Stylet penetration activities linked to the acquisition and inoculation of C andidatus L iberibacter solanacearum by its vector tomato potato psyllid

The tomato potato psyllid ( TPP ), B actericera cockerelli ( S ulc) ( H emiptera: T riozidae), is the main vector of the bacterium C andidatus L iberibacter solanacearum ( L so), a major disease of solanaceous crops. Feeding of TPP is associated with L so transmission. However, very little is known about the stylet penetration activities linked to acquisition and inoculation of L so. The electrical penetration graph ( EPG )‐ DC system was used to monitor stylet penetration activities during acquisition and inoculation of L so by individual TPP on tomato [ S olanum lycopersicum L . ( S olanaceae)]. Female TPP from L so‐free and L so‐infected colonies were used in acquisition and inoculation tests, respectively. In the acquisition tests, TPP were tested for L so after EPG recording of their stylet penetration activities on L so‐infected tomato shoots. In the inoculation tests, samples from the tomato plants on which the stylet penetration of L so‐infected TPP had been recorded were tested for L so infection. The relationships between qPCR results and the EPG waveforms (C, G, D, E1, and E2) representing the main stylet penetration activities performed by individual insects in inoculation and acquisition tests were investigated. Results confirmed that a single adult TPP is capable of infecting a plant with L so. Our data suggest that acquisition of the bacteria occurs during phloem ingestion (E2), and inoculation is likely associated with salivation into the phloem sieve elements (E1). The durations of EPG parameters were not significantly different between L so‐infected and L so‐free TPP (later shown by qPCR ) in acquisition tests. In inoculation tests, the durations of E1 or E2 recorded from TPP on L so‐infected and L so‐free plants that were later shown by qPCR were not significantly different. However, C was shorter on L so‐infected plants than on L so‐free plants, where TPP performed phloem activities. The minimum plant access period required for L so transmission by a single TPP was estimated to be ca. 2 h, with an acquisition threshold of about 36 min.