Characterization of resistance against the olive‐defoliating Verticillium dahliae pathotype in selected clones of wild olive

Abstract

Verticillium wilt of olive is best managed by resistant cultivars, but those currently available show incomplete resistance to the defoliating (D) Verticillium dahliae pathotype. Moreover, these cultivars do not satisfy consumers' demand for high yields and oil quality. Highly resistant rootstocks would be of paramount importance for production of agronomically adapted and commercially desirable olive cultivars in D V. dahliae‐infested soils. In this work, resistance to D V. dahliae in wild olive clones Ac‐13, Ac‐18, OutVert and StopVert was assessed by quantifying the fungal DNA along the stem using a highly sensitive real‐time quantitative polymerase chain reaction (qPCR) protocol and a stem colonization index (SCI) based on isolation of V. dahliae following artificial inoculations under conditions highly conducive for verticillium wilt. Ac‐13, Ac‐18, OutVert and StopVert showed a symptomless reaction to D V. dahliae. The mean amount of D V. dahliaeDNA quantified in stems of the four clones ranged from 3.64 to 28.89 pg/100 ng olive DNA, which was 249 to 1537 times lower than that in susceptible Picual olive. The reduction in the quantitative stem colonization of wild olive clones by D V. dahliae was also indicated by a sharp decrease in the SCI. Overall, there was a pattern of decreasing SCI in acropetal progression along the plant axis, as well as correlation between positive reisolation and quantification of pathogen DNA. The results of this research show that wild olive clones Ac‐13, Ac‐18, OutVert and StopVert have a valuable potential as rootstocks for the management of verticillium wilt in olive.

Heterologous Expression of the AtNPR1 Gene in Olive and Its Effects on Fungal Tolerance

“…Disease reactions to the D and ND V. dahliae pathotypes of three AtNPR1 transgenic lines as well as the non-transgenic control P1, which is highly susceptible to this pathogen (Narvaez et al, 2018), were assessed as previously described (Jiménez-Fernández et al, 2016). Monosporic V. dahliae isolates from cotton (V-138: D pathotype, race 2) and olive (V-1242: ND pathotype, race 2; and V-1558: ND pathotype, race 1) (Jiménez-Díaz et al, 2017) were used.…”

Tolerance of olive (Olea europaea) cv Frantoio to Verticillium dahliae relies on both basal and pathogen‐induced differential transcriptomic responses

“…Within this holistic framework, the use of tolerant/resistant olive varieties is probably the most efficient and environmentally friendly approach to control VWO. Several studies have focused on the search for sources of genetic resistance to V. dahliae (López‐Escudero et al ., ; Martos‐Moreno et al ., ; Antoniou et al ., ; Colella et al ., ; Trapero et al ., , ; García‐Ruiz et al ., ; Arias‐Calderón et al ., ,b; Jiménez‐Fernández et al ., ), although no cultivar/genotype has been reported as entirely resistant to the pathogen. Some genotypes have been qualified as tolerant (i.e.…”

Interactions between Trichoderma harzianum and defoliating Verticillium dahliae in resistant and susceptible wild olive clones

“…The newly developed V. dahliae YFP transformant proved suitable for the study because it did not show any difference compared with the wild type strain V. dahliae V‐138I regarding morphology and growth rate on different culture media. The transformant strain retained the parental virulence phenotype, as shown by the severe defoliation and plant death (mean symptoms severity = 4 on a 0–4 rating scale) induced on susceptible Picual olive 7 weeks after inoculation, a disease reaction similar to that found for the parental isolate on Picual olive in previous work (Jiménez‐Díaz et al ., ; Jiménez‐Fernández et al ., ). Also, no significant differences ( P ≥ 0.05) were found in the antagonistic ability of T. harzianum GFP22 against V. dahliae V‐138I and V. dahliae V138I‐YFP.…”

“…However, most commercial olive cultivars lack suitable resistance to the highly virulent D pathotype of V. dahliae that has become widespread in Spain and also occurs elsewhere (Jiménez‐Díaz et al ., ; Trapero et al ., ). In previous studies, three wild olive clones were identified that proved resistant to D V. dahliae , and these are used as rootstock for grafting D V. dahliae ‐susceptible olive cultivars in commercial production (Jiménez‐Fernández et al ., ; Palomares‐Rius et al ., ). Here, the potential of combining T. harzianum with use of a resistant wild olive rootstock was investigated for enhancing the integrated management of D V. dahliae ‐induced VW in olive.…”

“…europaea var. sylvestris ) rootstocks that have shown a high degree of resistance to D V. dahliae (Jiménez‐Fernández et al ., ; Palomares‐Rius et al ., ; Jiménez‐Díaz et al ., ), together with root treatments with biological control agents (BCAs; Tjamos et al ., ; Jiménez‐Díaz et al ., ).…”