The highest C/N ratio of plants grown in compost showed the lowest content of nitrogen in leaves, which would make the leaves more resistant to attack by the pathogen. Conversely, in a study with tomato plants with high C/N ratio makes plants more susceptible to the primary lesions formation caused by B. cinerea (Hoffland et al., 1999). The role of host nitrogen content in the susceptibility to B. cinerea is still unclear because there are other factors involved as N source and amount and B. cinerea isolates virulence (Lecompte et al., 2010).