First Report of Fusarium oxysporum on Eruca vesicaria and Diplotaxis spp. in Europe

Abstract

Two types of rocket are available on the market in Italy: (i) Eruca vesicaria (synonym E. sativa) known as ruchetta or cultivated garden rocket; and (ii) several species of Diplotaxis (Diplotaxis erucoides, D. muralis, and D. tenuifolia), which are wild plants now widely cultivated. Rocket is increasingly used in the mediterranean cuisine as salad and or to decorate dishes. In spring 2002, plants of the cultivated (E. vesicaria) and wild (Diplotaxis spp.) rocket showing symptoms of a wilt disease were observed in several commercial plastic greenhouses near Bergamo, in northern Italy. Wilted plants were first observed during the spring and summer of 2001 when temperatures were between 26 and 35°C. In May 2002, symptoms were again observed in the same area, on the same farm as well as other farms. Although the distribution of the disease was generally uniform, symptoms were more severe in the central part of the greenhouses where temperatures were warmest (30 to 60% of plants were affected). Diseased plants were stunted and chlorotic with brown or black streaks in the vascular system. Vascular tissues of affected plants appeared red or brown. Vascular streaks in the chlorotic leaves extended from the crown and were continuous with a red-brown discoloration in the vascular system of the crown and upper taproot. Fusarium oxysporum was consistently and readily isolated from symptomatic vascular tissues when plated on a Fusarium-selective medium (2). Microconidia measured 8.8 × 3.0 µm. E. vesicaria and Diplotaxis spp. were grown in steam-sterilized soil, and 10 days after emergence they were artificially inoculated by root dipping in a spore suspension (1 × 105 CFU/ml) of three F. oxysporum strains collected from infected plants. Uninoculated plants served as control. Plants (60 per treatment) were grown at 25 to 28°C in growth chambers. Wilt symptoms developed on all plants 20 days after inoculation, and F. oxysporum was consistently reisolated from infected plants. The pathogenicity test was conducted twice. To our knowledge, this is the first report of F. oxysporum on cultivated rocket in Europe and the first on wild rocket (Diplotaxis spp.) in the world. A wilt of E. sativa attributed to F. oxysporum f. sp. erucae was previously reported in India in 1973 (1). Studies are being carried out to determine if the Italian isolates of F. oxysporum belong to the same formae speciales. References: (1) C. Chatterjee and J. N. Rai. Indian Phytopathol 28:309, 1973. (2) H. Komada. Rev. Plant Prot. Res. 8:114, 1975.