%0 Journal Article %A Bennett, Robert A. %T Evidence for Two Virulence Determinants in the Fireblight Pathogen Erwinia amylovora %D 1980 %J Microbiology, %V 116 %N 2 %P 351-356 %@ 1465-2080 %R https://doi.org/10.1099/00221287-116-2-351 %I Microbiology Society, %X Seven avirulent strains of Erwinia amylovora were mixed in various combinations and tested for virulence. Only one combination, where the capsulated avirulent strain P66 was combined with the non-capsulated avirulent strain 4S2, induced fireblight symptoms in immature pear fruits and apple shoots. Growth studies in vivo strongly suggested that these strains were acting synergistically and that the non-capsulated strain possessed another, as yet unknown, virulence factor. %U https://www.microbiologyresearch.org/content/journal/micro/10.1099/00221287-116-2-351