6 research outputs found
Surplus zinc ameliorates the response of tobacco plants to Xylella Fastidiosa infectios
Trabajo presentado en la XXIV Reunión de la Sociedad Española de Biología de Plantas y XVII Congreso Hispano-Luso de Biología de Plantas, celebrados en Vigo (online) del 7 al 9 de julio de 2021.Xylella fastidiosa, (Xf), is a xylem-confined bacteria and a quarantine pathogen organism in the EU that causes important diseases in vineyards and almond tree orchards in Mallorca (Balearic Islands) (Gomila et al., 2019). Zinc is a key micronutrient that participates in the plant’s protection against pathogens (Cabot et al., 2019). The virulence of Xf is affected, among other factors, by plant ionic composition. Zinc concentration has been
related to planktonic growth and Xf biofilm production (Andersen et al., 2007; Navarrete et al., 2015). Here, the role of surplus Zn in the plant response to Xf has been studied in N. tabacum var. Petit Havana. Plants were grown in 50% Hoagland nutrient solution modified with 2 (control) or 12 μM (surplus Zn) Zn. In 2-month-old plants, the lowest non-senescent leaf in half of the plants for each Zn treatment were inoculated with Xf subp. fastidiosa. Forty days after inoculation, visual symptoms, plant biomass, and water content were recorded. Bacterial population in plant extracts was quantified by qPCR. Wilting symptoms were shown in the lower leaves of inoculated plants in both Zn treatments. Moreover, Xf accelerated flowering more markedly in control than in surplus Zn plants. In both Zn treatments, leaf fresh and dry biomass decreased in infected plants, with the exception of the youngest leaves in surplus Zn, which showed no differences with respect to control. Xf decreased water content in the leaves closest to the inoculation site, which showed the highest Xf colonization in both Zn treatments. Bacterial colonization decreased in the upper leaves, with surplus Zn plants showing the lowest values. Xf decreased total plant biomass in control plants, while no differences were found in the surplus Zn treatment. In surplus Zn, Xf-inoculated plants showed a significant increase in root growth with respect to control. Our results suggest that the ameliorating effect of surplus Zn in the response of tobacco plants to Xf could be related to promotion of the development of a larger root system, which could contribute to maintain plant growth, rather than surplus Zn having an inhibitory effect on bacterial colonization or improving leaf water status.This study is funded by the Regional Ministry of Agriculture, Fisheries and Food (Direcció General de Sanitat i Producció Agrària) of the Autonomous Government of the Balearic Islands and the Spanish Government (grant reference PID2019-104000-R).Peer reviewe
Improving Xylella sampling in Mallorca
Trabajo presentado en la 2nd European conference on Xylella fastidiosa (how research can support solutions), celebrada en Ajaccio el 29 y 30 de octubre de 2019.Xylella fastidiosawas detected in Majorca in late 2016 (Olmo et al. 2017). Since then, accomplishing EU regulatory, a huge number of samples have been analysed. Poster sessions71| P a g eParticularly, the Mallorca outbreak is different to others in Europe, because of the coexistence of subspecies multiplex(ST81, ST7) in almond trees, olive trees and other species, and subspecies fastidiosa(ST1) in almond trees and grapevine plants among others.As alreadyknown, detection tests of X. fastidiosaare conditioned by the sampling date. However, it is not well known if the optimal dates for sampling are the same for all host species, if it is viable to pool several samples, or if the bacterium can be detected in old wood samples.In this study, we have focused the X. fastidiosamonitoring on almond, grapevines and olive trees. Monthly percentages of positives and average Ct value of more than 2,000 analyses of each of these crops were compared. Overall, we observed that for almond trees the best results were obtained from samples collected from June to August, whereas in grapevine the optimum period was from August to October. In olive trees early spring resulted in the most favourable time for detection, with an increase in Ct and decrease of positive cases in summer.In the assays conducted with pooled almond leaf samples, mixing one infected plant extract with the same volume of up to four negative extracts, showed an average Ct increase of 2.7 cycles, whereas for olive and grapevine samples the Ct increase was > 4 cycles.By default, X. fastidiosais normally analysed in leaf midribs and petioles. We also tested the potential use of wood samples from trunks,sampling different tree rings. Although this sampling procedure is not recommended for routine surveys, it allowed us to establish a potential infection chronology of the number of years since the first infection might have occuredin the Balearic Islands.Study supported by Project E-RTA2017-00004-C06-02 from AEI-INIA Spain and FEDER and the Spanish Olive Oil Interprofessional
Phylogenetic inference enables reconstruction of a long-overlooked outbreak of almond leaf scorch disease (Xylella fastidiosa) in Europe
The recent introductions of the bacterium Xylella fastidiosa (Xf) into Europe are linked to the international plant trade. However, both how and when these entries occurred remains poorly understood. Here, we show how almond scorch leaf disease, which affects ~79% of almond trees in Majorca (Spain) and was previously attributed to fungal pathogens, was in fact triggered by the introduction of Xf around 1993 and subsequently spread to grapevines (Pierceʼs disease). We reconstructed the progression of almond leaf scorch disease by using broad phylogenetic evidence supported by epidemiological data. Bayesian phylogenetic inference predicted that both Xf subspecies found in Majorca, fastidiosa ST1 (95% highest posterior density, HPD: 1990–1997) and multiplex ST81 (95% HPD: 1991–1998), shared their most recent common ancestors with Californian Xf populations associated with almonds and grapevines. Consistent with this chronology, Xf-DNA infections were identified in tree rings dating to 1998. Our findings uncover a previously unknown scenario in Europe and reveal how Pierce’s disease reached the continent.This work was partially funded by projects XF-ACTORS (Xylella fastidiosa Active
Containment Through a Multidisciplinary-Oriented Research Strategy; grant 727987
from European Union’s Horizon 2020 Framework Research Programme) and ERTA2017-00004-02 and E-RTA2017-00004-04 (Desarrollo de estrategias de erradicación,
contención y control de X. fastidiosa en España) from ‘Programa Estatal de I + D + I
Orientada a los Retos de la Sociedad of the Spanish Government’ and FEDER) and from
the Organización Profesional del Aceite de Oliva Español’. M.P.V-A. was recipient of a
PhD fellowship from Intramural Project 201840E111from CSIC. A.B. was recipient of a
postdoctoral UIB contract funded by the Vicerectorado de Investigación e Internacionalización of the University of the Balearic Islands
Landscape Epidemiology of Xylella fastidiosa in the Balearic Islands
Xylella fastidiosa (Xf ) is a vascular plant pathogen native to the Americas. In 2013, it
was first reported in Europe, implicated in a massive die-off of olive trees in Apulia, Italy. This
finding prompted mandatory surveys across Europe, successively revealing that the bacterium was
already established in some distant areas of the western Mediterranean. To date, the Balearic Islands
(Spain) hold the major known genetic diversity of Xf in Europe. Since October 2016, four sequence
types (ST) belonging to the subspecies fastidiosa (ST1), multiplex (ST7, ST81), and pauca (ST80) have
been identified infecting 28 host species, including grapevines, almond, olive, and fig trees. ST1
causes Pierce’s disease (PD) and together with ST81 are responsible for almond leaf scorch disease
(ALSD) in California, from where they were introduced into Mallorca in around 1993, very likely via
infected almond scions brought for grafting. To date, almond leaf scorch disease affects over 81% of
almond trees and Pierce’s disease is widespread in vineyards across Mallorca, although producing on
average little economic impact. In this perspective, we present and analyze a large Xf -hosts database
accumulated over four years of field surveys, laboratory sample analyses, and research to understand
the underlying causes of Xf emergence and spread among crops and wild plants in the Balearic
Islands. The impact of Xf on the landscape is discussed
Landscape Epidemiology of Xylella fastidiosa in the Balearic Islands
[eng] Xylella fastidiosa (Xf) is a vascular plant pathogen native to the Americas. In 2013, it was first reported in Europe, implicated in a massive die-off of olive trees in Apulia, Italy. This finding prompted mandatory surveys across Europe, successively revealing that the bacterium was already established in some distant areas of the western Mediterranean. To date, the Balearic Islands (Spain) hold the major known genetic diversity of Xf in Europe. Since October 2016, four sequence types (ST) belonging to the subspecies fastidiosa (ST1), multiplex (ST7, ST81), and pauca (ST80) have been identified infecting 28 host species, including grapevines, almond, olive, and fig trees. ST1 causes Pierce's disease (PD) and together with ST81 are responsible for almond leaf scorch disease (ALSD) in California, from where they were introduced into Mallorca in around 1993, very likely via in- fected almond scions brought for grafting. To date, almond leaf scorch disease affects over 81% of almond trees and Pierce's disease is widespread in vineyards across Mallorca, although producing on average little economic impact. In this perspective, we present and analyze a large Xf-hosts da- tabase accumulated over four years of field surveys, laboratory sample analyses, and research to understand the underlying causes of Xf emergence and spread among crops and wild plants in the Balearic Islands. The impact of Xf on the landscape is discussed