Zoospores are the main weapons for infecting plants by most
phytopathogenic peronosporomycetes and thus inhibition of zoospore
production andmotility inhibition often reduces disease incidence and
severity (Islam and von Tiedemann, 2011). In present study, all three
Pseudomonas spp. remarkably inhibited development of sporangia,
release and motility of the zoospores in vitro (Fig. 3). However, in vivo
disease suppression may have been influenced by similar mechanism
if the bacteria release similar active products in the rhizpsphere. As the
in vitro bioassay in this study revealed that both live bacteria (added
before dark treatment) and their cell-free culture supernatant (before
cold treatment) could inhibit zoospore release, both inhibition of
mycelial growth and production of zoospores by the bacteria might
have been linked to suppression of damping-off disease in cucumber
due to seed inoculation with antagonists. Similar results have been
reported earlier by Nakayama et al. (1999) and Islam et al. (2005).