Trichoplusia ni (Lepidoptera: Noctuidae) survival, immune response, and gut bacteria changes after exposure to Azadirachta indica (Sapindales: Meliaceae) volatiles
Keywords:
biological insecticide, chemical insecticide resistance marker, enterobacteria, immune marker, neem VOCAbstract
Volatile organic compounds (VOCs) produced by the neem tree (Azadirachta indica A. Juss.; Sapindales: Meliaceae) are known to alter growth and development of several insects. Additionally, the insect’s gut microbiota and immune response are key components in insect development and have been linked to increased resistance to insecticides. In the present study, larval mortality, immune response, and intestinal bacteria changes in the cabbage ooper, Trichoplusia ni (Hübner) (Lepidoptera: Noctuidae), induced by VOCs of dried and milled neem leaves, stems, and bark were investigated. Exposure of neonates to 10 g of mixed dried leaves and stems resulted in 79 and 63% mortality of laboratory and field T. ni strains, respectively. In addition, differences were observed in larval weights and pupal sizes during 30 d of incubation. Further studies included transcript amplification of enterobacteria genes and genes related to immune responses and chemical synthetic insecticide resistance. Midguts from the VOC-exposed laboratory strain of T. ni larvae over-transcribed cytochrome P450 (CYP4L4), PGRP, lysozyme, attacin, cecropin, defensin, gallerimycin, and lebocin, compared with unexposed control larvae, whereas ribosomal protein S5 (internal control) and caspase transcripts did not show changes. These samples revealed reduced enterobacteria transcript amplification (27%), suggesting bacterial repression. The effect of neem VOCs on the immune response may in part explain the inhibitory effect on the molting process, in which chitin is broken down to release the old cuticle between instars. Because neem leaves, stems, and bark are widely used as fertilizers, their potential application in pest management programs for controlling T. ni on host crops (cauliflower, broccoli, or cabbage) is discussed.
Resumen
Se tienen reportes donde mencionan que los compuestos orgánicos volátiles (COVs) producidos por el árbol de neem (Azadirachta indica A. Juss.; Sapindales: Meliaceae) pueden alterar el crecimiento y desarrollo de algunos insectos. Además, la microbiota intestinal del insecto y la respuesta inmune son componentes clave en su desarrollo y se han relacionado con una mayor resistencia a algunos insecticidas. Al investigar la susceptibilidad y alteraciones fisiológicas de una plaga Lepidoptera, se observó la mortalidad de larvas de dos cepas del gusano falso medidor Trichoplusia ni (Hübner) (Lepidoptera: Noctuidae) después de su exposición a COVs de hojas, corteza y tallos (secos y molidos) del neem. Se observó una mortalidad del 79% y 63% de neonatas de las cepas NL (laboratorio) y Gto (campo), respectivamente, después de exponerlas a los COVs producidos por 10 gramos de hojas secas o tallos, además de diferencias en el peso de larvas y tamaño de pupas después de un periodo de incubación máximo de 30 días. Al analizar la amplificación de transcritos de genes de microbiota intestinal y genes de respuesta inmune relacionados con resistencia a insecticidas químicas, los resultados mostraron que el intestino de larvas de T. ni de la cepa NL expuestas a COVs sobre-traducían citocromo P450 (CYP4L4), PGRP, lisozima, atacina, cecropina, defensinas, galeromicina y lebocina al compararla frente a larvas no expuestas (control), mientras que no se observaron diferencias con la proteína ribosomal S5 (control interno) y la caspasa. Mismas muestras revelaron una amplificación reducida (27%) de transcritos para enterobacterias, lo que sugiere una represión bacteriana. El efecto de COV del neem en la respuesta inmune podría explicar en parte algún bloqueo en la muda larvaria o pupación. Debido a que hojas, tallos y corteza de neem se utilizan principalmente como fertilizante, se discute su uso potencial en programas de manejo de plagas para el control de T. ni en cultivos hospederos (coliflor, brócoli o repollo).
Downloads
Published
Issue
Section
License
Copyright for any article published in Florida Entomologist is held by the author(s) of the article. Florida Entomologist is an open access journal. Florida Entomologist follows terms of the Creative Commons, Attribution Non-Commercial License (cc by-nc). By submitting and publishing articles in Florida Entomologist, authors grant the FOJ and Florida Entomologist's host institutions permission to make the article available through Internet posting and electronic dissemination, and to otherwise archive the information contained both electronically and in a hard printed version. When used, information and images obtained from articles must be referenced and cited appropriately. Articles may be reproduced for personal, educational, or archival purposes, or any non-commercial use. Permission should be sought from the author(s) for multiple, non-commercial reproduction. Written permission from the author(s) is required for any commercial reproduction.