1. DISEASE RESISTANCE AND PATHOGEN COLONIZATION OF OLIVE CULTIVARS INOCULATED WITH VERTICILLIUM DAHLIAE
C. Trapero.1, J. Romero1, B. Koopmann2, P. Karlovsky2, A. Von Tiedemann2, A. Trapero1, D. Barranco1 and F. J. López-Escudero1.
1Departamento de Agronomía, Universidad de Córdoba, 14014, Córdoba, Spain.
2Department für Nutzpflanzenwissenschaften, Georg-August Universität, Göttingen, Germany.
INTRODUCTION
The fungus Verticillium dahliae is the causal agent of Verticillium wilt of olive (Olea europaea), which is nowadays the main disease in most olive-producing countries. Control of the disease is very difficult to achieve, especially when very virulent isolates (defoliating pathotype) are present. Thus, the use of resistant cultivars is currently the most efficient measure. The objective of this work was to study the relationship between disease symptoms showed by different olive cultivars and their colonization carried out by the pathogen, as well as to provide some insights in the mechanisms of resistance to this pathogen.
MATERIALS AND METHODS
Olive plants of cultivars ‘Picual’ (very susceptible), ‘Arbequina’ (moderately susceptible) and ‘Frantoio’ (resistant), were inoculated with a highly virulent isolate (defoliating) of V. dahliae. Amount of pathogen DNA in roots and stems of infected plants were measured every 2 weeks after inoculation, starting one week after inoculation and ending at 15 weeks after inoculation. Disease severity was weekly assessed.
INOCULATION OF PLANTS
Disease severity assessment every week
ROOT AND STEM SAMPLING EVERY 2 WEEKS
QUANTITATIVE DETERMINATION OF PATHOGEN DNA IN SAMPLES
CULTIVARS: ‘Picual’ (highly susceptible), ‘Arbequina’ (moderately susceptible) and ‘Frantoio’ (resistant)
0-4 disease severity scale
3 inoculated and 3 control plants per cultivar
RESULTS
‘PICUAL’ (susceptible)
‘ARBEQUINA’ (Mod. Susceptible)
‘FRANTOIO’ (resistant) 4 3 2 1
Disease severity 4 3 2 1
Disease severity 4 3 2 1
Disease severity
Disease severity was very high in susceptible cultivars and most of the plants were killed 90 days after inoculation; while almost no symptoms were scored in the resistant one (‘Frantoio’).
Correlation between disease severity and amount of pathogen DNA in stems
Corr. coefficient
P value
‘Picual’
0.46
0.037
‘Arbequina’
0.38
0.094
‘Frantoio’
0.59
0.005
The amount of pathogen DNA in the roots decreased over time from the first week after inoculation, and there were only slight differences between cultivars.
Amount of pathogen DNA in stems increased over time, especially in susceptible cultivars. The amount was significantly lower in stems of the resistant cultivar compared with stems of the susceptible cultivars.
CONCLUSIONS
Verticillium dahliae is able to colonize the roots of all cultivars during the first weeks after the inoculation, but not to extensively colonize the stem xylem of the resistant cultivar ‘Frantoio’. Histological changes related with pathogen resistance are being studied.
REFERENCES
ACKNOWLEDGEMENTS
1. López-Escudero, F.J. & Mercado-Blanco, J. 2011: Verticillium wilt of olive: A case study to implement an integrated strategy to control a soil-borne pathogen. Plant and Soil. 344:1-50.
This research was partially granted by the Project AGL from the Ministerio de Ciencia e Innovación and by a grant of PhD student Carlos Trapero in Göttingen, Germany.
2. Markakis, E.A., Tjamos, S.E., Antoniou, P.P., Roussos, P.A., Paplomatas, E.J. & Tjamos, E.C. 2010: Phenolic responses of resistant and susceptible olive cultivars induced by defoliating and nondefoliating Verticillium dahliae pathotypes. Plant Disease. 94:
3. Mercado-Blanco, J., Collado-Romero, M., Parrilla-Araujo, S., Rodríguez-Jurado, D. & Jiménez-Díaz, R.M. 2003: Quantitative monitoring of colonization of olive genotypes by Verticillium dahliae pathotypes with real-time polymerase chain reaction. Physiological and Molecular Plant Pathology. 63: