Resistance Monitoring And Detecting Beta-cypermethrin Resista In Shandong Spodoptera Exigua By Competitive PCR Ampliflcat Of Speciifc Allele (cPASA)

The beet armyworm (Spodoptera exigua Hubner) was a worldwide distributed andpolyphagous pest, which endangers various agricultural crops, such as vegetables, cotton et alin Shandong in recent years. At present chemical control plays an important in Spodopteraexigua control. The present studies were carried out to evaluate resisitance in Shandong Taian、Zhangqiu、Anqiu、Tengzhou and Binzhou populations of S. exigua to eleven insecticidesusing a standard leaf dip bioassay method. And we found that the conventional bioassay testsworkload shortcomings, so we established the DNA-based genotyping technique PASA forrapid detection of the L1014F mutation. This mutation, leucine to phenylalanine at position1014(L1014F)in sodium channel from the susceptible population (SS-WH) and the resistancepopulation (RR-Pyrethroid) of Spodoptera exigua (Hübner).The cPASA technique was usedto detect L1014F allele frequency, and through regression analysis and correlation analysis tothe filed mutions frequency and traditional leaf dip bioassay method, establishing an allelefrequency-LC50model. The results were summarized as follows:1Resistance monitoring in Spodoptera exigua.Spodoptera exigua (Hübner) collected from five regions from Shandong China wereevaluated for their susceptibilities to eleven insecticides (chlorantraniliprole, flubendiamide,emamectin benzoate, chlorfenapyr, indoxacarb, spinosyn, tebufenozide, methoxyfenozide,chlorfluazuron, beta-cypermethrin, and chlorpyrifos) in2011and2012using a leaf-dipbioassay method. The results indicate that field populations of S. exigua exhibit differentresistance levels to different insecticide. In recent year chlorantraniliprole and flubendiamidewas used extensively to control S. exigua because of its high-effecetive, LC50value<10.00mg/L. There was no resistance found in An qiu populations, however the resistancelevel of four other regions was very low to moderate, and the resistance of Binzhoupopulations was highest in2012, the resistance ratios was28.77. Similar to chlorantraniliprole,flubendiamide have the same resistance level. Compared with2011, the resistance of S exiguato these two insecticides seemed to be growing. The flied populations of S. exigua showedvery low to moderate resistance to emamectin benzoate, however emamectin benzoate stillhad the highest sensitivity, LC50value <1.00mg/L. In two years the resistance ratios ofchlorfenapyr was lower2-fold, it meaned that there was no chlorfenapyr resistance to S.exigua. Different populations of S. exigua showed low to high resistance to spinosyn andindoxacarb, in which the resistance to indoxacarb ranging from9.24-63.22-fold in2011to8.64-84.19-fold in2012, and the resistance ratio increased obviously from29.76to49.03in Luoyang regions; For the spinosyn, the resistance ratio were9.23-75.59-fold in2011,15.03-86.31-fold in2012, and the resistance ratio increased obviously from38.99to68.14inLuoyang region.For insect growth regulator, in five regions tebufenozide, methoxyfenzide andchlorfluazuron showed high to very high resistance level in S. exigua, and the resistance tochlorfluazuron was the most prominent, the resistance ratio was greater than200. Sochlorfluazuron can not contorl the pest effective in field. In2011and2012, the resistance oftebufenozide ranged from52.03to125.87; For methoxyfenzide, the resistance ratio rangedfrom131.25to675. The resistance to beta-cypermethrin were54.88-183.77-fold in2011,62.23~146.82-fold in2012, in which the resistance to S. exigua in Taian, Anqiu, TengzhouZhangqiu showed a declining trend, this may be associated with a decrease in pyrethroiduse.The resistance of chlorpyrifos showed very high reistance level in five regions Shandong,the resistance ratio ranged from106.29to349.51. Although the resistance of chlorpyrifos wasnot highest in eleven resistance monitoring insecticides, the sensitivity to S. exigua was mostinsensitive, and LC50value exceeded1000mg/L.There are several reasons accounting for varying degrees of resistance, includingselection pressure and the migration of S. exigua, meanwhile cropping structur andcross-resistance maybe play an important role.2Detecting beta-cpyrethroid resistance in Shandong S. exigua by cPASAA mutation, leucine to phenylalanine at position1014(L1014F)in sodium channel fromthe susceptible population (SS-WH) and the resistance population (RR-Pyrethroid)of(Hübner).The DNA-based genotyping technique PASA for rapid detection of the L1014Fmutation was established. The results showed that, none L1014F mutation individuals wasfound in the susceptible population.92%individuals from the ZQ-field population hadL1014F mutation(64%homozygotes and28%heterozygotes).After five generations ofselection to bêta-cypermethrin,25individuals of the RR-Pyrethroid populations had nonewildy type. It indicated that L1014F mutation was tightly associated with pyrethroidresistance in S.exigua.The results obtained by detecting kdr allele of five field populationshowed that kdr allele frequency was positive significantly correlated with LC50value ofbeta-cypermethrin (Y=1.106X+0.079, R2=0.930, P=0.0080).