2.2.4 Discussion
Paenibacillus isolates differed in their ability to suppress the growth of Xcc isolates in vitro. Differences
in the genetic backgrounds of the Paenibacillus isolates are likely to have contributed to this variation.
For the 25 Paenibacillus isolates, based on DNA sequence variation the 16S rRNA gene represented 11
different species of which six displayed activity against Xcc. Even among species there was considerable
variation in the bioactivity of the isolates. For example, the activity of P. polymyxa ranged from none
31 to suppressive activity against three or four different combination of Xcc isolates. Genetic variation
among P. polymyxa isolates was reported by Phi et al. (2010) using BOX-PCR which classified the
isolates into five groups with different antagonistic activity against E. caratovora subsp. carotovora
and X. axonopodis pv. vesicatoria.