Evaluation continues

Evaluation continues

Evaluation continues

Candidate

V. dahliae microsclerotia in infested soil or mycelia in the vascular rings of symptomless planting material (off-shoots or stumps) are the only inocula giving rise to disease in artichokes. Verticillium wilt is a monocyclic disease, i.e., it has only one cycle of pathogenesis per cropping season and the resulting inoculum does not give rise to new infection and disease within the same season. The epidemiology of Verticillium wilt diseases is driven mainly by inoculum density in soil. In addition, the ability of V. dahliae to infect many weed species may play an important role in the epidemiology of Verticillium wilts. Weeds may serve as alternative hosts contributing to maintenance or even increase of V. dahliae inoculum in soil (Cirulli et al., 2010).
Verticillium albo-atrum and V. dahliae cause wilting and sometimes death of plants. Verticillium wilt is a cool-weather disease and has a wide host range in natural areas. The two Verticillium spp. survive in soil, as long lived resting mycelium or microsclerotia, respectively, or in debris from infected plants. Control is by use of healthy planting material, partial resistant cultivars (for artichoke), prevention of movement of infected plants and infested soil, removal of diseased plants and plant debris, avoiding high nitrogen concentrations and soil disinfestation. Crop rotation can reduce losses, but not eliminate the pathogens because of the wide host range of Verticillium spp. (EPPO, 2004). Bell pepper was found resistant to all V. dahliae isolates except those from pepper or eggplant in one paper, but in two other papers found little host specificity existed in isolates of V. dahliae and V. alboatrum, so crop rotation would not assist in control. In general, natural populations of V. dahliae are conceived as host adapted rather than host specific, i.e., they display cross pathogenicity but are more virulent to the host from which they were isolated. Pathogenicity of artichoke isolated was investigated and, in some cases, preferential hosts were found (cardoon, eggplant, melon, watermelon). Pepper, tomato, cucumber were not always affected by artichoke isolates (Cirulli et al., 2010).
Regarding the wide host range and longevity of inoculum sources in the environment, planting material (transplants) are not considered to be the main pathway for introduction. However because artichoke is not produced using seeds (using vegetative propagation from mother plants, grown in open fields), and because rotation is available for this crop, experts agreed that plant for planting could be considered as a significant pathway compared to other pathways.

Yes

Severe wilt problems caused by Verticillium dahliae Kleb. are frequently observed in artichoke (Cynara cardunculus var. scolymus) grown in South Italy, Spain, and Chile, where diseased plants do not produce at all or give only few small and deformed heads (Temperini et al., 2010). In Eastern Spain, Verticillium wilt caused by V. dahliae is now recognized as one of the major problems limiting yield in artichoke crops (Cynara cardunculus var. scolymus [C. scolymus] (Ortega & Perez, 2007). Armengol et al. reported over 80% disease prevalence in Spanish fields of stump- and seed-propagated artichokes sampled during 1999 to 2002, with an average wilt incidence of 53.8%.

Major

No

Candidate

candidate

Overall, Verticillium wilt caused by V. dahliae is difficult to manage, and no single disease control measure is efficient enough if applied individually. The application of integrated management strategies that combine selection of planting site, disease risk assessment (e.g. assessment of the available inoculum in the soil, determination of pathotypes/races/VCGs present in the site, cropping history of the field, etc.), cultural practices, such as crop rotation and manipulation of fertility and irrigation, use of healthy planting material, including seeds, use of available resistant cultivars and sometimes pre-plant soil treatments, such as solarisation, that reduce the viability of microsclerotia in soil (El-Zik, 1985; Shen, 1985; Bell, 1992; Jeger et al., 1996; Klosterman et al., 2009; Jiménez-Díaz et al., 2012) may reduce disease incidence and severity, but they do not eliminate the pathogen (EFSA, 2014).
In artichoke, the use of stump-propagated planting material should be reinforced by the establishment of fields of V. dahliae–free mother plants and the implementation of certification schemes. An alternative approach to reduce the risk of introducing the pathogen in non-infested soil would be the use of seed-propagated planting material (Cirulli et al., 2010).