Abstract: In our previous work, a strain of endophytic bacteria Bacillus subtilis DZSG23 was isolated from the leaves of Eucommia ulmoides Oliv, which could effectively control the wheat scab. This study was carried out to explicit the resistance mechanism of endophytic bacteria DZSG23 against wheat scab.The colonization property of DZSG23 in wheat was analysed by antibiotic label method, then the expression of PR-1, AOS, ACOI, ERF and SAM genes in wheat treated with DZSG23 at different growth stages were detected by quantitative realtime PCR. The results indicated that DZSG23 could successfully colonize wheat plant at seedling stage and surface of the spike. At the 34 d after inoculation with DZSG23 by pouring, the colonization of DZSG23 in roots, stems and leaves of wheat plants at seedling stage reached 1.437×10⁶ CFU·g^-1, 3.285×10³ CFU·g^-1 and 2.377×10³ CFU·g^-1, respectively. After 15 days of inoculation with DZSG23 strain by spraying on the surface of spikes, the surface microbial density of spike tissue still reached 7.146×10³ CFU·g^-1. Expression of defense response genes PR-1 and AOS in wheat spike treated with DZSG23 were significantly higher than those of normal control groups at different growth stages, showing DZSG23 could induce systemic response through SA-and JA-dependent signaling pathways and enhance its disease resistance.

Key words: Bacillus subtilis DZSG23, wheat, colonization, mechanism of disease resistance