In a previous study, Streptomyces strain NSP3 was selected from the strong activity
in vitro antifungal activity against various plant pathogenic fungi, and Fusarium oxysporum f.
sp. lycopersici (Fol) isolate FolCK_117. In this study, Streptomyces NSP3 was shown to be a
biotic elicitor of priming agents that initiated plant defense responses to Fusarium wilt disease
in tomato cv. ‘Bonny Best’. The effects of seed treatment or soil application with the NSP3
and combination of the two methods were compared against challenge inoculation with
FolCK_117. The recognition event leading to expression of some plant defense-related genes,
including PR-1a, Chi3, Chi9 and CEVI-1, was analyzed using real-time quantitative PCR
(qPCR) and normalized to the Actin gene at 0, 3, 6, 12 and 24 h post-inoculation (hpi). The
results implied that plants had strategy involved inducible defense reactions which are activated
after elicitor applications within 24 hpi. Combination of two described methods above was
more effective for induction and accumulation of these PR proteins than either alone. Gene
expression of PR-1a was increased to maximum (73.1 fold) at 3 hpi. Gene expression of Chi3
was remarkably increased at 24 hpi to 56.1 fold. Gene expression of Chi9 and CEVI-1 were
likewise increased to maximum at 12 hpi (50.7 and 43.3 fold, respectively). These results
suggested that Streptomyces NSP3 was a strong elicitor of plant defense responses.
Understanding the bioactive component of defense induction may lead to a control strategy for
Fusarium wilt disease in tomato.