During June and July 1999-2000, a disease causing severe losses of seedlings of a local ecotype of lentil (Lens culinaria Medik, syn. Lens esculenta Moench.) was observed in four commercial fields in central Italy (Umbria and Latium regions). Disease symptoms, observed in both years, included stunting, wilting, marked reduction of root system, and internal vascular discoloration of the lower stem. Twenty-five samples for each field, consisting of lentil roots and stems, were collected. Seven to eight tissue pieces per sample, derived from the lower stem and a variety of root sizes, were sampled, surface-treated in 1 or 0.1% HgCl2 for 30 s, rinsed in sterile deionized water, placed on petri dishes containing potato dextrose agar (PDA, pH 5.5) and then incubated for 7 days at 25°C. F. oxysporum (2) (identification confirmed by R. A. Samson, Centraalbureau Voor Schimmelcultures of Baarn, Netherlands) was consistently recovered from affected tissues. Monoconidial cultures of four isolates were prepared and evaluated for pathogenicity. Seventy 4-week-old lentil seedlings (local ecotype) were inoculated by dipping the root system of each seedling in a spore suspension of each isolate of F. oxysporum (106 conidia/ml) for 30 min and transplanted into a pot containing a sterilized sandy-loam soil mix. In a second experiment, 100 seeds for each isolate were sown in the same soil mix amended with rice kernels colonized with four isolates of F. oxysporum (10% wt/wt). Seedlings dipped in sterile deionized water and seeds sown in soil amended with noncolonized rice kernels served as controls in the first and second experiments, respectively. Three replications of both pathogenicity tests were carried out in a controlled growth chamber at day/night 22/20 ± 2°C, 60/70% RH, 12 h day (180 μE•m2•s-1). Both experiments were repeated. Two to three weeks after inoculation, all plants inoculated with each F. oxysporum isolate showed the same symptoms observed in the field and caused wilting and death of 80 to 100% of the inoculated plants. F. oxysporum was consistently reisolated from the symptomatic test plants, whereas the fungus was never isolated from all control plants which remained symptomless and healthy. F. oxysporum was not observed in seed health tests (blotter and agar plate methods) carried out on 100 seeds per sample harvested from infected crops. Management practices include long-term crop rotation with nonsusceptible hosts and removal and destruction of infected crop debris. Seed treatment with fungicides (benzimidazoles, thiram) (3) can reduce incidence of the disease but host resistance is the best mean of controlling Fusarium wilt. Most resistant lentil accessions come from Chile, Egypt, India, Iran, and Romania (1). This is the first report of F. oxysporum f. sp. lentis on lentil in Italy. Without adequate control, this seedling disease may become a major factor limiting production of high quality lentils in Umbria and Latium.
References: (1) B. Baya et al. Euphytica 98:69, 1997. (2) C. Booth. C.M.I. Description of Fungi and Bacteria. No. 271, 1971. (3) J. Kannayan and Y. L. Nene. Indian J. Plant Prot. 2:80, 1974.