No abstract

Diamondback moth (DBM), Plutella xylostella, is an important pest of crucifers worldwide. The extensive use of diamide insecticides has led to DBM resistance in the world, and this presents a serious threat to vegetable production. In the present study, transcriptomic and proteomic analyses were combined to investigate the potential flubendiamide-resistance mechanism in DBM. The lab-selected (R h) and field-collected (R b) flubendiamide-resistant lines of P. xylostella with resistance ratios of 1889.92-fold and 1250.97-fold, respectively, were used, as well as a lab-reared flubendiamide-susceptible line (S). Compared with the S group, the transcriptomic analysis revealed 151 upregulated and 287 downregulated gene messengers in the R h group and 432 upregulated and 565 downregulated gene messengers in the R b group. The most frequently enriched pathways of differentially expressed genes (DEGs) were mainly involved in metabolic pathways. Metabolism related genes, including two P450, two ABC transporters, and three trypsins, were upregulated in the R h line. Additionally, some P450 genes, trypsin, juvenile hormone (JH), and mucin genes were also upregulated in the R b line. In proteomic analysis comparisons with the S group, there were 78 upregulated and 90 downregulated proteins in the R h group and 221 upregulated and 155 downregulated proteins in the R b group. Further analyses found that three CYP and 11 CYP proteins were over-expressed in R h and R b lines, respectively. Four glutathione S-transferase (GST) and four UGTs were over-expressed in R b line. So, we deduced that the detoxification metabolism may be the main mechanism of flubendiamide resistance in P. xylostella.

Abstract The diamondback moth (Plutella xylostella, DBM) is an important pest of cruciferous vegetables. The use of chlorantraniliprole has been essential in the management of the DBM. However, in many countries and areas, DBM has become highly resistant to chlorantraniliprole. Three different DBM strains, susceptible (S), chlorantraniliprole-selected (Rc), and field-collected (Rb) resistant strains/populations were studied for the role of phenoloxidase in resistance development to the insecticide. By assaying the activity of phenoloxidase (PO) in the three different DBM strains, the results showed that the PO activity in the Rc strain was increased significantly compared with the S strain. The synergistic effects of quercetin showed that the resistant ratio (RR) of the QRc larvae to chlorantraniliprole was decreased from 423.95 to 316.42-fold compared with the Rc larvae. Further studies demonstrated that the transcriptional and translational expression levels of PxPPO1 (P. xylostella prophenoloxidase-1 gene) and PxPPO2 (P. xylostella prophenoloxidase-2 gene) were increased to varying degrees compared with the S strain, such as the transcriptional expression levels of PxPPO2 were 24.02-fold that of the S strain. The responses of phenoloxidase were significantly different in chlorantraniliprole-resistant DBM.

The southern root-knot nematode (RKN), Meloidogyne incognita , causes significant damage to vegetable production and is a major problem in greenhouse tomatoes. The effect of a combination of fluopyram and abamectin, at a mass ratio of 1:5, was studied for RKN control. Pot trials showed that fluopyram, abamectin, and their combination at three dosages increased the height, stem diameter, root fresh weight, shoot fresh weight, and the root length of tomato plants. The RKN control efficacy of the 1:5 combination at 450 g a.i./ha was 74.06% at 30 days after transplanting (DAT), and the control efficacy of the combination at 337.5 and 450 g a.i./ha differed significantly from those of other treatments at 60 DAT. The root-galling index (RGI) control efficacy of the combination at 450 g a.i./ha and of fluopyram (41.7% SC) only at 450 g a.i./ha were better than the control efficacies of other treatments, and these two treatments significantly increased root activity. Field trial results showed that the soil nematode control efficacy was similar to that of the pot trials at 30 and 60 DAT. The RGI control efficacy of the combination at 337.5 and 450 g a.i./ha and of fluopyram (41.7% SC) only at 450 g a.i./ha differed significantly from those of the two other treatments. The tomato yields of the 1:5 combination at 450 g a.i./ha were increased by 24.07 and 23.22% compared to the control in field trials during two successive years. The combination of fluopyram and abamectin provides good nematode measure, and it can increase tomato yields. It provides an effective solution for the integrated management of southern RKN.