Resistance of novel insecticides in diamondback moth (Plutella xylostella) in Taiwan
Date Issued
2015
Date
2015
Author(s)
Chang, Chia-Che
Abstract
The diamondback moth (Plutella xylostella) belongs to the Lepidoptera order and is considered to be one of the most destructive pests of cruciferous vegetables, causing significant decreases in crop yields and increases in costs of pest control and management. It is estimated that management costs can reach up to 40 to 50 billion a year. In Taiwan, the control of diamondback moths mostly relies on the 44 insecticides registered for use. However, many current studies have reported differing diamondback moth resistance mechanisms to various pesticides, posing a challenge to diamondback moth control. This study explores the susceptibility of diamondback moths in Taiwan to 10 applied insecticides and also investigates the causes of resistance to new insecticides. Starting from late 2013 until early 2014, we tested the diagnostic doses of 11 applied insecticides in nine distinct regions. Spinetoram showed the highest mortality rates (80~100%). Regional differences were found in diamondback moth insecticide responses; the diamondback moths in Tainan Xinshi, Yunlin Xiluo, Chiayi Taibao, Yilan Datong, and Changhua Xihu showed higher levels of insecticide resistance. Field surveys in Changhua Xihu showed significantly decreasing mortality rates to the 10 types of applied insecticides over the past two years. Further pyrosequencing analysis located five resistance target genes and identified their mutation frequencies to related insecticides. In Taiwan, diamondback moths have developed resistance to pyrethroids, organophosphates, fipronil, and diamides. This study used high-throughput next generation sequencing to obtain 14G transcriptomes of the susceptible strain, resulting in 67,003 contigs by de novo assembly with average lengths of 822 bp; 172 CYPs, 38 GSTs, and 153 COEs of contigs were identified. In addition, 478 contigs were identified and grouped into 14 categories of insecticide target genes. In the emamectin benzoate-resistant strain, 10 CYPs, 4 GSTs, and 1 COE were identified, with ≧ 2 fold difference as compared to susceptible and field strains. In the tolfenpyrad-resistant strain, 4 GSTs, and 6 COE were identified, with ≧ 2 fold difference as compared to susceptible and field strains. In the chlorantraniliprole-resistant strain, 5 CYPs, 3 GSTs, and 1 COE were identified, with ≧ 2 fold difference ascompared to susceptible and field strains. In the flubendiamide-resistant strain, 6 CYPs, 4 GSTs, and 5 COE were identified, with ≧ 2 fold difference as compared to susceptible and field strains. All of these metabolic enzyme genes could be involved in insecticide resistance. In the emamectin benzoate-resistant strain, 2 amino acid substitutions were found on PxGABARα1; in the tolfenpyrad-resistant strain, a total of 18 amino acid substitutions were found on NADH dehydrogenases; in the chlorantraniliprole- and flubendiamide-resistant strains, 3 amino acid substitutions were found on RyR1. The results of this study could be used for future diamondback moth control, and the contig information could also prove useful for future development of insecticides, resistance management, and academic research.
Subjects
Plutella xylostella
chlorantraniliprole
flubendiamide
tolfenpyrad
emamectin benzoate
resistance
next generation sequencing
Type
thesis
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