The variability of 53 isolates of Myrothecium roridum obtained from melon (Cucumis melo) fields in the State of Rio Grande do Norte (Brazil) was estimated based on: severity of Myrothecium stem canker in the cultivars AF-682 and Orange Flesh, the pathogen's physiology (mycelium growth rate - MGR - and sporulation - SP) and its sensitivity to the fungicide fluazinam. All isolates were pathogenic to AF-682 and Orange Flesh; however, better discrimination of pathogen variability was achieved in the latter. Variation among isolates was high when assessing all variables, except for MGR and sensitivity to fungicides (all sensitive). There was no correlation between SEV and any other variables. The variation among isolates within municipalities (60%) was higher than the variation among municipalities. There is evidence of high genetic variability in the populations of M. roridum, but no association between the assessed variables and locations was detected.
Cucumis melo; Myrothecium stem canker; disease severity; sensitivity to fluazinam
