The objectives of this work were to establish appropriate methodologies for isolation and inoculation of Septoria lactucae in order to evaluate resistance. Nine lettuce (Lactuca sativa) cultivars (Vitória-de-Santo-Antão, Uberlândia 10.000, Maioba, Elba, Aurélia, Black Seeded Simpson, Grand, Rapids, Salad Bowl-Mimosa and Babá de Verão) were screened for resistance to this pathogen under greenhouse and field conditions. The best results obtained were: a) for isolation: to transfer cirrus of conidia directly to the surface of Petri dishes with PDA medium plus antibiotics (streptomycin, chloramphenicol, ampicilim and riphampicin); b) for inoculation: to spray plants of six to eight leaves with a conidia suspension of 1 x 10(4) spores/ml and keep them in a moist chamber for 48 h. Significant differences were found among cultivars both in greenhouse and field tests. Under both conditions the cultivars Maioba and Vitoria de Santo Antão were found to be, respectively, the most susceptible and the most resistant cultivars among those tested. From these results, the greenhouse test methodology is seen to ge highly promising for the rapid screening of a great number of genotypes in breeding programs of lettuce resistant to S. lactucae.
