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Published December 4, 2019 | Version v1
Presentation Open

Insights into differential responses of olive cultivars to Xylella fastidiosa infections

  • 1. CNR, Istituto per la Protezione Sostenibile delle Piante, Bari (IT)

Description

Abstract: Xylella fastidiosa strain De Donno causes severe symptoms of desiccation on the
susceptible cultivars Ogliarola salentina and Cellina di Nardò. In the Xylella-ravaged olive groves,
survivor plants of cv Leccino have been identified and monitored since the beginning of epidemic
spread of X. fastidiosa in Apulia (southern Italy). Studies in field-grown plants (Giampetruzzi et al.,
2016) suggest that the resistance of these two cultivars relies on two pillars: a lower bacteria
population size compared with that of susceptible cultivars and, limited to Leccino, a differential gene
expression response that involves leucine rich receptor-like kinases (LRR-RLKs). Successive studies
with artificially infected olives under controlled conditions, showed that the same host responses
occurred when plants of the cvs Cellina di Nardò and Leccino were inoculated with the strain CO33,
taxonomically related to subsp. sandyi. Consistent with the previous data, transcripts of two LRRRLKs,
orthologous to At1g35710 and At4g08850, which are reported to regulate cell wall damage
response in Arabidopsis thaliana (Van der Does et al., 2017), were found overexpressed in Leccino.
Moreover, quantitative PCR assays targeting the At1g35710 olive orthologous gene showed an
increased expression in different olive cultivars artificially inoculated under controlled conditions.
Besides these molecular studies, the bacterial population sizes were estimated in different tissues of
the infected plants: leaves, young (Ø?5 mm) and hardwood cuttings (Ø?5 mm -?1 cm), and in tissues
collected from scions of different cultivars grafted onto the same rootstock. From these tests, further
evidence on the resistance of Leccino and FS17 were collected, with tissues of these cvs harbouring
lower bacterial titer than Ogliarola salentina (this was particularly evident in the leaves of the cv
Leccino) and not showing typical and severe desiccation phenomena, even when branches of these
cvs were co-grafted on the same rootstocks with scions of Ogliarola salentina showing severe
dieback. Further data on these double grafted olives and genetic achievements will be presented.

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Additional details

Funding

POnTE – Pest Organisms Threatening Europe 635646
European Commission
XF-ACTORS – Xylella Fastidiosa Active Containment Through a multidisciplinary-Oriented Research Strategy 727987
European Commission