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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 intercross.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 reciprocal F1 and F2 progeny are shown. A theoretical mortality response curve for the F2 is drawn based on the hypothesis that only a single gene contributes to the observed resistance.
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pone.0124335.g001: Probit analysis of mortality due to phosphine exposure: S-strain x R-strain intercross.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 reciprocal F1 and F2 progeny are shown. A theoretical mortality response curve for the F2 is drawn based on the hypothesis that only a single gene contributes to the observed resistance.

Mentions: The probit curve of the S-strain indicated that it was genetically homogeneous with respect to its response to phosphine (P = 0.121) (Table 1). This genetic uniformity was clearly reflected in the log dose-probit mortality (ld-pm) line, which showed that observed plots of the S-strain matched the probit model exactly (Fig 1). In contrast, the strongly resistant (R-strain) and the reciprocal F1 progeny exhibited heterogeneity (P < 0.001 and hf = 8.55, 16.49, 21.89 for the R-strain, F1SR, F1RS, respectively) (Table 1). The level of resistance of the R-strain was calculated at the LC50 to be 52× that of the reference S-strain, and 2× for both reciprocal F1 progenies. The degree of dominance of F1(♀S-strain x ♂R-strain) and F1(♀R-strain x ♂S-strain) were -0.71 and -0.66, respectively (Table 1), indicating that the strong resistance trait was incompletely recessive. The ld-pm lines of the reciprocal F1 populations were essentially collinear (Fig 1) and the relative potency of F1(♀S-strain x ♂R-strain) and F1(♀R-strain x ♂S-strain) was 1.04 (0.866–1.250, 95% CL), providing reliable confirmation that the response to phosphine of each of the reciprocal F1 populations were indistinguishable. This proved the absence of maternal effects, indicating that strong resistance in S. oryzae is autosomal, and that the data from the reciprocal F1s could be pooled in later analyses.


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 intercross.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 reciprocal F1 and F2 progeny are shown. A theoretical mortality response curve for the F2 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.g001: Probit analysis of mortality due to phosphine exposure: S-strain x R-strain intercross.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 reciprocal F1 and F2 progeny are shown. A theoretical mortality response curve for the F2 is drawn based on the hypothesis that only a single gene contributes to the observed resistance.
Mentions: The probit curve of the S-strain indicated that it was genetically homogeneous with respect to its response to phosphine (P = 0.121) (Table 1). This genetic uniformity was clearly reflected in the log dose-probit mortality (ld-pm) line, which showed that observed plots of the S-strain matched the probit model exactly (Fig 1). In contrast, the strongly resistant (R-strain) and the reciprocal F1 progeny exhibited heterogeneity (P < 0.001 and hf = 8.55, 16.49, 21.89 for the R-strain, F1SR, F1RS, respectively) (Table 1). The level of resistance of the R-strain was calculated at the LC50 to be 52× that of the reference S-strain, and 2× for both reciprocal F1 progenies. The degree of dominance of F1(♀S-strain x ♂R-strain) and F1(♀R-strain x ♂S-strain) were -0.71 and -0.66, respectively (Table 1), indicating that the strong resistance trait was incompletely recessive. The ld-pm lines of the reciprocal F1 populations were essentially collinear (Fig 1) and the relative potency of F1(♀S-strain x ♂R-strain) and F1(♀R-strain x ♂S-strain) was 1.04 (0.866–1.250, 95% CL), providing reliable confirmation that the response to phosphine of each of the reciprocal F1 populations were indistinguishable. This proved the absence of maternal effects, indicating that strong resistance in S. oryzae is autosomal, and that the data from the reciprocal F1s could be pooled in later analyses.

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