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Title: The influence of learning on host plant preference in a significant phytopathogen vector, Diaphorina citri

Author
item STOCKTON, DARA - University Of Florida
item MARTINI, XAVIER - University Of Florida
item Patt, Joseph - Joe
item STELINSKI, LUKASZ - University Of Florida

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/4/2016
Publication Date: 3/1/2016
Citation: Stockton, D.G., Martini, X., Patt, J.M., Stelinski, L.L. 2016. The influence of learning on host plant preference in a significant phytopathogen vector, Diaphorina citri. PLoS One. doi: 10.1371/PO.2016-0149815.

Interpretive Summary: Asian citrus psyllid is a tiny insect that transmits Huanglongbing, aka citrus greening, a devastating disease that threatens citrus trees worldwide. This psyllid reproduces only on the young leaves of citrus and it close relatives, such as orange jasmine and curry leaf. The results of this study will improve our ability to detect, monitor and predict its movements. This will help growers know how many psyllids are in the vicintity of their groves. We examined whether psyllids could learn to recognize colors and aromas of its host plants. Although many plant-feeding insects are guided by instinct to find plants, their preference may be influenced by experience and is not dictated by instinct alone. The results of our study showed that: a) foraging experience by young psyllids on a particular plant species translated into preference for that plant species as an adult; b) adults psyllids could learn to associate novel aromas and neutral colors with a particular plant species; and, c) they retained their memory of certain aromas and colors, once they learned them, for at least 48 hrs.

Technical Abstract: Although specialist herbivorous insects are guided by innate responses to host plant cues, host plant preference may be influenced by experience and is not dictated by instinct alone. The effect of learning on host plant preference was examined in the Asian citrus psyllid, Diaphorina citri, vector of the causal agent of citrus greening disease or huanglongbing. We investigated a) whether foraging experience on a particular host plant species as an immature translated into preference for that host as an adult; b) whether adults psyllids could learn to associate novel olfactory and neutral visual stimuli with a particular host plant species; and, c) cognitive dynamics such as memory duration and recognition of compound stimuli. Learning was measured by cue selection in a 2-choice behavioral assay and compared to naïve controls. Our results showed that learned responses in D. citri are complex and diverse. Natal host plant type had a strong influence on olfactory host plant preference as an adult, with psyllids preferring the species on which they were reared. Memories for natal host plant cues were maintained for at least 48 hours, but were subject to change with the introduction of an alternative host plant. Additionally, learning occurred for multiple sensory modalities, where novel olfactory and visual environmental cues were associated with the host plant. Males displayed weaker discriminatory abilities in more complex learning tasks than did females. These findings suggest Diaphorina citri are dynamic organisms that can learn to recognize multiple types of sensory stimuli pertaining to their host plants. These experience-based associations are possibly used by adults to locate and select suitable host plants for feeding and reproduction.