ABSTRACT
Fusarium oxysporum, Verticillium dahliae and a hypovirulent isolate of Phoma tracheiphila were used to induce resistance to Citrus mal secco in sour orange seedlings. The tests were performed in a growth chamber using 1-2 year old sour orange seedlings. The isolates were inoculated simultaneously , 15 days 1,2,4 months before the inoculation of the virulent isolate of Phoma tracheiphila. Only the hypovirulent isolate induced resistance to mal secco: protection was observed when one month elapsed between the first and second inoculation; and, the greater the time interval between the two inoculations, the greater the protection. The results obtained seem to suggest that the control of mal secco by inducing resistance with inoculations of a hypovirulent isolate of the pathogen is promising and deserves further research.
