Severe Verticillium dahliae attacks have occurred in artichoke crops in the Comunidad Valenciana region of eastern-central Spain since the late 1990s. Knowledge of genetic and virulence diversity in the pathogen population is a key factor for the management of the disease through disease risk assessment as well as development and use of resistant cultivars. V. dahliae isolates from artichoke (109 isolates) and cotton (three isolates) in that region were characterized by vegetative compatibility grouping (VCG), and specific polymerase chain reaction assays using three sets of primer pairs that differentiate the cotton-defoliating (D) and -nondefoliating (ND) V. dahliae pathotypes. In all, 35 and 39 V. dahliae isolates representative of the identified VCGs and geographic origins were tested for virulence to artichoke cvs. Nun 6374 and Nun 9444, and cotton cv. Acala SJ-2, respectively. Four VCGs were identified among 107 artichoke isolates, and 2 isolates were heterokaryon self-incompatible: VCG1A (one isolate), VCG2A (31 isolates), VCG2B (72 isolates), and VCG4B (three isolates). The three cotton isolates were VCG1A. Isolates in VCG2B were distributed across the region and were the most prevalent isolates in the northern part. Conversely, 83.9% of isolates in VCG2A were recovered from the southern part of the region. Two subgroups of isolates were identified in VCG2B based on heterokaryon compatibility with either international or local tester isolates, which further showed diversity in the amplification of 334- and 824-bp DNA fragments which are markers of the D and ND pathotypes, respectively. Virulence of isolates to artichoke and cotton correlated with VCG but the pattern of correlation varied with the host. VCG1A isolates from artichoke and cotton induced defoliation in cotton but not in artichoke. Collectively, isolates of VCG2B and VCG4B were the most virulent and isolates of VCG1A or HSI were the least virulent to artichoke; but isolates of VCG1A were more virulent to cotton than those of any other VCG. Also, molecular subgrouping in VCG2B determined by amplification of the 334- and 824-bp markers correlated with virulence of isolates to the two hosts tested.

The occurrence of fungal grapevine trunk pathogens associated with grapevine nurseries and the decline of young vines in Spain was determined in extensive surveys conducted in nurseries and vineyards with young plants. The presence of Phaeomoniella chlamydospora, Phaeoacremonium aleophilum, Cylindrocarpon spp., Botryosphaeria obtusa and Botryosphaeria spp. was detected in all the surveys that were carried out. This study provides evidence for the presence of these pathogens in Spanish grapevine nurseries. Cylindrocarpon spp., B. obtusa and Botryosphaeria spp., were isolated very early in the planting material production process, nevertheless, P. aleophilum and P. chlamydospora were not detected until the rootstock-scion combinations were planted in the field to develop shoots and roots during summer. The occurrence of trunk disease pathogens in symptomatic young vineyards was also high, suggesting that infected plant material might have been used. Phaeomoniella chlamydospora and P. aleophilum were the main species associated with the decline of young vines, followed by Botryosphaeria spp., Cylindrocarpon spp. and B. obtusa. This research confirmed the importance of fungal grapevine trunk pathogens associated with the decline of young vineyards in Spain and suggested the connection between the presence of these fungi in the nurseries and the disease in the fields. Halleen et al., 2004;Petit and Gubler, 2005) andBotryosphaeria spp. (causal agents of black dead arm;www.blackwell-synergy.com

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