Wild and cultivated tomatoes differ in their inter-individual variation in VOCs emissions after attack by Bactericera cockerelli (Sulc.) (Hemiptera: Psyllidae)

Abstract

Domestication reduces genetic population variation and changes resource allocation from defense to growth. As an indirect effect of plant domestication, the intraspecific variability of herbivore-induced plant volatiles (HIPV) has changed, modifying the odor of cultivated individuals compared to their wild relatives. Inter-individual variation in HIPV may constrain the use of chemical information for host location for insect herbivores or prey for insect predators. As HIPV are frequently considered a non-expensive indirect defense, domestication would probably not affect the correlation between constitutive and induced volatile emission. We tested the hypothesis that plant status, either cultivated or wild, determines the inter-individual variation of HIPV and the correlation between the constitutive and induced emissions amount. We used a before and after experimental approach to control for variation among individuals in constitutive emissions. We analyzed the variability of the induced response (the fold-change in concentration) and the variability in the volatile organic compounds (VOCs) constitutive and the induced emissions (before and after damage emission) of wild and cultivated tomato accessions (Solanum lycopersicum L.) attacked by nymphs of a tomato pest, the psyllid Bactericera cockerelli (Sulc.) (Hemiptera); we examined the variability of VOCs emission (odor intensity) and odor aroma (the VOCs blend's composition). The volatile constitutive emissions of cultivated accessions were more diverse and had higher inter-individual variation than wild accessions, while the induced emission variation was the same for wild and cultivated plants. We hypothesized that such variability is not a quality signal for herbivores and their natural enemies. The possible causes and ecological consequences of variation of volatile emission due to wild or cultivated status are discussed.