The expansion of the melon (Cucumis melo L.) fields in the Brazilian Northeast favored the occurrence of diseases such as the Myrothecium stem canker caused by the fungus Myrothecium roridum. In order to select genotypes with potential use in genetic breeding programs and in integrated disease management, 150 melon genotypes were evaluated. Twenty-two day old melon plants cultivated under greenhouse conditions were pierced in the crown and inoculated with a pathogen suspension (3x10(6) conidia/ml). The evaluations were done daily, with the aid of a descriptive scale varying from 0 to 4, until six days after the moist chamber had been removed. The genotypes were distributed in five classes of disease reaction using data of the last evaluation. None of the genotypes were immune or highly resistant to the disease, 26.7% were intermediate resistant (IR) and 73.3% were susceptible (S) or highly susceptible (HS). These results illustrate the difficulties in obtaining genetic sources with high levels of resistance to M. roridum. The groups Cantaloupe, Charentais, Galia and Undefined showed the largest frequency of genotypes with IR reaction and the smallest frequency of HS genotypes. Most of the genotypes of the groups Yellow Valencian (66.7%), Cantaloupe (57.4%), Galia (60.0%) and 'Undefined' (53.8%) were susceptible. The genotypes 'PL 420149', 'Caroline', 'A3', 'Chilton' and 'PS-1 Pele de Sapo' showed the lowest values of disease severity and are promising resistance sources to the pathogen, and should be preferred in commercial fields subject to the disease.
Cucumis melo; Myrothecium stem canker; genetic resources
