty grain beetle, Cryptolestes Ferrugineus
2017Co-Authors: Rajeswaran Jagadeesan, Gregory J. Daglish, Hervoika Pavic, Paul R. Ebert, Manoj K. NayakAbstract:Populations of rusty grain beetle, Cryptolestes Ferrugineus, a cosmopolitan grain insect pest, have recently developed a very high-level of resistance (1300×) to fumigant phosphine in Australia, threatening the country’s international grain market worth of 8 billion per year. Due to the failure of the registered rates of phosphine, industry urgently needed alternative strategies to manage this new resistance. To address this, an integrated resistance management strategy (IRM) was developed with three core components: 1. regular monitoring and characterization of resistance, 2. developing effective phosphine protocols, and 3. exploring alternative fumigants and treatments. Resistance was monitored across Australia in pest samples collected from farms and centrals storages using a modified FAO method as well as quick knockdown tests. Our results indicated that high-level resistance in C. Ferrugineus is prevalent in eastern Australia, particularly in Queensland and New South Wales, particularly in the bulk handing sector. Time to population extinction was assessed in field-derived reference resistant strains using higher dosages (c) and exposure times (t) and the effective c x t regimes were validated in the field for the use by the grain industry. A phosphine concentration of 720 ppm (1 mg L-1) over 18 days was found to be effective in controlling all life stages of phosphine-resistant C. Ferrugineus at 25°C. In a parallel research, the suitability of sulfuryl fluoride (ProfumeTM), as an alternative fumigant to phosphine was assessed through laboratory and field efficacy trials. Our results showed that phosphine-resistant insects are highly susceptible to sulfuryl fluoride and a CT of 750 g hm-3 (5.2 mg L-1) over 6 days at 25˚C would be sufficient against all phosphine-resistant pests including C. Ferrugineus. While sulfuryl fluoride has promising potential as a “phosphine resistance breaker” the team is currently exploring ways of co-treating phosphine and sulfuryl fluoride, in order to reduce the overall selection pressure against these two fumigants in insects.
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Genetic characterization of field-evolved resistance to phosphine in the rusty grain beetle, Cryptolestes Ferrugineus (Laemophloeidae: Coleoptera)
Pesticide biochemistry and physiology, 2015Co-Authors: Rajeswaran Jagadeesan, Manoj K. Nayak, Patrick J. Collins, David I Schlipalius, Paul R. EbertAbstract:Inheritance of resistance to phosphine fumigant was investigated in three field-collected strains of rusty grain beetle, Cryptolestes Ferrugineus, Susceptible (S-strain), Weakly Resistant (Weak-R) and Strongly Resistant (Strong-R). The strains were purified for susceptibility, weak resistance and strong resistance to phosphine, respectively, to ensure homozygosity of resistance genotype. Crosses were established between S-strain×Weak-R, S-strain×Strong-R and Weak-R×Strong-R, and the dose mortality responses to phosphine of these strains and their F1, F2 and F1-backcross progeny were obtained. The fumigations were undertaken at 25°C and 55% RH for 72h. Weak-R and Strong-R showed resistance factors of 6.3× and 505× compared with S-strain at the LC50. Both weak and strong resistances were expressed as incompletely recessive with degrees of dominance of -0.48 and -0.43 at the LC50, respectively. Responses of F2 and F1-backcross progeny indicated the existence of one major gene in Weak-R, and at least two major genes in Strong-R, one of which was allelic with the major factor in Weak-R. Phenotypic variance analyses also estimated that the number of independently segregating genes conferring weak resistance was 1 (nE=0.89) whereas there were two genes controlling strong resistance (nE=1.2). The second gene, unique to Strong-R, interacted synergistically with the first gene to confer a very high level of resistance (~80×). Neither of the two major resistance genes was sex linked. Despite the similarity of the genetics of resistance to that previously observed in other pest species, a significant proportion (~15 to 30%) of F1 individuals survived at phosphine concentrations higher than predicted. Thus it is likely that additional dominant heritable factors, present in some individuals in the population, also influenced the resistance phenotype. Our results will help in understanding the process of selection for phosphine resistance in the field which will inform resistance management strategies. In addition, this information will provide a basis for the identification of the resistance genes.
Paul R. Ebert - One of the best experts on this subject based on the ideXlab platform.
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unique genetic variants in dihydrolipoamide dehydrogenase dld gene confer strong resistance to phosphine in the rusty grain beetle Cryptolestes Ferrugineus stephens
Pesticide Biochemistry and Physiology, 2020Co-Authors: Rajeswaran Jagadeesan, Manoj K. Nayak, Virgine T Singarayan, David I Schlipalius, Nisa S Nath, Paul R. EbertAbstract:Abstract The rusty grain beetle, Cryptolestes Ferrugineus, a major pest of stored commodities, has developed very high levels (>1000×) of resistance to the fumigant phosphine. Resistance in this species is remarkably stronger than reported in any other stored product pests demanding the need to understand the molecular basis of this trait. Previous genetic studies in other grain insect pests identified specific variants in two major genes, rph1 and rph2 in conferring the strong resistance trait. However, in C. Ferrugineus, although the gene, rph1 was identified as cytochrome-b5-fatty acid desaturase, the rph2 gene has not been reported so far. We tested the candidate gene for rph2, dihydrolipoamide dehydrogenase (dld) using the recently published transcriptome of C. Ferrugineus and identified three variants, L73N and A355G + D360H, a haplotype, conferring resistance in this species. Our sequence analysis in resistant strain and phosphine selected resistant survivors indicates that these variants occur either alone as a homozygote or a mixture of heterozygotes (i.e complex heterozygotes) both conferring strong resistance. We also found that one of the three variants, possibly L73N expressing “dominant” trait at low frequency in resistant insects. Comparison of dld sequences between Australian and Chinese resistant strain of this species confirmed that the identified variants are highly conserved. Our fitness analysis indicated that resistant insects may not incur significant biological costs in the absence of phosphine selection for 19 generations. Thus, we propose that the observed high levels of resistance in C. Ferrugineus could be primarily due to the characteristics of three unique variants, L73N and A355G + D360H within dld.
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Co-fumigation with phosphine and sulfuryl fluoride: Potential for managing strongly phosphine-resistant rusty grain beetle, Cryptolestes Ferrugineus (Stephens):
Julius-Kühn-Archiv, 2018Co-Authors: Jagadeesan Rajeswaran, Manoj K. Nayak, Virgine T Singarayan, Paul R. EbertAbstract:Populations of rusty grain beetle, Cryptolestes Ferrugineus, have developed a very high level of resistance (1300×) to the fumigant phosphine (PH3) in Australia. Resistant insects triggered control failures, threatening the country’s annual grain market worth AU$8 billion. Although PH3 protocols were amended to manage this new resistance, fumigation requires lengthy exposure periods which has practical difficulties. While there is no suitable replacement for PH3, the current study explores potential approaches to enhance the efficacy of this fumigant. One possibility is co-fumigation of PH3 with another complementary fumigant, sulfuryl fluoride (SO2F2 or SF), with the dual goals: enhanced efficacy and minimise use of both fumigants. A cohort of mixed age eggs and adults of PH3-resistant C. Ferrugineus was fumigated with PH3 and SF individually, as well as in combination inside desiccators at 25°C and 60%RH for 168 h. Two doses below the maximal registered rates for SF (8.9 mg L- 1, equivalent to 1500 g hm-3) and PH3 (1.0 mg L-1) were tested. Co-fumigation was performed simultaneously for 168 h. Our results revealed that, the mixture of 1.1 mg L-1 or 2.2 mg L-1 of SF and 0.5 mg L-1 of PH3 over 168 h achieved complete control against resistant C. Ferrugineus eggs and adults, whereas each of the tested doses failed individually. Our study confirms that SF and PH3 enhance the efficacy of each other when used in combination, which holds great potential for managing resistant C. Ferrugineus.
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Integrated approach to manage strong resistance to phosphine (PH3) in rusty grain beetle, Cryptolestes Ferrugineus
2017Co-Authors: Rajeswaran Jagadeesan, Gregory J. Daglish, Hervoika Pavic, Paul R. Ebert, Manoj K. NayakAbstract:Populations of rusty grain beetle, Cryptolestes Ferrugineus, a cosmopolitan grain insect pest, have recently developed a very high-level of resistance (1300×) to fumigant phosphine in Australia, threatening the country’s international grain market worth of 8 billion per year. Due to the failure of the registered rates of phosphine, industry urgently needed alternative strategies to manage this new resistance. To address this, an integrated resistance management strategy (IRM) was developed with three core components: 1. regular monitoring and characterization of resistance, 2. developing effective phosphine protocols, and 3. exploring alternative fumigants and treatments. Resistance was monitored across Australia in pest samples collected from farms and centrals storages using a modified FAO method as well as quick knockdown tests. Our results indicated that high-level resistance in C. Ferrugineus is prevalent in eastern Australia, particularly in Queensland and New South Wales, particularly in the bulk handing sector. Time to population extinction was assessed in field-derived reference resistant strains using higher dosages (c) and exposure times (t) and the effective c x t regimes were validated in the field for the use by the grain industry. A phosphine concentration of 720 ppm (1 mg L-1) over 18 days was found to be effective in controlling all life stages of phosphine-resistant C. Ferrugineus at 25°C. In a parallel research, the suitability of sulfuryl fluoride (ProfumeTM), as an alternative fumigant to phosphine was assessed through laboratory and field efficacy trials. Our results showed that phosphine-resistant insects are highly susceptible to sulfuryl fluoride and a CT of 750 g hm-3 (5.2 mg L-1) over 6 days at 25˚C would be sufficient against all phosphine-resistant pests including C. Ferrugineus. While sulfuryl fluoride has promising potential as a “phosphine resistance breaker” the team is currently exploring ways of co-treating phosphine and sulfuryl fluoride, in order to reduce the overall selection pressure against these two fumigants in insects.
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Genetic characterization of field-evolved resistance to phosphine in the rusty grain beetle, Cryptolestes Ferrugineus (Laemophloeidae: Coleoptera)
Pesticide biochemistry and physiology, 2015Co-Authors: Rajeswaran Jagadeesan, Manoj K. Nayak, Patrick J. Collins, David I Schlipalius, Paul R. EbertAbstract:Inheritance of resistance to phosphine fumigant was investigated in three field-collected strains of rusty grain beetle, Cryptolestes Ferrugineus, Susceptible (S-strain), Weakly Resistant (Weak-R) and Strongly Resistant (Strong-R). The strains were purified for susceptibility, weak resistance and strong resistance to phosphine, respectively, to ensure homozygosity of resistance genotype. Crosses were established between S-strain×Weak-R, S-strain×Strong-R and Weak-R×Strong-R, and the dose mortality responses to phosphine of these strains and their F1, F2 and F1-backcross progeny were obtained. The fumigations were undertaken at 25°C and 55% RH for 72h. Weak-R and Strong-R showed resistance factors of 6.3× and 505× compared with S-strain at the LC50. Both weak and strong resistances were expressed as incompletely recessive with degrees of dominance of -0.48 and -0.43 at the LC50, respectively. Responses of F2 and F1-backcross progeny indicated the existence of one major gene in Weak-R, and at least two major genes in Strong-R, one of which was allelic with the major factor in Weak-R. Phenotypic variance analyses also estimated that the number of independently segregating genes conferring weak resistance was 1 (nE=0.89) whereas there were two genes controlling strong resistance (nE=1.2). The second gene, unique to Strong-R, interacted synergistically with the first gene to confer a very high level of resistance (~80×). Neither of the two major resistance genes was sex linked. Despite the similarity of the genetics of resistance to that previously observed in other pest species, a significant proportion (~15 to 30%) of F1 individuals survived at phosphine concentrations higher than predicted. Thus it is likely that additional dominant heritable factors, present in some individuals in the population, also influenced the resistance phenotype. Our results will help in understanding the process of selection for phosphine resistance in the field which will inform resistance management strategies. In addition, this information will provide a basis for the identification of the resistance genes.
Noel D.g. White - One of the best experts on this subject based on the ideXlab platform.
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A new method to rapidly detect rusty grain beetle, Cryptolestes Ferrugineus (Stephens), in stored grain
Journal of Stored Products Research, 2015Co-Authors: Fuji Jian, Digvir S. Jayas, Paul G. Fields, Noel D.g. WhiteAbstract:Abstract Information on insect infestation inside stored grain bulks is required for safe grain storage. A new method to rapidly detect both adults and larvae of Cryptolestes Ferrugineus (Stephens) in grain was developed based on the principle of microwave heating and insect behaviour under elevated temperature. The designed apparatus and processing procedure were tested to extract both the adults and larvae inside wheat with 14%, 16% and 18% moisture contents by using a domestic microwave oven (referred to as the microwave method). The recovery percentage of the introduced insects associated with the microwave method was compared with that of the Berlese funnel method (810 cm 3 wheat in a funnel under an incandescent light bulb). The microwave method recovered 97.8% of introduced adults, while 90.6% of adults were recovered by the Berlese funnel method. The recovery percentage of the larvae inside marked wheat kernels was 83.3 ± 3.3% with the microwave method and less than 27% with the Berlese funnel method. There was no significant difference in extraction percentage between old and young larvae when the microwave method was used. The moisture content of the treated grain did not significantly influence the extraction percentage of the pest insect. The total processing time of the microwave method was less than 30 min compared to 6 h required for the Berlese funnel method.
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Movement of Cryptolestes Ferrugineus out of wheat kernels and their mortalities under elevated temperatures
Journal of Stored Products Research, 2014Co-Authors: G.d. Arlene-christina, Digvir S. Jayas, Noel D.g. White, Fuji Jian, Paul G. Fields, K. AlagusundaramAbstract:Abstract The rusty grain beetle, Cryptolestes Ferrugineus (Coleoptera: Laemophloeidae), is a common pest in stored grain. The present study examined the time taken for larvae of C. Ferrugineus to exit wheat kernels at 40–55 °C, stage-specific mortality at 40–60 °C, and whether a combination of heat and shaking could be used to control this pest. The average time larvae took to leave wheat kernels ranged from 130 min at 40 °C to 6 min at 55 °C. At 55 °C and 6 min exposure, 81 ± 2% of larvae exited the kernels, 10 ± 1% of larvae were alive inside kernels and 9 ± 2% were dead inside kernels. Under constant temperature of 55 °C, less than 5% of the larvae escaped in 2 min, but under the rising temperature of 40, 45, 50 and then to 55 °C, over 50% of the larvae escaped in 2 min at 55 °C. The time taken to reach 50 and 95% mortality was similar for all stages. Higher temperatures resulted in higher mortality in a shorter exposure time. The longest LT 95 for pupae was 6480, 293, 50 and 3.7 min at 45, 50, 55 and 60 °C, respectively. At 55 °C for 88 min, combined with shaking gave 88% control in a 100-g wheat bulk. Time needed to kill eggs and pupae were much longer than the time needed to force larvae out of kernels. Therefore, the combination of heat and shaking would only provide partial disinfestation of C. Ferrugineus .
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Three-dimensional spatial distribution of adults of Cryptolestes Ferrugineus (Coleoptera: Laemophloeidae) in stored wheat under different temperatures, moisture contents, and adult densities
Journal of Stored Products Research, 2011Co-Authors: Fuji Jian, Digvir S. Jayas, Ron Larson, Noel D.g. WhiteAbstract:Abstract Spatial and temporal distributions of adults of Cryptolestes Ferrugineus in stored wheat were determined in a 1.5 t bin of wheat held at 20, 25 and 30 °C and 11%, 13% and 15% grain moisture contents (wet basis). The introduced insect densities were 0.1 (low), 1.0 (medium), and 10.0 (high) adults/kg wheat and the 1.5 t of wheat was sampled at 5 locations with 45 kg in a sample unit (referred to as primary unit, about 15% of the wheat was sampled). At each location, the 45 kg sample unit was separated into three 15 kg vertical layers (referred to as subunits). Geostatistical analysis showed that: 1) insect numbers at medium or high density and in the vertical direction were better correlated than that at low insect density and in the horizontal direction, respectively; 2) this correlation decreased with increasing grain temperatures; and 3) the temporal continuous property might not exist or there was a weak temporal continuity. Aggregation was the highest at the low insect density and then decreased with the increase of insect density due to a repelling effect amongst adults at high insect density. The normal distribution model was appropriate for the description of the count frequency in 32 out of 36 sampling sets (88.9%) when 15 kg subunit data were used. In addition, adults of C. Ferrugineus had clumped distribution about 95% of the time and uniform dispersion about 5% of the time. This is the first research illustrating the spatial and temporal distributions of adult C. Ferrugineus using large sample units and known insect densities.
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Thermal imaging to detect infestation by Cryptolestes Ferrugineus inside wheat kernels
Journal of Stored Products Research, 2008Co-Authors: Annamalai Manickavasagan, Digvir S. Jayas, Noel D.g. WhiteAbstract:Abstract Canada's zero tolerance for live insects in grain received from farmers, and shipped to domestic and export buyers, has necessitated the development of an accurate insect detection method. An infrared thermal imaging system was developed to detect infestation by six developmental stages (four larval instars, pupae and adults) of Cryptolestes Ferrugineus under the seed coat on the germ of the wheat kernels. The artificially infested wheat kernels were removed from the incubation room (30 °C), refrigerated (5 °C) for 60 s, maintained at ambient conditions for 20 s, and imaged using a thermal camera to identify each developmental stage ( n =283). The means of the highest 5% and 10% of all temperature values on the surface of the grain were significantly higher ( α =0.05) for grains having young larvae inside and lower for grains having pupae inside. Temperature distribution on the surface of the infested kernels with different stages of C. Ferrugineus was highly correlated with the respiration rate of each developmental stage ( r =0.83–0.91). The overall classification accuracy for a quadratic function was 83.5% and 77.7% for infested and sound kernels, respectively, and for a linear function, it was 77.6% and 83.0% for infested and sound kernels, respectively, in pairwise discriminations. Thermal imaging has the potential to identify whether the grain is infested or not, but is less effective in identifying which developmental stage is present.
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Two-dimensional diffusion of Cryptolestes Ferrugineus (Stephens) (Coleoptera: Laemophloeidae) populations in stored wheat under constant environmental conditions
Journal of Stored Products Research, 2007Co-Authors: Fuji Jian, Digvir S. Jayas, Noel D.g. White, Edward A. SmithAbstract:Abstract Insect movement inside a stored-grain bulk increases the chance for the pests to find biologically suitable locations for their development and multiplication. The movement of rusty grain beetle, Cryptolestes Ferrugineus, adults was determined in a 0.1×1×1 m wooden box filled with wheat. There were 12 combinations of temperature (20, 25, 30, or 35 °C), number of adults (125, 250, or 500), moisture content (12.5, 14.5, or 16.5%), and time periods (3, 6, 12, 24 or 72 h) over which movement could occur. The diffusivities in each set of environmental conditions were calculated using a developed procedure (program) and experimental data. The diffusivity at 14.5% m.c. and 20 °C in the 24 h movement period was 2.5±0.3×10 −4 m 2 /h. The diffusivity increased with increasing temperature, decreasing moisture contents, decreasing movement periods, and increasing insect numbers. Adult numbers in each section of the wooden box were predicted using an analytical model and calculated diffusivities. There were no significant differences between measured and predicted adult numbers. This research suggests that distribution and dispersal of the C. Ferrugineus adults in stored wheat follow a diffusion pattern under constant environmental conditions.
Patrick J. Collins - One of the best experts on this subject based on the ideXlab platform.
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Relative tolerance and expression of resistance to phosphine in life stages of the rusty grain beetle, Cryptolestes Ferrugineus
Journal of Pest Science, 2018Co-Authors: Muralitharan Venkidusamy, Manoj K. Nayak, Rajeswaran Jagadeesan, Mohankumar Subbarayalu, Chandrasekaran Subramaniam, Patrick J. CollinsAbstract:Cryptolestes Ferrugineus is a serious cosmopolitan pest of stored products. Frequent and indiscriminate usage of phosphine has caused the development of high levels of resistance to this fumigant. As there are few alternatives, it is imperative that resistance to phosphine is managed. Effective management requires knowledge of key factors driving the rate of selection. One of the most important factors is the response of each resistance genotype to phosphine, especially heterozygotes. Moreover, it is important to understand the expression of resistance in all life stages as all stages are subjected to selection during fumigation. We determined the relative tolerance and resistance levels to phosphine in all life stages of homozygous parental strains (susceptible and resistant) and their F_1 progeny (heterozygous) and estimated relative dominance of resistance within life stages over 48 h. In susceptible insects, relative tolerance was highest in eggs followed by pupae, then adults which had about the same tolerance as larvae. In homozygous resistant insects, the order of tolerance was adult = egg > pupae > larvae and in heterozygotes larvae > eggs > pupae > adults. All life stages expressed resistance with resistance ratios highest in adults > pupae > larvae > eggs. At LC_50, resistance was incompletely recessive in eggs, pupae and adults and incompletely dominant in larvae. Eggs and adults were also incompletely recessive at LC_95, but larvae were completely dominant and pupae were incompletely dominant. Our data showed that a proportion of heterozygotes in all life stages, the major carriers of resistance in the field, will survive at very high concentrations, particularly in the egg stage, forming a nucleus for reinfestation or dispersal of resistance.
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Genetic characterization of field-evolved resistance to phosphine in the rusty grain beetle, Cryptolestes Ferrugineus (Laemophloeidae: Coleoptera)
Pesticide biochemistry and physiology, 2015Co-Authors: Rajeswaran Jagadeesan, Manoj K. Nayak, Patrick J. Collins, David I Schlipalius, Paul R. EbertAbstract:Inheritance of resistance to phosphine fumigant was investigated in three field-collected strains of rusty grain beetle, Cryptolestes Ferrugineus, Susceptible (S-strain), Weakly Resistant (Weak-R) and Strongly Resistant (Strong-R). The strains were purified for susceptibility, weak resistance and strong resistance to phosphine, respectively, to ensure homozygosity of resistance genotype. Crosses were established between S-strain×Weak-R, S-strain×Strong-R and Weak-R×Strong-R, and the dose mortality responses to phosphine of these strains and their F1, F2 and F1-backcross progeny were obtained. The fumigations were undertaken at 25°C and 55% RH for 72h. Weak-R and Strong-R showed resistance factors of 6.3× and 505× compared with S-strain at the LC50. Both weak and strong resistances were expressed as incompletely recessive with degrees of dominance of -0.48 and -0.43 at the LC50, respectively. Responses of F2 and F1-backcross progeny indicated the existence of one major gene in Weak-R, and at least two major genes in Strong-R, one of which was allelic with the major factor in Weak-R. Phenotypic variance analyses also estimated that the number of independently segregating genes conferring weak resistance was 1 (nE=0.89) whereas there were two genes controlling strong resistance (nE=1.2). The second gene, unique to Strong-R, interacted synergistically with the first gene to confer a very high level of resistance (~80×). Neither of the two major resistance genes was sex linked. Despite the similarity of the genetics of resistance to that previously observed in other pest species, a significant proportion (~15 to 30%) of F1 individuals survived at phosphine concentrations higher than predicted. Thus it is likely that additional dominant heritable factors, present in some individuals in the population, also influenced the resistance phenotype. Our results will help in understanding the process of selection for phosphine resistance in the field which will inform resistance management strategies. In addition, this information will provide a basis for the identification of the resistance genes.
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Strong resistance to phosphine in the rusty grain beetle, Cryptolestes Ferrugineus (Stephens) (Coleoptera: Laemophloeidae): its characterisation, a rapid assay for diagnosis and its distribution in Australia
Pest management science, 2012Co-Authors: Manoj K. Nayak, Joanne C. Holloway, Robert N. Emery, Hervoika Pavic, Justin Bartlet, Patrick J. CollinsAbstract:BACKGROUND: The recent development of very high resistance to phosphine in rusty grain beetle, Cryptolestes Ferrugineus (Stephens), seriously threatens stored-grain biosecurity. The aim was to characterise this resistance, to develop a rapid bioassay for its diagnosis to support pest management and to document the distribution of resistance in Australia in 20072011. RESULTS: Bioassays of purified laboratory reference strains and field-collected samples revealed three phenotypes: susceptible, weakly resistant and strongly resistant. With resistance factors of > 1000 x , resistance to phosphine expressed by the strong resistance phenotype was higher than reported for any stored-product insect species. The new time-to-knockdown assay rapidly and accurately diagnosed each resistance phenotype within 6 h. Although less frequent in western Australia, weak resistance was detected throughout all grain production regions. Strong resistance occurred predominantly in central storages in eastern Australia. CONCLUSION: Resistance to phosphine in the rusty grain beetle is expressed through two identifiable phenotypes: weak and strong. Strong resistance requires urgent changes to current fumigation dosages. The development of a rapid assay for diagnosis of resistance enables the provision of same-day advice to expedite resistance management decisions. (c) 2012 Commonwealth of Australia. Published by John Wiley & Sons, Ltd.
Rajeswaran Jagadeesan - One of the best experts on this subject based on the ideXlab platform.
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unique genetic variants in dihydrolipoamide dehydrogenase dld gene confer strong resistance to phosphine in the rusty grain beetle Cryptolestes Ferrugineus stephens
Pesticide Biochemistry and Physiology, 2020Co-Authors: Rajeswaran Jagadeesan, Manoj K. Nayak, Virgine T Singarayan, David I Schlipalius, Nisa S Nath, Paul R. EbertAbstract:Abstract The rusty grain beetle, Cryptolestes Ferrugineus, a major pest of stored commodities, has developed very high levels (>1000×) of resistance to the fumigant phosphine. Resistance in this species is remarkably stronger than reported in any other stored product pests demanding the need to understand the molecular basis of this trait. Previous genetic studies in other grain insect pests identified specific variants in two major genes, rph1 and rph2 in conferring the strong resistance trait. However, in C. Ferrugineus, although the gene, rph1 was identified as cytochrome-b5-fatty acid desaturase, the rph2 gene has not been reported so far. We tested the candidate gene for rph2, dihydrolipoamide dehydrogenase (dld) using the recently published transcriptome of C. Ferrugineus and identified three variants, L73N and A355G + D360H, a haplotype, conferring resistance in this species. Our sequence analysis in resistant strain and phosphine selected resistant survivors indicates that these variants occur either alone as a homozygote or a mixture of heterozygotes (i.e complex heterozygotes) both conferring strong resistance. We also found that one of the three variants, possibly L73N expressing “dominant” trait at low frequency in resistant insects. Comparison of dld sequences between Australian and Chinese resistant strain of this species confirmed that the identified variants are highly conserved. Our fitness analysis indicated that resistant insects may not incur significant biological costs in the absence of phosphine selection for 19 generations. Thus, we propose that the observed high levels of resistance in C. Ferrugineus could be primarily due to the characteristics of three unique variants, L73N and A355G + D360H within dld.
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Relative tolerance and expression of resistance to phosphine in life stages of the rusty grain beetle, Cryptolestes Ferrugineus
Journal of Pest Science, 2018Co-Authors: Muralitharan Venkidusamy, Manoj K. Nayak, Rajeswaran Jagadeesan, Mohankumar Subbarayalu, Chandrasekaran Subramaniam, Patrick J. CollinsAbstract:Cryptolestes Ferrugineus is a serious cosmopolitan pest of stored products. Frequent and indiscriminate usage of phosphine has caused the development of high levels of resistance to this fumigant. As there are few alternatives, it is imperative that resistance to phosphine is managed. Effective management requires knowledge of key factors driving the rate of selection. One of the most important factors is the response of each resistance genotype to phosphine, especially heterozygotes. Moreover, it is important to understand the expression of resistance in all life stages as all stages are subjected to selection during fumigation. We determined the relative tolerance and resistance levels to phosphine in all life stages of homozygous parental strains (susceptible and resistant) and their F_1 progeny (heterozygous) and estimated relative dominance of resistance within life stages over 48 h. In susceptible insects, relative tolerance was highest in eggs followed by pupae, then adults which had about the same tolerance as larvae. In homozygous resistant insects, the order of tolerance was adult = egg > pupae > larvae and in heterozygotes larvae > eggs > pupae > adults. All life stages expressed resistance with resistance ratios highest in adults > pupae > larvae > eggs. At LC_50, resistance was incompletely recessive in eggs, pupae and adults and incompletely dominant in larvae. Eggs and adults were also incompletely recessive at LC_95, but larvae were completely dominant and pupae were incompletely dominant. Our data showed that a proportion of heterozygotes in all life stages, the major carriers of resistance in the field, will survive at very high concentrations, particularly in the egg stage, forming a nucleus for reinfestation or dispersal of resistance.
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Integrated approach to manage strong resistance to phosphine (PH3) in rusty grain beetle, Cryptolestes Ferrugineus
2017Co-Authors: Rajeswaran Jagadeesan, Gregory J. Daglish, Hervoika Pavic, Paul R. Ebert, Manoj K. NayakAbstract:Populations of rusty grain beetle, Cryptolestes Ferrugineus, a cosmopolitan grain insect pest, have recently developed a very high-level of resistance (1300×) to fumigant phosphine in Australia, threatening the country’s international grain market worth of 8 billion per year. Due to the failure of the registered rates of phosphine, industry urgently needed alternative strategies to manage this new resistance. To address this, an integrated resistance management strategy (IRM) was developed with three core components: 1. regular monitoring and characterization of resistance, 2. developing effective phosphine protocols, and 3. exploring alternative fumigants and treatments. Resistance was monitored across Australia in pest samples collected from farms and centrals storages using a modified FAO method as well as quick knockdown tests. Our results indicated that high-level resistance in C. Ferrugineus is prevalent in eastern Australia, particularly in Queensland and New South Wales, particularly in the bulk handing sector. Time to population extinction was assessed in field-derived reference resistant strains using higher dosages (c) and exposure times (t) and the effective c x t regimes were validated in the field for the use by the grain industry. A phosphine concentration of 720 ppm (1 mg L-1) over 18 days was found to be effective in controlling all life stages of phosphine-resistant C. Ferrugineus at 25°C. In a parallel research, the suitability of sulfuryl fluoride (ProfumeTM), as an alternative fumigant to phosphine was assessed through laboratory and field efficacy trials. Our results showed that phosphine-resistant insects are highly susceptible to sulfuryl fluoride and a CT of 750 g hm-3 (5.2 mg L-1) over 6 days at 25˚C would be sufficient against all phosphine-resistant pests including C. Ferrugineus. While sulfuryl fluoride has promising potential as a “phosphine resistance breaker” the team is currently exploring ways of co-treating phosphine and sulfuryl fluoride, in order to reduce the overall selection pressure against these two fumigants in insects.
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Genetic characterization of field-evolved resistance to phosphine in the rusty grain beetle, Cryptolestes Ferrugineus (Laemophloeidae: Coleoptera)
Pesticide biochemistry and physiology, 2015Co-Authors: Rajeswaran Jagadeesan, Manoj K. Nayak, Patrick J. Collins, David I Schlipalius, Paul R. EbertAbstract:Inheritance of resistance to phosphine fumigant was investigated in three field-collected strains of rusty grain beetle, Cryptolestes Ferrugineus, Susceptible (S-strain), Weakly Resistant (Weak-R) and Strongly Resistant (Strong-R). The strains were purified for susceptibility, weak resistance and strong resistance to phosphine, respectively, to ensure homozygosity of resistance genotype. Crosses were established between S-strain×Weak-R, S-strain×Strong-R and Weak-R×Strong-R, and the dose mortality responses to phosphine of these strains and their F1, F2 and F1-backcross progeny were obtained. The fumigations were undertaken at 25°C and 55% RH for 72h. Weak-R and Strong-R showed resistance factors of 6.3× and 505× compared with S-strain at the LC50. Both weak and strong resistances were expressed as incompletely recessive with degrees of dominance of -0.48 and -0.43 at the LC50, respectively. Responses of F2 and F1-backcross progeny indicated the existence of one major gene in Weak-R, and at least two major genes in Strong-R, one of which was allelic with the major factor in Weak-R. Phenotypic variance analyses also estimated that the number of independently segregating genes conferring weak resistance was 1 (nE=0.89) whereas there were two genes controlling strong resistance (nE=1.2). The second gene, unique to Strong-R, interacted synergistically with the first gene to confer a very high level of resistance (~80×). Neither of the two major resistance genes was sex linked. Despite the similarity of the genetics of resistance to that previously observed in other pest species, a significant proportion (~15 to 30%) of F1 individuals survived at phosphine concentrations higher than predicted. Thus it is likely that additional dominant heritable factors, present in some individuals in the population, also influenced the resistance phenotype. Our results will help in understanding the process of selection for phosphine resistance in the field which will inform resistance management strategies. In addition, this information will provide a basis for the identification of the resistance genes.