a cross-protection program citrus tristeza disease, caused by citrus tristeza virus (ctv) has been developed in the parana state, to obtain pera orange mother plants. thus, 20 plants were selected in the orange commercial fields of the north and northwest region. comparisons between mild and severe recognized isolates were made. the results showed mild-to-moderate stem pitting symptoms and the great majority of the isolates grouped up with the mild control isolate. these results suggest that the plants selected were infected by ctv mild haplotypes showing that they have mother plant potential.
