title: Insecticidal potency of RNAi-based catalase knockdown in Rhynchophorus ferrugineus (Oliver) (Coleoptera: Curculionidae).
abstract: BACKGROUND
  Palm trees around the world are prone to notorious Rhynchophorus ferrugineus, which causes heavy losses of palm plantations. In Middle Eastern countries, this pest is a major threat to date palm orchards. Conventional pest control measures with the major share of synthetic insecticides have resulted in insect resistance and environmental issues. Therefore, in order to explore better alternatives, the RNAi approach was employed to knock down the catalase gene in fifth and tenth larval instars with different dsRNA application methods, and their insecticidal potency was studied.
  
  
  RESULTS
  dsRNA of 444 bp was prepared to knock down catalase in R. ferrugineus. Out of the three dsRNA application methods, dsRNA injection into larvae was the most effective, followed by dsRNA application by artificial feeding. Both methods resulted in significant catalase knockdown in various tissues, especially the midgut. As a result, the highest growth inhibition of 123.49 and 103.47% and larval mortality of 80 and 40% were observed in fifth-instar larvae, whereas larval growth inhibition remained at 86.83 and 69.08% with larval mortality at 30 and 10% in tenth-instar larvae after dsRNA injection and artificial diet treatment. The topical application method was the least efficient, with the lowest larval growth inhibition of 57.23 and 45.61% and 0% mortality in fifth- and tenth-instar larvae. Generally, better results were noted at the high dsRNA dose of 5 µL.
  
  
  CONCLUSIONS
  Catalase enzyme is found in most insect body tissues, and thus its dsRNA can cause broad-scale gene knockdown within the insect body, depending upon the application method. Significant larval mortality and growth inhibition after catalase knockdown in R. ferrugineus confirms its insecticidal potency and suggests a bright future for RNAi-based bioinsecticides in pest control. © 2016 Society of Chemical Industry.
authors.affiliation: Life Science and Environment Research Institute, King Abdulaziz City for Science and Technology, Riyadh, Saudi Arabia.
authors.forename: Hassan
authors.initials: H
authors.lastname: Al-Ayedh
authors.affiliation: Department of Arid Land Agriculture, College of Agriculture and Food Science, King Faisal University, Hofuf, Saudi Arabia.
authors.forename: Muhammad
authors.initials: M
authors.lastname: Rizwan-Ul-Haq
authors.affiliation: Department of Arid Land Agriculture, College of Agriculture and Food Science, King Faisal University, Hofuf, Saudi Arabia.
authors.forename: Abid
authors.initials: A
authors.lastname: Hussain
authors.affiliation: Department of Arid Land Agriculture, College of Agriculture and Food Science, King Faisal University, Hofuf, Saudi Arabia. aljabr@kfu.edu.sa.
authors.forename: Ahmed M
authors.initials: AM
authors.lastname: Aljabr
mesh_terms: D000287:Administration, Topical; D000821:Animal Feed / Q000032:analysis; D000818:Animals; D002374:Catalase / Q000235:genetics* / Q000378:metabolism; D055785:Gene Knockdown Techniques; D020868:Gene Silencing; D007300:Insect Control / Q000379:methods*; D019476:Insect Proteins / Q000235:genetics* / Q000378:metabolism; D007306:Insecticides; D007814:Larva / Q000254:growth & development; D008845:Microinjections; D034622:RNA Interference; D048889:Weevils / Q000254:growth & development
chemical_list: D019476:Insect Proteins; D007306:Insecticides; D002374:Catalase
keywords: RNAi/dsRNA; Rhynchophorus ferrugineus; bioinsecticide; catalase; growth inhibition and mortality