Abstract

Rootstocks highly resistant to the highly virulent Verticillium dahliae defoliating (D)pathotype would be of much interest for the management of Verticillium wilt in olive andgrowing of Verticillium-susceptible olive cultivars in geographic areas where D V. dahliaeprevails. Recently, research done at the University of Bari, Italy, and University of Córdoba,Spain, have led to the identification of some wild olive genotypes that could be of use asresistant rootstocks, including the currently patented clones STOPVERT and OUTVERT,AC13 and AC18. To further characterize the resistance reaction shown by those genotypesin previous studies, we have carried out a series of experiments using standardizedprotocols and controlled conditions optimal for development of Verticillium wilt. Own-rootedplants of a range of ages were inoculated with a range of high inoculum concentrations ofselected, highly virulent D isolate V138I by root dipping and/or transplanting in an artificiallyinfested soil mixture. Plants were inoculated once or twice in a sequence, and incubated inthe growth chamber for 3 to 4 months under optimal conditions for disease development.Disease reaction was assessed by the development of foliar symptoms, isolation of thepathogen from the lower, middle, and upper main stem, and molecular quantification of thefungus in the sampled tissues using a real-time quantitative PCR (qPCR) protocol with adetection limit of 18 fg of V. dahliae DNA in infected, symptomless tissues. ClonesSTOPVERT and OUTVERT showed a symptomless reaction to inoculation compared with100 % dead plants in susceptible 'Picual' olive and mild disease reaction in tolerant'Frantoio'. V. dahliae was isolated from middle stem parts of STOPVERT and OUTVERTplants to a lesser extent than from the lower stem, but isolations from 'Frantoio' plantsyielded the fungus from all stem parts at similar proportions. On average, the concentrationof V. dahliae DNA per 100 ng of stem DNA ranged from 5.6 to 41.1 pg in STOPVERTplants, from 13.7 to 80.9 pg in OUTVERT plants, and from 94.6 to 141.6 pg in 'Frantoio'plants. The larger of those concentrations is 120 times lower than that found in susceptible'Picual' olive. Extending the time of incubation of infected STOPVERT and OUTVERTplants reduced the frequency of successful isolations and quantification from previouslyinfected tissues. Clones AC13 and AC18 also showed a highly resistant reaction to root-dipinoculation with V. dahliae 138I, though slight symptoms developed in some 'AC18' plants.Average V. dahliae DNA concentration per 100 ng of stem DNA was 10,9 and 86,7 pg in'AC13' and 'AC18' plants, respectively, compared with 42,9 pg and 16,6 ng in 'Frantoio' and'Picual' olives. Histopathological assessment of the plants reaction is in progress. Also,experiments are being conducted to determine the influence of genetic and geographicdiversity of D V. dahliae isolates on the resistant

Autore Pugliese

• Bubici Giovanni Nicola

Tutti gli autori

• Jiménez-Fernández D.; Trapero-Casas J.L.; Gramaje D.; Landa B.B.; Navas-Cortés J.A.; Bubici; G.; Cirulli M.; Jiménez-Díaz R. M.

Titolo volume/Rivista

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Anno di pubblicazione

2013

ISSN

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ISBN

978-3-941261-12-9

Numero di citazioni Wos

Nessuna citazione

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Settori ERC

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