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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: S-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 susceptible (S-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.g002: Probit analysis of mortality due to phosphine exposure: S-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 susceptible (S-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: The monogenic hypothesis predicts a plateau in the response curve of F1-BC at 50% mortality. However, in the backcross of F1(S-strain x R-strain) to R-strain, there was evidence for at least three plateaus appearing at mortality levels of 42%,75% and 95% instead of one plateau at 50% as expected (Fig 2). Modified chi-square values showed significant deviations across the range of tested doses at a moderately low dose (P = 0.019), moderately high doses (P = 0.040, 0.030 and 0.008) and an extremely high dose (P = 0.007) (S2 Table). Notably, observed mortality was less than expected at the moderately low dose, but greater than expected at moderately high doses. Thus, it appears that more than one factor, potentially with unequal effects, contribute to the strong resistance phenotype [25], however, this interpretation leaves the plateau at 95% mortality unexplained. The responses of the S-strain x R-strain cross and backcross progeny provide strong evidence that the monogenic hypothesis can be rejected, confirming that more than one gene controls strong resistance to phosphine.


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: S-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 susceptible (S-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.g002: Probit analysis of mortality due to phosphine exposure: S-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 susceptible (S-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: The monogenic hypothesis predicts a plateau in the response curve of F1-BC at 50% mortality. However, in the backcross of F1(S-strain x R-strain) to R-strain, there was evidence for at least three plateaus appearing at mortality levels of 42%,75% and 95% instead of one plateau at 50% as expected (Fig 2). Modified chi-square values showed significant deviations across the range of tested doses at a moderately low dose (P = 0.019), moderately high doses (P = 0.040, 0.030 and 0.008) and an extremely high dose (P = 0.007) (S2 Table). Notably, observed mortality was less than expected at the moderately low dose, but greater than expected at moderately high doses. Thus, it appears that more than one factor, potentially with unequal effects, contribute to the strong resistance phenotype [25], however, this interpretation leaves the plateau at 95% mortality unexplained. The responses of the S-strain x R-strain cross and backcross progeny provide strong evidence that the monogenic hypothesis can be rejected, confirming that more than one gene controls strong resistance to phosphine.

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