| Title: | An Indirect Defence Trait Mediated through Egg-Induced Maize Volatiles from Neighbouring Plants |
| Author(s): | Mutyambai DM; Bruce TJ; van den Berg J; Midega CA; Pickett JA; Khan ZR; |
| Address: | "Habitat Management Programme, International Centre of Insect Physiology and Ecology, P.O Box 30-40305, Mbita, Kenya. Biology Department, South Eastern Kenya University, P.O. Box 170-90200, Kitui, Kenya. Department of Biological Chemistry, Rothamsted Research, Harpenden, Herts, AL5 2JQ, United Kingdom. School of Biological Sciences, North-West University, Potchefstroom, 2520, South Africa" |
| DOI: | 10.1371/journal.pone.0158744 |
| ISSN/ISBN: | 1932-6203 (Electronic) 1932-6203 (Linking) |
| Abstract: | "Attack of plants by herbivorous arthropods may result in considerable changes to the plant's chemical phenotype with respect to emission of herbivore-induced plant volatiles (HIPVs). These HIPVs have been shown to act as repellents to the attacking insects as well as attractants for the insects antagonistic to these herbivores. Plants can also respond to HIPV signals from other plants that warn them of impending attack. Recent investigations have shown that certain maize varieties are able to emit volatiles following stemborer egg deposition. These volatiles attract the herbivore's parasitoids and directly deter further oviposition. However, it was not known whether these oviposition-induced maize (Zea mays, L.) volatiles can mediate chemical phenotypic changes in neighbouring unattacked maize plants. Therefore, this study sought to investigate the effect of oviposition-induced maize volatiles on intact neighbouring maize plants in 'Nyamula', a landrace known to respond to oviposition, and a standard commercial hybrid, HB515, that did not. Headspace volatile samples were collected from maize plants exposed to Chilo partellus (Swinhoe) (Lepidoptera: Crambidae) egg deposition and unoviposited neighbouring plants as well as from control plants kept away from the volatile emitting ones. Behavioural bioassays were carried out in a four-arm olfactometer using egg (Trichogramma bournieri Pintureau & Babault (Hymenoptera: Trichogrammatidae)) and larval (Cotesia sesamiae Cameron (Hymenoptera: Braconidae)) parasitoids. Coupled Gas Chromatography-Mass Spectrometry (GC-MS) was used for volatile analysis. For the 'Nyamula' landrace, GC-MS analysis revealed HIPV production not only in the oviposited plants but also in neighbouring plants not exposed to insect eggs. Higher amounts of EAG-active biogenic volatiles such as (E)-4,8-dimethyl-1,3,7-nonatriene were emitted from these plants compared to control plants. Subsequent behavioural assays with female T. bournieri and C. sesamiae parasitic wasps indicated that these parasitoids preferred volatiles from oviposited and neighbouring landrace plants compared to those from the control plants. This effect was absent in the standard commercial hybrid we tested. There was no HIPV induction and no difference in parasitoid attraction in neighbouring and control hybrid maize plants. These results show plant-plant signalling: 'Nyamula' maize plants emitting oviposition-induced volatiles attractive to the herbivore's natural enemies can induce this indirect defence trait in conspecific neighbouring undamaged maize plants. Maize plants growing in a field may thus benefit from this indirect defence through airborne signalling which may enhance the fitness of the volatile-emitting plant by increasing predation pressure on herbivores" |
| Keywords: | Animals Gas Chromatography-Mass Spectrometry Oviposition/physiology Plant Oils/chemistry Volatile Organic Compounds/*chemistry Wasps/*pathogenicity Zea mays/*chemistry/*parasitology; |
| Notes: | "MedlineMutyambai, Daniel M Bruce, Toby J A van den Berg, Johnnie Midega, Charles A O Pickett, John A Khan, Zeyaur R eng 2016/07/09 PLoS One. 2016 Jul 8; 11(7):e0158744. doi: 10.1371/journal.pone.0158744. eCollection 2016" |
