Potential Inoculum Sources of Phaeomoniella chlamydospora in South African Grapevine Nurseries

Abstract

Petri disease of grapevine is primarily caused by Phaeomoniella chlamydospora. This pathogen affects mostly young grapevines, but is also implicated in esca disease of older grapevines. Little is known about the disease cycle of this fungus. Infected propagation material was identified as a major means of dissemination of the pathogen. Recently, the pathogen was also detected from soil in South Africa and airborne conidia have been found in vineyards. The aim of this study was to use a molecular detection technique to test different samples collected from nurseries in South Africa at different nursery stages for the presence of P. chlamydospora. A one-tube nested-PCR technique was optimised for detecting P. chlamydospora in DNA extracted from soil, water, callusing medium and grapevine wood. The one-tube nested-PCR was sensitive enough to detect as little as 1 fg of P. chlamydospora genomic DNA from water and 10 fg from wood, callusing medium and soil. PCR analyses of the different nursery samples revealed the presence of several putative 360 bp P. chlamydospora specific bands. Subsequent sequence analyses and/ or restriction enzyme digestions of all 360 bp PCR bands confirmed that all bands were P. chlamydospora specific, except for five bands obtained from callusing media and one from water. Phaeomoniella chlamydospora was positively detected in 25% of rootstock cane sections collected from mother blocks, 42% of rootstock cuttings and 16% of scion cuttings collected during grafting, 40% of water samples collected after pre-storage hydration, 67% of water samples collected during grafting, 8% of callusing medium samples and 17% of soil samples collected from mother blocks. These media can therefore be considered as possible inoculum sources of the pathogen during the nursery stages.

PCR-Based Strategy To Detect and Identify Species of Phaeoacremonium Causing Grapevine Diseases

“…PCR amplifications carried out from wood extract are being performed to detect Phaeomoniella chlamydospora (16,28,33), the other important pathogen associated with Petri disease (4). It has been used to detect this pathogen in rootstocks and grapevine propagation plants (30), and it has shown the potential sources of Phaeomoniella chlamydospora in plant nurseries (29). Sim- Table 1.…”

“…Infection may take place in plant nurseries during the propagation process and storage (29,37). It may also happen because of the use of infected mother plants (10,12).…”

Advances in Propagation of Grapevine in the World

“…Aroca et al (2010) found viable Phaeoacremonium spp., Phaeomoniella chlamydospora and Cadophoraluteoolivaceae propagules in pruning shears, grafting machines and peat used for callus formation. Likewise, Retief et al (2006) verified that the increase in the incidence of Phaeomoniella chlamydospora at the rooting site occurred due to contamination in the pre-storage hydration phase. Waite and Morton (2007) verified that contamination at this stage was derived from fungal structures from mother plants.…”

“…However, Gramaje and Di Marco (2015), in a survey conducted in 146 nurseries in Europe, pointed out that hydration was performed prior to cold storage, but that the hydration time was variable, from one hour to more than 24 hours. Different species of trunk fungi have been detected in this water, and contamination can come from the plant material that brings the inoculum from the field or by the poor hygiene of tanks (RETIEF et al, 2006;AROCA et al, 2010;AGUSTÍ-BRISACH et al, 2011;WAITE et al, 2013). Gramaje and Di Marco (2015) also observed that the use of chemicals in hydration varied among nurseries.…”

An Integrated Strategy for the Proactive Management of Grapevine Trunk Disease Pathogen Infections in Grapevine Nurseries

“…& Mugnai) Crous & W. Gams and Phaeoacremonium species that cause Petri disease (Halleen et al, 2003;Mostert et al, 2006a), as well as species within the Botryosphaeriaceae family that cause wood necrosis and dieback (Van Niekerk et al, 2004;. Propagation material taken from apparently healthy mother vines can already be infected by these pathogens prior to grafting (Fourie & Halleen, 2002;Halleen et al, 2003;Aroca et al, 2010) or become infected during the different nursery processes, mainly through the large number of wounds made (Halleen et al, 2003;Retief et al, 2006;Aroca et al, 2010;Gramaje & Armengol, 2011;Agustí-Brisach et al, 2013). Pleurostomophora richardsiae (Nannf.)…”