Signal Grass (Brachiaria brizantha) Oviposited by Stemborer (Chilo partellus) Emits Herbivore-Induced Plant Volatiles That Induce Neighbouring Local Maize (Zea mays) Varieties to Recruit Cereal Stemborer Larval Parasitoid Cotessia sesamiae
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Date
2015
Authors
Magara, H.J.O.
Midega, Charles A.O.
Otieno, Siprine Akinyi Ogol
Calistus, K.P.O.
Bruce, Toby J.A.
Pickett, John A.
Zeyaur, R. Khan
Journal Title
Journal ISSN
Volume Title
Publisher
Global Society of Scientific Research and Researchers
Abstract
Plants respond to attack by herbivores with the release of herbivore-induced plant volatiles (HIPVs).
In return, natural enemies (predators and parasitoids) respond to these emitted herbivore-induced plant volatiles while foraging for their hosts. Neighboring plants of the same family may be induced by the emitted HIPVs. This is a tritrophic interaction that leads to an ‘indirect’ plant defense characteristic within species that recruit the natural enemies to ward off pests. The objective of this study was to evaluate the effect of HIPVs of B. brizantha on neighbouring maize plants on the management of Chilo partellus. This was done by entrainment of volatiles from five maize varieties: Nyamula (local maize), jowi (local maize), Cuba 91 (a landrace from Cuba), Western hybrid 505 (WH505) and Pwani hybrid 4 (PH4). In the first set up we exposed the five maize varieties to B. brizantha with C. partellus eggs for 48 hours and removed them from the grass and then entrained them. In the second set up we exposed these five maize varieties to B. brizantha without C. partellus eggs for 48 hours and removed them from the grass and then entrained them. Lastly in the third set up we entrained non-exposed maize plants. Olfactory responses of the cereal stemborer parasitoid Cotesia sesamiae to volatiles emitted by these maize plant varieties were studied in a 4-way olfactometer. Gas chromatography and coupled Gas chromatography-Mass spectrometry was done to identify physiologically active compounds of the collected volatiles. The findings indicated that egg ovi position by the gravid Chilo partellus on signal grass Brachiaria brizantha caused production of HIPVs that further induced smallholder farmers’ own maize varieties (Nyamula and Jowi) and a landrace maize from Latin America (Cuba 91) to attract Cotessia sesamiae, a parasitoid of Chilo partellus. Gravid females of Cotessia sesamiae were significantly more attracted to the volatiles of the smallholder farmers’ own maize varieties and Latin America landrace maize exposed to B. brizantha with Chilo partellus eggs. In contrast, olfactometer bioassays showed that female C. sesamiae were significantly less attracted to HIPVs from plants exposed to B. brizantha without C. partellus eggs and to volatiles from non-exposed maize plants to either grass with eggs or without eggs. Hybrids were not induced hence had no significant result. This holds a promise for development of a sophisticated defense strategy whereby parasitoids are recruited in advance, awaiting the eggs to hatch. When the eggs hatch, the larvae are attacked, stopping them from damaging the maize crop. Our findings indicate that B. brizantha can be used to induce defense in a neighboring maize crop to attract C. sesamiae parasitoids and as a trap crop to ward off stemborers from the maize crop. This trait inB. brizantha should be tested further in other cereal crops to access their potential of being induced. The possible role of signal grass in pest management is discussed.
Description
Keywords
Brachiaria brizantha, Chilo partellus, Cotesia sesamiae, Herbivore induced plant volatiles, inducing defense, Insect oviposition, trap crop, Tritrophic interaction, Zea mays
Citation
International Journal of Sciences: Basic and Applied Research (IJSBAR) (2015) Volume 19, No 1, pp 341-357