Abstract: The Paenibacillus polymyxa strain L₁-9 of marine bacterium was labeled by antibiotic marker，and strain L₁-9^Str，rif showed the resistance to rifampicin and streptomycin at the concentrations of 160 μg/mL and 20 μg/mL，respectively. The antibacterial characters of double-resistance strain L₁-9^Str，rif and its resistance to rifampicin and streptomycin were still stable after 10 times subculturing. The pot experiment showed that L₁-9^Str，rif successfully colonized in cucumber rhizosphere soil，root tissue，stem base，cotyledon，and true leaves. The colonized dynamics of L₁-9^Str，rif in cucumber ecto-rhizosphere soil，rhizosphere and rhizoplane soil，and cucumber tissues were similar；the amount of L₁-9^Str，rif colonized in cucumber tissue was little in the early stage，but increased gradually along with the cucumber growth，and reached a peak，then decreased gradually. The amount of L₁-9^Str，rif was the most in rhizoplane soil(1.76×10⁹ CFU/g)，the followed in the rhizosphere，while the least in ecto-rhizosphere soil. The detection of L₁-9^Str，rif in cucumber tissues showed that it was the most in cotyledons(5.63×10⁴ CFU/g)，followed by its number in roots and stem bases(0 - 2 cm). The amount of bacteria in the rhizosphere soil was still in a stable level at 26 d，and the quantity from rhizoplane soil was the highest with 2.41×10⁷ CFU/g. The quantity of bacteria in the cotyledons got the highest of 4.15×10⁴ CFU/g among cucumber tissue samples. The greenhouse test showed that both strain L₁-9 and strain L₁-9^Str，rif had favorable control effects on fusarium wilt of cucumber with the control efficacy over 70% at different stages. The above results indicated that strain P. polymyxa strain L₁-9 may colonize in cucumber rhizosphere soil and tissues，and present a great potential for the bio-control of fusarium wilt of cucumber.

Key words: marine bacteria, Paenibacillus polymyxa, antibiotic marker, fusarium wilt of cucumber, colonization