Mapping the science around Xylella fastidiosa: An update after the outbreak on Italian olive groves

Xylella fastidiosa (Xf) is a plant pathogen which attacks vines, citrus fruits, olive, almond and several many other species, causing considerable economic losses. In the last few years Xf has become a global threat after being a local problem for decades: while it was once known only in circumscribed regions of the Americas, in 2013 it began to devastate olive groves in Southern Italy, and its presence has also been reported in France, Spain, and Portugal. Even though Xf has been under study since the late 1980s, the rapid worldwide spread raises the question of whether research infrastructure is adequately prepared to address new challenges, such as the need for novel methods to control and prevent Xf infection, gaining a deeper understanding of its biology and life cycle to identify vulnerable intervention points, coordinating international responses to combat its spread, and mitigating impacts on crops and the agricultural environment. Using a bibliometric approach, this study tried to answer this question by tracing an overview of the evolution of Xf literature from 1989 to present. The analysis was conducted on the Scopus database focusing separately on three periods (1989–1999; 2000–2010; 2011–2021). After a pioneering phase in 1989–1999, the intermediate period resulted the one with the highest scientific production, in which most currently ongoing research lines were started. The last period showed a revitalization of research after some years of decline, mostly due to the recent outbreak on olive in Europe, but it was characterized by a slower increment of topics with a growth of interconnection level among themes, indicating an ongoing process of consolidation of the established research lines. The authorship and thematic characterization demonstrated that Xf research was shaped by a "geographical factor", which has represented a crucial element over time and continues to have an impact on how collaborations and topics are organized.