Grape Cultivar and Sap Culture Conditions Affect the Development of Xylella fastidiosa Phenotypes Associated with Pierce's Disease.

Lingyun Hao,Thomas J Burr,Paulo A Zaini,Harvey C Hoch,Patricia Mowery

doi:10.1371/journal.pone.0160978

Abstract

Xylella fastidiosa is a xylem-limited bacterium in plant hosts and causes Pierce’s disease (PD) of grapevines, which differ in susceptibility according to the Vitis species (spp.). In this work we compared X. fastidiosa biofilm formation and population dynamics when cultured in xylem saps from PD-susceptible and -resistant Vitis spp. under different conditions. Behaviors in a closed-culture system were compared to those in different sap-renewal cultures that would more closely mimic the physicochemical environment encountered in planta. Significant differences in biofilm formation and growth in saps from PD-susceptible and -resistant spp. were only observed using sap renewal culture. Compared to saps from susceptible V. vinifera, those from PD-resistant V. aestivalis supported lower titers of X. fastidiosa and less biofilm and V. champinii suppressed both growth and biofilm formation, behaviors which are correlated with disease susceptibility. Furthermore, in microfluidic chambers X. fastidiosa formed thick mature biofilm with three-dimensional (3-D) structures, such as pillars and mounds, in saps from all susceptible spp. In contrast, only small aggregates of various shapes were formed in saps from four out of five of the resistant spp.; sap from the resistant spp. V. mustangensis was an exception in that it also supported thick lawns of biofilm but not the above described 3-D structures typically seen in a mature biofilm from the susceptible saps. Our findings provide not only critical technical information for future bioassays, but also suggest further understanding of PD susceptibility.

Highlights

Xylella fastidiosa is a xylem-limited, Gram-negative bacterium that causes devastating diseases such as Pierce’s disease (PD) in grapevines, citrus variegated chlorosis in sweet oranges, and numerous other diseases in economically important plants, including the recently identifiedPLOS ONE | DOI:10.1371/journal.pone.0160978 August 10, 2016Grape Species and Culturing on Xylella fastidiosa Disease Associated Behaviors [https://nifa.usda.gov/program/capacity-grants]
We found that saps from PD-resistant V. champinii and V. aestivalis supported less X. fastidiosa biofilm development than those from V. vinifera, which correlated to growth differences in those saps
To exclude the possibly that nutrient depletion might have an effect in the observed phenotypes, we chose saps from V. vinifera, V. aestivalis, and V. champinii as the representatives of PD-susceptible and resistant spp., respectively, and examined biofilm formation when saps were renewed every two days in glass tubes

Summary

Introduction

Xylella fastidiosa is a xylem-limited, Gram-negative bacterium that causes devastating diseases such as Pierce’s disease (PD) in grapevines, citrus variegated chlorosis in sweet oranges, and numerous other diseases in economically important plants, including the recently identifiedPLOS ONE | DOI:10.1371/journal.pone.0160978 August 10, 2016Grape Species and Culturing on Xylella fastidiosa Disease Associated Behaviors [https://nifa.usda.gov/program/capacity-grants]. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

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