Submitted to: Annals of the Entomological Society of America
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/6/2014
Publication Date: 5/30/2014
Citation: Pearson, C.C., Backus, E.A., Shugart, H.J., Munyaneza, J.E. 2014. Characterization and correlation of EPG waveforms of Bactericera cockerelli (Hemiptera: Triozidae): variability in waveform appearance in relation to applied signal. Annals of the Entomological Society of America. 107(3):650-666. Interpretive Summary: The potato psyllid is the insect vector of the bacterium that causes zebra chip, an economically important disease of potato in the United States. Researchers at USDA-ARS Wapato in Washington and Parlier in California, in collaboration with scientists at the University of Florida, determined the feeding behavior of this insect and mechanisms by which it transmits the bacterium to potato plants. Six characteristic feeding behavioral activities were discovered, one of which referred to as “waveform family E” was identified as the activity during which acquisition and transmission of the bacterium occur. Better understanding of the psyllid feeding behavior and disease transmission will lead to faster identification and development of zebra chip resistant potato varieties and to maximize the efficiency of insecticides used to control this insect pest.
Technical Abstract: The potato psyllid, Bactericera cockerelli, was recently shown to be a vector of “Candidatus Liberibacter solanacearum” (Lso), a phloem-limited bacterium that is the putative causal agent of “Zebra Chip” in potato and unnamed diseases in other solanaceous species. Despite its importance, very little is known about B. cockerelli stylet probing behaviors that control transmission of Lso to its host plants. Herein, we report the first study identifying (characterizing) the electrical penetration graph (EPG) waveforms representing stylet penetration behaviors of the potato psyllid feeding on potato. Waveforms produced by adult B. cockerrelli on potato were also defined (correlated) using light microscopy of salivary sheath termini in plant tissue after probes were artificially terminated during the identified waveforms. In addition, behavioral activities were inferred based on similarities in waveform appearances with those of other psyllids, aphids and whiteflies, as well as electrical origins of waveforms. Adult B. cockerelli produced six waveform families, and four types, which represent the following proposed biological meanings: family A, initial penetration and saliva secretion, family B, penetration of epidermal cells, family C, secretion of most of the salivary sheath and stylet pathway in mesophyll/parenchyma, with two types, C1 and C2 of unknown meaning, family D, initial contact with phloem cells, family E, activities in phloem cells, with two types, E1, putative phloem salivation, and E2, phloem sap ingestion, as well as family G, xylem ingestion. In addition, a previously unreported variant of waveform G was characterized and correlated with applied signal type. Variation in waveform appearances was correlated with type and polarity of applied signal. Active phloem sap ingestion during E2 may play a critical role in acquisition of Lso bacterial cells. E1 probably plays a role in inoculation of the bacterium into phloem sieve elements, because it may represent salivation into phloem sieve elements. EPG waveforms of B. cockerelli could lead to faster development of resistant host plant varieties, strengthen integrated pest management strategies by incorporating alternative plant hosts, and maximize the efficiency of pesticides.