Influence of Citrus Plants Infected withXylella fastidiosaon Stylet Penetration Activities ofBucephalogonia xanthophis(Hemiptera: Cicadellidae)

Abstract

Xylem colonization by Xylella fastidiosa promotes physiological, biochemical, and morphological alterations in citrus plants causing citrus variegated chlorosis (CVC) disease, which might infiuence the feeding behavior of vectors of this bacterial pathogen and its spread in citrus groves. By using the electrical penetration graph technique, we compared the numbers and durations of stylet penetration activities by adults ofthe sharpshooter vector Bucephalogonia xanthophis (Berg) (Hemiptera: Cicadellidae) on healthy and X. fastidiosa-infected sweet orange seedlings {Citrus sinensis (L. ) Osbeck, cv. Pera). Infected plants were either symptomatic, exhibiting the typical CVC, symptoms or totally asymptomatic. The mean time needed to contact xylem and start xylem sap ingestion after the onset ofthe first probe was similar among treatments. However, the average time elapsed between the onset ofthe first probe and the beginning of sustained xylem ingestion (>5 min) was longer on plants with CVC symptoms than on infected asymptomatic or healthy plants. In addition, the length of time spent in ingestion activities was much shorter on symptomatic plants. Our results showed that CVC symptomatic citrus plants were a less acceptable host than uninfected or asymptomatic X. /astidiosa-infected plants. Furthermore, our results support the hypothesis that symptomless infected citrus trees may be more important as sources for CVC spread than severely diseased ones.

Plant defense against a pathogen drives nonlinear transmission dynamics through both vector preference and acquisition

“…3A). Previous work also found that cicadellid vectors of X. fastidiosa-including our study species-consistently avoid symptomatic infected host plants (Marucci et al 2005, Daugherty et al 2011, De Miranda et al 2013. Furthermore, when avoidance was clear in our study, it was realized through differences in attraction rates, corroborating previous research that cicadellid vectors orient toward Fig.…”

“…The bacterium is transmitted in a propagative persistent but non‐circulative manner by xylem‐sap‐feeding insect vectors in the family Cicadellidae and superfamily Cercopoidea, with all xylem‐sap‐feeding Hemiptera regarded as potential vectors (Sicard et al 2018). Cicadellid vector species consistently avoid X. fastidiosa‐ infected symptomatic plant hosts but show no discrimination between infected asymptomatic hosts and uninfected hosts (Marucci et al 2005, Daugherty et al 2011, De Miranda et al 2013).…”

Feeding behavior in relation to spittlebug transmission of Xylella fastidiosa

“…Furthermore, the low acquisition rate could have been influenced by the relatively low bacterial population within our olive source plants, given the positive correlation between X. fastidiosa population within the infected plant and the transmission efficiency ( (Hill and Purcell 1997). Nevertheless, high X. fastidiosa population lead to symptoms development, and the vectors tend to discriminate against symptomatic plants (Marucci et al 2005;Miranda et al 2013;Zeilinger and Daugherty 2014;Del Cid et al 2018). Therefore, considering our scenario, consisting of infected but non-symptomatic plants bearing a bacterium population still too low to cause severe symptoms and consequent reduction of host plant attractiveness, the most epidemiologically realistic for inferences on acquisition dynamic.…”

How Do Plant Diseases Caused byXylella fastidiosaEmerge?

“…This behavior may be advantageous for these insects: water stressed and X. fastidiosa-infected plants have some shared physiological characteristics, of which xylem sap under high tension is of paramount relevance. Increased tension in a water column leads to a food source that is energetically expensive for insects, resulting in the ingestion of less xylem sap (Andersen et al 1992;Miranda et al 2013) and promoting the movement of vectors to another host (Krugner et al 2012). Since symptomatic plants are heavily colonized by X. fastidiosa (Newman et al 2003), avoidance of infected plants by vectors may act to reduce transmission rates when disease incidence is low (Sisterson 2008;Zeilinger and Daugherty 2014) and select for decreased bacterial virulence.…”