Resistance to Diamide Insecticides in Plutella xylostella (Lepidoptera: Plutellidae): Comparison Between Lab-Selected Strains and Field-Collected Populations

Abstract

Diamondback moth, Plutella xylostella (L.; Lepidoptera: Plutellidae), is an important pest of crucifers worldwide. The extensive use of diamide insecticides has led to P. xylostella resistance and this presents a serious threat to vegetable production. We selected chlorantraniliprole (Rf) and flubendiamide (Rh) resistance strains of P. xylostella with resistance ratios of 684.54-fold and 677.25-fold, respectively. The Rf and Rh strains underwent 46 and 36 generations of lab-selection for resistance, respectively. Low cross resistance of Rh to cyantraniliprole was found. Cross resistance to chlorfenapyr, tebufenozid, and indoxacarb was not found in Rf and Rh strains. The P. xylostella ryanodine receptor gene (PxRyR) transcripts level in the Rf and Rh strains was up-regulated. Except for Rf34 and Rh36, PxRyR expression in all generations of Rf and Rh selection gradually increased with increasing resistance. Two resistant populations were field-collected from Guangzhou Baiyun (Rb) and Zengcheng (Rz) and propagated for several generations without exposure to any pesticide had higher PxRyR expression than the susceptible strain (S). In the S strain, PxRyR expression was not related to the resistance ratio. Gene sequencing found that the RyR 4946 gene site was glycine (G) in the S, Rf, and Rh strains, and was glutamate (E) with 70% and 80% frequency in the Rb and Rz populations, respectively. The 4946 gene site was substituted by valine (V) with the frequency of 30% and 20% in Rb and Rz populations, respectively. These results increase the understanding of the mechanisms of diamide insecticide resistance in P. xylostella.

Increased Responses of Phenoloxidase in Chlorantraniliprole Resistance of Plutella xylostella (Lepidoptera: Plutellidae)

“… a Part of data taken from our previous studies of Qin et al 2018 . b RR(Resistance Ratio) = LD 50 of resistant strain/LD 50 of susceptible strain.…”

“…The treated larvae named QR c57 , QR c58 , QR c59 , and QR c60 , respectively. And the toxicity of chlorantraniliprole in every generation of QR c and R c strains with 20 larvae was assayed by the topical application according to the previous studies, respectively ( Qin et al 2018 ). The test was replicated three times.…”

“…In addition, other mutations (resulted in E1338D, Q4594L, and I4790M [I4790K]) may coordinate mutations in RyR ( Guo et al 2014 , Jourakua et al 2020 ). Besides, the mRNA expression changes of PxRyR and cytochrome P450 CYP6BG1 ( Yan et al 2014 , Qin et al 2018 , Li et al 2018 ) are also important resistant mechanisms of P. xylostella to chlorantraniliprole.…”

Combined transcriptomic and proteomic analysis of flubendiamide resistance in Plutella xylostella

“…Results showed there to be a glycine (G) to glutamic acid (E) mutation (Troczka et al 2012; Troczka et al 2015) at target site 4,946 in highly diamide‐resistant populations of P. xylostella in Thailand and the Philippines, which is located near a transmembrane region of the carboxyl end of receptor gene, highly conserved in all insect ryanodine receptor (RyR) (Gong et al 2014), and is considered the main cause of the resistance of P. xylostella to chlorantraniliprole. In addition, the detoxification metabolism of enzymes, such as cytochrome P450 monooxygenase (P450), carboxylesterase (CarE), and glutathione S‐transferase (GST) (Hu et al 2014; Wang et al 2013), or the amino acid G4946E, E1338D, Q4594L, and I4790M (I4790K) coordinated mutations in RyR (Guo et al 2014; Jourakua et al 2020), or mRNA expression changes of PxRyR and cytochrome P450 CYP6BG1 (Li et al 2015; Li et al 2018; Qin et al 2018; Sun et al 2012; Yan et al 2014) are also important mechanisms by which P. xylostella resists chlorantraniliprole. We found that most of the aforementioned studies elucidate the mechanism of resistance to chlorantraniliprole, but few address the mechanism of resistance to flubendiamide.…”

Behavioral response and adaptive cost in resistant and susceptiblePlutella xylostellato Chlorantraniliprole

“…Diamides act selectively to activate the insect ryanodine receptor in the endoplasmic reticulum of insects, leading to irreversible muscle contraction, paralysis, and feeding cessations (Nauen, 2006). However, within a short period of time, DBM populations showed resistance, especially to chlorantraniliprole, in many countries including Brazil, China, Korea, USA, Philippines, India, Japan, Vietnam, and Thailand (Troczka et al ., 2012; Wang & Wu, 2012; Ribeiro et al ., 2014; Steinbach et al ., 2015; Nauen & Steinbach, 2016; Qin et al ., 2018). Additionally, in 2012 there were 79 insecticide molecules to which DBM populations had shown resistance (Sun et al ., 2012), whereas this number reached 95 molecules in 2018 (IRAC, 2018) and for this reason DBM is considered the most difficult cruciferous pest to control.…”