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The selection for and genetical analysis of phosmet resistance in Amblyseius nicholsi.
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1989
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Unknown Venue
BotanyAmblyseius NicholsiGeneticsEntomologyPlant PathologyApplied GeneticsGenetical AnalysisToxicologyPhosmet ResistanceInsecticidePublic HealthOp InsecticidesPlant ProtectionPest ManagementGenetic VariationIntegrated Plant ProtectionPopulation GeneticsBiologyPesticide ResistanceEvolutionary BiologyCrop ProtectionInduced ResistancePest ControlMicrobiologyEnvironmental ToxicologyCitrus GrovesHost ResistanceMedicine
The predacious mite Amblyseuts nicholsi is an important natural enemy of the citrus red mite Panoopychus citri. However, this predator is very susceptible to organophosphorus (OP) insecticides such as phosmet and dimethoate, whlch are commonly used in Guangdong Province to control the citrus psylla Diaphorina citri, a vector of citrus yellow shoot disease. It is neces-sary to raise the resistance of the predator to OP insecticides so that they can be used in the citrus groves in combination.Determination of phosmet resistance of this predator was conducted by the slide-dip method of the laboratory population collected from Guangzhou and selection was started in June, 1982, with phosmet in ascending concentrations starting with 60 ppm of active ingrdient. After 33 generations of selection a resistant strain (R) was obtained, with LC50 for phosmet rising to 995 ppm as compared with 52.5 ppm in the original susceptible population (S). Thus, a 18.9-fold increase in resistance for phosmet was obtained in June, 1984, and the LD-P lines of R and S were nearly parallel. The LD-P lines of 1i females of reoiprocal crosses (S♀×Rf4 and R♀× S♂) were intermediate between those of R and S, and sliglitly closer to the former. The degree of dominance of F1 female hybrids were 1.4 and 1.9, indicating that the phosmet resistance is determined by semidominant gene. In the female offspring from heterozygote females back-crossed with S males, the ratio of SS to SR is approximately 1:1 and a plateau appears a't the 50% mortality of the LD-P line? It is concluded that resistance to phosmet in this predator is controlled by a single semidominant allele. An examination of resistance of F1 male hybrids of reciproca) crosses (S♂ × R♀ and R♀ × S♂) revealed that F1 males inherited the resistant gene from their mothers, exemplifying the parahaploidy model in some species of Phytoseiidae. The high cross-resistance to phoxim and weak cross-resistance to optunal, dimethoate, vapona, and trichlorfor were found present in the phosmet resistant strain and the resistance levels for these five insecticides have been improved to 28.8, 8.5, 5.4, 3.8 and 2.7 fold respectively.