Suppression of Verticillium Wilt of Olive by Pseudomonas fluorescens

Abstract

Protection of pathogen-free olive planting material from infection by Verticillium dahliae during plant propagation and/or at planting would help in the management of Verticillium wilt of olive. Despite the importance for rhizosphere functioning, rhizobacterial Pseudomonas spp. have been mainly studied in a cultivation-based manner. In this study, 8 isolates of Pseudomonas fluorescens obtained from roots of olive plants were tested for suppression of Verticillium wilt in nursery-produced olive planting stocks under controlled conditions. The antagonistic activity of P. fluorescens isolates from olive against defoliating (D) and nondefoliating (ND) V. dahliae pathotypes. The isolates of P. fluorescens isolates from olive varied in the ability to inhibit hyphal growth of D and ND V. dahliae on PDA. In planta bioassays were conducted under greenhouse conditions, by inoculating bacterial-treated and -nontreated 3-to 4-month-old, own-rooted plants of susceptible olive cv. Zard with the highly and less virulent V. dahliae. Results indicated that root treatment with some of P. fluorescens isolates significantly reduced the final disease incidence and severity, compared with the nontreated controls. Our results indicate that root treatment of olive plants with selected P. fluorescens isolates during nursery propagation can help in the biocontrol of V. dahliae in olive especially for ND pathotypes. No correlation was found between efficacy of tested bacterial isolates for in vitro antagonism of the pathogen and in planta suppression of Verticillium wilt.

The Role of Microbial Inoculants on Plant Protection, Growth Stimulation, and Crop Productivity of the Olive Tree (Olea europea L.)

“…Many strains of Bacillus and Pseudomonas have been used in agriculture as biocontrol agents against several diseases caused either by fungi or bacteria [ 54 ]. Sanei [ 55 ] reported that eight isolates of Pseudomonas fluorescens inhibited Verticillium ’s microsclerotia germination. The long-term endurance of microsclerotia and the fact that they cause the initial infections, make them direct targets of biocontrol of Verticillium dahliae [ 15 , 55 ].…”

“…Sanei [ 55 ] reported that eight isolates of Pseudomonas fluorescens inhibited Verticillium ’s microsclerotia germination. The long-term endurance of microsclerotia and the fact that they cause the initial infections, make them direct targets of biocontrol of Verticillium dahliae [ 15 , 55 ]. Furthermore, Markakis et al [ 56 ] showed that the application of Paenibacillus alvei K165 was also associated with the reduction of microsclerotia germination.…”

Belowground Microbiota and the Health of Tree Crops

“…Strains of Pseudomonas spp. have been isolated from the olive rhizosphere (and elsewhere), and proved to suppress VWO in young, nursery-produced plants (Mercado-Blanco et al, 2004 ; Sanei and Razavi, 2011 ; Triki et al, 2012 ; Gómez-Lama Cabanás et al, 2018 ). One of the best known BCA against VWO is P. fluorescens PICF7 (Prieto et al, 2009 ; Martínez-García et al, 2015 ).…”

Endophytic colonization and biocontrol performance of Pseudomonas fluorescens PICF7 in olive (Olea europaea L.) are determined neither by pyoverdine production nor swimming motility

“…For instance, application of microbial antagonists in pathogen‐free certified olive plants during the propagation process at nurseries has been proposed (Tjamos, ). There are only few reports on the identification and characterization of potential BCAs against VWO, although mostly preliminary or showing limited success (Müller et al ., ; Aranda et al ., ; Sanei and Razavi, ; Mercado‐Blanco and López‐Escudero, ). Moreover, very little is known about the mechanisms involved in biocontrol activity exerted by these microbes.…”