Lamb’s lettuce (Valerianella olitoria): new host of Fusarium oxysporum f. sp. conglutinans

A new wilt of lamb’s lettuce (Valerianella olitoria) was detected in northern Italy in 2003 and the causal agent of the disease was identified as Fusarium oxysporum. Pathogenicity tests and vegetative compatibility analysis were carried out on different isolates of the fungus. The pathogenicity of six isolates was tested on radish (Raphanus sativus), wild (Diplotaxis tenuifolia) and cultivated (Eruca sativa) rocket, cabbage (Brassica oleracea var. sabauda), cauliflower (Brassica oleracea var. botrytis), Brussels sprout (Brassica oleracea var. gemmifera), broccoli (Brassica oleracea var. italica), and turnip (Brassica rapa var. rapa). The results indicated that isolates of F. oxysporum from lamb’s lettuce belong to the forma specialis conglutinans. Vegetative compatibility grouping analysis showed the presence of VCG 0101 pathogenic on lamb’s lettuce. Among the 12 isolates from lamb’s lettuce tested, 10 belongs to VCG 0101 and are classified as F. oxysporum f. sp. conglutinans, while two are self-incompatible.