NAME OF THE ORGANISM: Pelamoviroid latenspruni (Peach latent mosaic viroid) (PLMVD0)

Evaluation continues

Listed as 'Peach latent mosaic pelamoviroid' in EPPO Standard PM 4-30 Certification scheme for almond, apricot, peach and plum; and testing is recommended for P. persica. In responses to the questionnaire, EUROSEEDS, ES and PL supported deregulation in the EU. ES and EUROSEEDS argued that economic impact was acceptable. PL considered that plants for planting was not the main pathway. Evaluation continues on these criteria.
Remark: The assessment performed covers the given host species as well as interspecific hybrids with other Prunus species.

Candidate

The PLMVd infection was initially thought to be restricted to Prunus persica (Desvignes, 1986; Skrzeczkowski et al., 1996; Di Serio et al., 1999). More recently the viroid has been detected in other fruit trees including apricot, plum, sweet cherry, pear and mango and, also, in grapevine (Kyriakopoulou et al., 2017; Kaponi et al., 2024). In addition, more recently PLMVd infection has been reported in kaki and Johnsongrass (Oksal et al., 2021), and walnut (Tuncel et al., 2020). However, information on the relative accumulation levels or the prevalence in these alternative hosts is lacking as the corresponding reports are usually limited to the detection of the viroid in one or few samples through RT-PCR (Navarro et al., 2023).
Horizontal transmission of PLMVd occurs mainly by the propagation of infected buds; this has been the route for the worldwide spread of PLMVd, particularly considering that this pathogen was not included in most certification schemes until the early 2000’s (Flores et al., 2006).
PLMVd can also be locally dispersed plant to plant via pruning tools (the viroid has been experimentally transmitted with contaminated blades; Hadidi et al., 1997), and with a low efficiency by aphids (Desvignes, 1986; Flores et al., 1992).
PLMVd is not vertically transmitted through seed (Barba et al., 2007; Howell et al., 1998), but it is pollen-borne and pollen-transmitted (Barba et al., 2007). PLMVd was detected in supernatants and washed pollen from nine infected peach cultivars. Pollination of healthy plants with PLMVd-infected pollen transmitted the viroid at a rate dependent on peach cultivar: after 6 year, PLMVd was detected in five from the 18 plants experimentally pollinated, these five plants belonged to the same recipient cultivar (Barba et al., 2006; Flores et al., 2017).
The Fruit SEWG concluded that plants for planting was a significant pathway (transmission by grafting material and pollen are reported).

Yes

Although most infections occur without conspicuous symptoms, certain PLMVd isolates induce leaf mosaics, blotches and in the most extreme cases albinism (peach calico, PC; Malfitano et al., 2003), flower streaking, delays in foliation, flowering and ripening, deformations and discoloration of fruits (which usually present cracked sutures and enlarged roundish stones), bud necrosis, stem pitting and premature ageing of the trees (which also adopt a characteristic growing pattern, open habit) (Flores et al., 2006).
Peach latent mosaic disease can diminish fruit quality (due to skin discolorations and suture cracks), shorten longevity of trees, and makes the trees more susceptible to other stresses. Ironically, some PLMVd-incited symptoms, particularly flowering delay, protects against late frosts in specific geographic areas (Gibson et al., 2001), although the delayed fruit ripening may reduce the economic value (Flores et al, 2017).

Minimal to Medium

No

Candidate

Dependent on isolate the impact may be minimal to medium. Pollen transmission would allows a rapid pathogen dispersal, locally.
[EUROSEEDS considered that economic consequences of deregulation would be minimal, if managed at the stakeholders' level.]

Candidate

Healthy propagation material.

Candidate