Characterization of the electrical penetration graphs of the psyllid Bactericera trigonica on carrots

Abstract

The psyllid Bactericera trigonica Hodkinson (Hemiptera: Triozidae) is a carrot and celery pest recently described as a vector of the plant pathogenic bacterium Candidatus Liberibacter solanacearum (Lso) on Apiaceae. Detailed information on vector stylet penetration activities is essential in the study of Lso transmission. In this study we used the electrical penetration graph (EPG) technique, characterized waveforms produced during the various stylet penetration activities in carrot leaves, and correlated them with stylet tracks and salivary sheath termini on plant tissues as well as with Lso inoculation. In addition, the effect of Lso in B. trigonica on the stylet penetration activities was tested. The EPG waveforms identified were: waveforms C1 and C2 detected in the mesophyll, waveforms D, E1, and E2 near or in the phloem sieve elements, and waveform G in the xylem vessels. A waveform pattern not previously reported for psyllids was the ‘pseudo‐potential drop’ (pseudo‐pd), characterized by sudden voltage dips similar to potential drops. However, the lowered voltage appeared to be inverted when the plant voltage is negative, indicating that it is caused by an increased resistance period and not due to a cell puncture. A direct correlation is shown between the waveform E1 and salivation into phloem sieve elements by B. trigonica as the inoculation of Lso occurred in a period as short as 30 s of E1; Lso transmission occurred in 17 of 35 plants (48%). Stylet activities during waveforms C or D had no consequences on the inoculation of Lso. In conclusion, Lso infection directly affects the probing behaviour of B. trigonica by increasing the total duration of C and D waveforms, but not variables related to phloem salivation (Lso inoculation) or ingestion (Lso acquisition). The reported information here is fundamental for identifying the psyllid vector traits of behaviour associated with transmission of Lso to Apiaceae.

Transmission of ‘Candidatus Liberibacter solanacearum’ by Bactericera trigonica Hodkinson to vegetable hosts

“…In our work, EPG waveforms were analogous to those described for other psyllids (Bonani et al, 2010;Civolani et al, 2011;Pearson et al, 2014;Mustafa et al, 2015) and those described for B. trigonica by Antolínez et al (2017c). Acquisition of the bacteria is associated with the phloem ingestion (E2 waveform), whereas inoculation is associated with salivation into the phloem sieve elements (E1 waveform) (Sandanayaka et al, 2014;Antolínez et al, 2017c).…”

“…Short periods of E1 activity in the phloem of potato plants indicate the possibility of transmission, although at a low efficacy, since the success of the inoculation is directly correlated with the duration of this period of salivation. However, we must consider that the insect can inoculate the bacterium in a period as short as 30 seconds in a preferred host such as carrot (Antolínez et al, 2017c), and that these studies only covers a limited period of 8 h.…”

“…The EPG waveforms previously described for psyllids (Bonani et al, 2010;Civolani et al 2011;Antolínez et al, 2017c) were identified as follow: nonprobing (np), intercellular apoplastic stylet pathway (C waveform), initial contact with phloem tissue (D waveform), salivation into phloem sieve elements (E1 waveform), passive phloem sap uptake from the phloem sieve elements (E2 waveform) and active intake of xylem sap from xylem elements (G waveform). The behavioural variables were processed using the MS (1 g/L of Confidor®, Bayer CropScience) outside the room after each transmission experiment to eliminate any nymphs emerging from the eggs and were grown in a greenhouse for one month, and then new leaves were tested by real-time PCR to confirm CaLso infection.…”

Newly Distinguished Cell Punctures Associated with Transmission of the Semipersistent Phloem-Limited Beet Yellows Virus

“…The electrical penetration graph (EPG) technique has been largely used to identify specific stylet penetration (probing) activities in aphids related to virus transmission (16,17,50) as well as to other insect-transmitted plant pathogens such as bacteria transmitted by psyllids (18,19). Monitoring aphid feeding behavior by EPGs enables us to learn of the stylet tip positions in the different plant tissues and the specific stylet activities by observing several waveforms described for aphids (20,21).…”

Psilídeos (Hemiptera: Psylloidea) associados a olerícolas e estudo das interações com suas plantas hospedeiras

“…No caso de pimentão, a pouca preferência do inseto pela planta, resultou em poucas tentativas de chegar ao floema e de se alimentar, muito menos que as plantas de cenoura e tomate. É importante ressaltar que em teste com Bactericera trigonica em cenoura, apenas 30 s de onda E1 já resultou em inoculação de CaLsol (Antolinez et al, 2017b). Este tempo mínimo foi realizado por R. solanicola em todas as plantas testadas neste trabalho.…”