Maize landraces recruit egg and larval parasitoids in response to egg deposition by a herbivore

Abstract

Natural enemies respond to herbivore-induced plant volatiles (HIPVs), but an often overlooked aspect is that there may be genotypic variation in these 'indirect' plant defence traits within plant species. We found that egg deposition by stemborer moths (Chilo partellus) on maize landrace varieties caused emission of HIPVs that attract parasitic wasps. Notably, however, the oviposition-induced release of parasitoid attractants was completely absent in commercial hybrid maize varieties. In the landraces, not only were egg parasitoids (Trichogramma bournieri) attracted but also larval parasitoids (Cotesia sesamiae). This implies a sophisticated defence strategy whereby parasitoids are recruited in anticipation of egg hatching. The effect was systemic and caused by an elicitor, which could be extracted from egg materials associated with attachment to leaves. Our findings suggest that indirect plant defence traits may have become lost during crop breeding and could be valuable in new resistance breeding for sustainable agriculture.

Identification of leaf volatiles from olive (Olea europaea) and their possible role in the ovipositional preferences of olive fly, Bactrocera oleae (Rossi) (Diptera: Tephritidae)

“…Volatiles participate in plant reproduction, in tritrophic interactions, in belowground defense systems and in the abiotic stress response of plants (Dudareva et al, 2006). Regarding defense mechanisms, plants release volatile compounds with deterrent and repellent purposes to keep herbivores and pests away or, when attacked, to attract specific pest predators, parasitoids and other natural enemies and alert neighboring plants (Tamiru et al, 2011;Unsicker et al, 2009;Wu and Baldwin, 2010). Such compounds are globally recognized as semiochemicals (Paré and Tummlinson, 1999).…”

Back to the Origin: In Situ Studies Are Needed to Understand Selection during Crop Diversification

“…Second, plant genotypes vary in their ability to form positive relationships with beneficial species (Table 1; Smith and Goodman, 1999;Chen and Welter, 2005;Tamiru et al, 2011). Determining the relative roles of plant genetic diversity, microbial associates, and plant gene × environment interactions in conferring resistance to biotic and abiotic stresses (Philippot et al, 2013) would help elucidate whether breeding, microbial inoculation strategies, or natural enemy introductions would better support crop production in the diverse environments where crops are grown.…”

Volatile Semiochemical Mediated Plant Defense in Cereals: A Novel Strategy for Crop Protection

“…However, the volatile profiles dramatically change, both in quantities and ratios, after feeding damage or egg deposition by herbivore [5,13]. The bouquets of volatile semiochemicals produced by plants in response to insect infestation provide parasitoids and predators with reliable cues to locate the attacking herbivores as they can differentially perceive the induced volatile signals in the presence of their hosts or prey [18].…”

“…The bouquets of volatile semiochemicals produced by plants in response to insect infestation provide parasitoids and predators with reliable cues to locate the attacking herbivores as they can differentially perceive the induced volatile signals in the presence of their hosts or prey [18]. For instance, the maize plant, Z. mays, has been shown to emit large quantities of different HIPVs, above and below ground, in response to insect feeding and egg deposition [6,13]. Moreover, the HIPVs were produced locally at the site of insect attack and systemically throughout the plant [13].…”

“…Moreover, there is an increasing interest for semiochemicals based pest management in recent years, due to ecological and environmental costs associated with use of broad-spectrum insecticides. Unlike chemical insecticides, volatile semiochemicals are difficult for insects to develop resistance against, and work by a non-toxic mode of action through modifying the behaviour of the pest or its natural enemies to the detriment of the crop pest [12,13]. Furthermore, they are non-persistent, species-specific, cost-effective, and environmentally safe [11].…”