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Inheritance and characterization of strong resistance to phosphine in Sitophilus oryzae (L.).

Nguyen TT, Collins PJ, Ebert PR - PLoS ONE (2015)

Bottom Line: Sitophilus oryzae (Linnaeus) is a major pest of stored grain across Southeast Asia and is of increasing concern in other regions due to the advent of strong resistance to phosphine, the fumigant used to protect stored grain from pest insects.Analysis of F2 and backcross progeny indicates that two or more genes are responsible for strong resistance, and that one of these genes, designated So_rph1, not only contributes to strong resistance, but is also responsible for the weak resistance phenotype of strain QSO335.These results demonstrate that the genetic mechanism of phosphine resistance in S. oryzae is similar to that of other stored product insect pests.

View Article: PubMed Central - PubMed

Affiliation: School of Biological Sciences, University of Queensland, St. Lucia, Queensland, Australia; Faculty of Biology, Hanoi National University of Education, Hanoi, Vietnam.

ABSTRACT
Sitophilus oryzae (Linnaeus) is a major pest of stored grain across Southeast Asia and is of increasing concern in other regions due to the advent of strong resistance to phosphine, the fumigant used to protect stored grain from pest insects. We investigated the inheritance of genes controlling resistance to phosphine in a strongly resistant S. oryzae strain (NNSO7525) collected in Australia and find that the trait is autosomally inherited and incompletely recessive with a degree of dominance of -0.66. The strongly resistant strain has an LC50 52 times greater than a susceptible reference strain (LS2) and 9 times greater than a weakly resistant strain (QSO335). Analysis of F2 and backcross progeny indicates that two or more genes are responsible for strong resistance, and that one of these genes, designated So_rph1, not only contributes to strong resistance, but is also responsible for the weak resistance phenotype of strain QSO335. These results demonstrate that the genetic mechanism of phosphine resistance in S. oryzae is similar to that of other stored product insect pests. A unique observation is that a subset of the progeny of an F1 backcross generation are more strongly resistant to phosphine than the parental strongly resistant strain, which may be caused by multiple alleles of one of the resistance genes.

No MeSH data available.


Related in: MedlinePlus

Probit analysis of mortality due to phosphine exposure: W-strain x R-strain backcross.Percent mortality was determined after a 48 h exposure to phosphine at 25°C followed by a week recovery period. Results for weakly resistant (W-strain) and strongly resistant (R-strain) insects are provided for reference. Experimental data for pooled F1 progeny as well as the progeny of the backcross of the F1 to the R-strain parent are shown. A theoretical mortality response curve for the F1-BC is drawn based on the hypothesis that only a single gene contributes to the observed resistance.
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pone.0124335.g004: Probit analysis of mortality due to phosphine exposure: W-strain x R-strain backcross.Percent mortality was determined after a 48 h exposure to phosphine at 25°C followed by a week recovery period. Results for weakly resistant (W-strain) and strongly resistant (R-strain) insects are provided for reference. Experimental data for pooled F1 progeny as well as the progeny of the backcross of the F1 to the R-strain parent are shown. A theoretical mortality response curve for the F1-BC is drawn based on the hypothesis that only a single gene contributes to the observed resistance.

Mentions: To test the hypothesis that the difference between weak and strong resistance is a monogenic trait, the F1 progeny of a cross between the W-strain (♀) and the R-strain (♂) was backcrossed to the R-strain. A monogenic hypothesis predicts that half of the progeny of the F1-BC will be homozygous resistant, whereas the other half will be heterozygous for the additional gene. Thus an inflection in the response curve of the F1-BC progeny is expected at 50% mortality. A shoulder was indeed observed at 42–45% mortality (Fig 4). However, this was followed by significantly greater than expected mortality in response to 0.2 mgL-1 and 0.3 mgL-1 phosphine (P < 0.01) (S4 Table). Interestingly, a very distinct plateau occurred at 93% mortality that persisted through the highest dose tested, 0.9 mgL-1, which was highly significantly different from the value predicted from a monogenic model (P = 1.61E-08) (S4 Table). Thus, the hypothesis that one distinct gene is responsible for strong resistance compared to weak resistance is not supported by the data.


Inheritance and characterization of strong resistance to phosphine in Sitophilus oryzae (L.).

Nguyen TT, Collins PJ, Ebert PR - PLoS ONE (2015)

Probit analysis of mortality due to phosphine exposure: W-strain x R-strain backcross.Percent mortality was determined after a 48 h exposure to phosphine at 25°C followed by a week recovery period. Results for weakly resistant (W-strain) and strongly resistant (R-strain) insects are provided for reference. Experimental data for pooled F1 progeny as well as the progeny of the backcross of the F1 to the R-strain parent are shown. A theoretical mortality response curve for the F1-BC is drawn based on the hypothesis that only a single gene contributes to the observed resistance.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4401577&req=5

pone.0124335.g004: Probit analysis of mortality due to phosphine exposure: W-strain x R-strain backcross.Percent mortality was determined after a 48 h exposure to phosphine at 25°C followed by a week recovery period. Results for weakly resistant (W-strain) and strongly resistant (R-strain) insects are provided for reference. Experimental data for pooled F1 progeny as well as the progeny of the backcross of the F1 to the R-strain parent are shown. A theoretical mortality response curve for the F1-BC is drawn based on the hypothesis that only a single gene contributes to the observed resistance.
Mentions: To test the hypothesis that the difference between weak and strong resistance is a monogenic trait, the F1 progeny of a cross between the W-strain (♀) and the R-strain (♂) was backcrossed to the R-strain. A monogenic hypothesis predicts that half of the progeny of the F1-BC will be homozygous resistant, whereas the other half will be heterozygous for the additional gene. Thus an inflection in the response curve of the F1-BC progeny is expected at 50% mortality. A shoulder was indeed observed at 42–45% mortality (Fig 4). However, this was followed by significantly greater than expected mortality in response to 0.2 mgL-1 and 0.3 mgL-1 phosphine (P < 0.01) (S4 Table). Interestingly, a very distinct plateau occurred at 93% mortality that persisted through the highest dose tested, 0.9 mgL-1, which was highly significantly different from the value predicted from a monogenic model (P = 1.61E-08) (S4 Table). Thus, the hypothesis that one distinct gene is responsible for strong resistance compared to weak resistance is not supported by the data.

Bottom Line: Sitophilus oryzae (Linnaeus) is a major pest of stored grain across Southeast Asia and is of increasing concern in other regions due to the advent of strong resistance to phosphine, the fumigant used to protect stored grain from pest insects.Analysis of F2 and backcross progeny indicates that two or more genes are responsible for strong resistance, and that one of these genes, designated So_rph1, not only contributes to strong resistance, but is also responsible for the weak resistance phenotype of strain QSO335.These results demonstrate that the genetic mechanism of phosphine resistance in S. oryzae is similar to that of other stored product insect pests.

View Article: PubMed Central - PubMed

Affiliation: School of Biological Sciences, University of Queensland, St. Lucia, Queensland, Australia; Faculty of Biology, Hanoi National University of Education, Hanoi, Vietnam.

ABSTRACT
Sitophilus oryzae (Linnaeus) is a major pest of stored grain across Southeast Asia and is of increasing concern in other regions due to the advent of strong resistance to phosphine, the fumigant used to protect stored grain from pest insects. We investigated the inheritance of genes controlling resistance to phosphine in a strongly resistant S. oryzae strain (NNSO7525) collected in Australia and find that the trait is autosomally inherited and incompletely recessive with a degree of dominance of -0.66. The strongly resistant strain has an LC50 52 times greater than a susceptible reference strain (LS2) and 9 times greater than a weakly resistant strain (QSO335). Analysis of F2 and backcross progeny indicates that two or more genes are responsible for strong resistance, and that one of these genes, designated So_rph1, not only contributes to strong resistance, but is also responsible for the weak resistance phenotype of strain QSO335. These results demonstrate that the genetic mechanism of phosphine resistance in S. oryzae is similar to that of other stored product insect pests. A unique observation is that a subset of the progeny of an F1 backcross generation are more strongly resistant to phosphine than the parental strongly resistant strain, which may be caused by multiple alleles of one of the resistance genes.

No MeSH data available.


Related in: MedlinePlus