Temperature-Dependent Growth and Survival of Xylella fastidiosa in Vitro and in Potted Grapevines

Abstract

Xylella fastidiosa is a xylem-inhabiting bacterium that causes Pierce's disease (PD) of grapevine. Growth rates of X. fastidiosa in a rich liquid medium were determined by culturing methods at various temperatures. The slope of the regression line between the points of 18 and 28°C was similar to that reported for Escherichia coli between 12 and 30°C and for Erwinia amylovora between 9 and 18°C. For three PD strains, two almond strains, and an oleander strain, X. fastidiosa grew fastest at 28°C but did not grow at 12°C. Grape seedlings kept at 5, 10, 17, or 25°C for 18 days, beginning 2 weeks postinoculation at 25°C, had 230-fold lower populations of X. fastidiosa when kept at 5°C, but populations did not change significantly over time at the other temperatures. In planta populations of X. fastidiosa decreased 3 days after placing the seedlings at 5 and 37°C, and subsequent samples yielded no culturable bacteria at 37°C. Based on in vitro and in planta studies, it appears that temperatures between 25 and 32°C may be critical for the epidemiology of Pierce's disease because of its rapid growth rate at these temperatures, whereas temperatures below 12 to 17°C and above 34°C may affect the survival of X. fastidiosa in plants.

Scientific Opinion on the risks to plant health posed byXylella fastidiosain the EU territory, with the identification and evaluation of risk reduction options

“…Although the recovery mechanism remains unknown, low winter temperatures increase the rate of recovery . In the field, recovery happens more often when infections occur in the summer or autumn than during the spring (Feil and Purcell, 2001). It should be noted that winter recovery has been demonstrated for grapevines infected with X. fastidiosa subsp.…”

“…However, X. fastidiosa can survive in dormant grapevine plant material in the vineyard, and if grape plant material is cut and stored over the winter at 4°C, after rooting, it can still be infected (Feil, 2001). …”

“…Several approaches have been used to infer the suitability of climatic zones for X. fastidiosa, mostly in the USA and based on the subspecies fastidiosa. Purcell and Feil (2001) proposed using isotherms of January winter temperature for zones where Pierce's disease has a severe (4.5 °C), occasional (1.7 °C) or rare (-1.1 °C) impact on grapes. Hoddle (2004) used CLIMEX to produce maps of potential distribution for X. fastidiosa and H. vitripennis, based on data from Feil and Purcell (2001) and Feil (2001).…”

“…Purcell and Feil (2001) proposed using isotherms of January winter temperature for zones where Pierce's disease has a severe (4.5 °C), occasional (1.7 °C) or rare (-1.1 °C) impact on grapes. Hoddle (2004) used CLIMEX to produce maps of potential distribution for X. fastidiosa and H. vitripennis, based on data from Feil and Purcell (2001) and Feil (2001). The optimum in vitro growth temperature for the bacteria is 28 °C, and no growth of X. fastidiosa subsp.…”

“…The optimum in vitro growth temperature for the bacteria is 28 °C, and no growth of X. fastidiosa subsp. fastidiosa was observed in vitro at 12 °C (Feil and Purcell, 2001). Anas et al (2008) have shown the effect of warming temperature on disease severity, and mapped areas at risk of Pierce's disease by using the number of winter days with temperatures below -12.2 °C or -9.4 °C.…”