Study on factors influencing the siderophore production ofBacillus subtilis Bs-15 and effects of Bs-15 on diseasecontrol and growth promotion of sweet pepper

The influence of culture conditions on the siderophore production of Bacillus subtilis Bs-15 was studied.The results showed that Bs-15 could yield high content of siderophore when inoculated 100 mL modified MM medium (pH 7.2) with glucose as carbon source and tryptophan as nitrogen source,and shaking under 200 r/min in 250 mL flask at 37℃.The effects of B.subtilis Bs-15 on the biocontrol of Fusarium wilt and growth promotion of sweet pepper was studied by pot experiment.The results showed that Bs-15 decreased the incidence of Fusarium wilt significantly,with the control efficacy of 44.4% when inoculated B.subtilis Bs-15 and Fusarium oxysporum Schl.f.sp. simultaneously,and of 56.94% when inoculated F.oxysporum Schl.f.sp.2 days after treatment of B.subtilis Bs-15;However,iron significantly reduced the suppression effect of Bs-15 on Fusarium wilt of sweet pepper,with control efficacy of 12.5% and 23.4% ,respectively.There were significantly differences between Bs-15 treatment and control in plant height after treatment for 14,21,28 and 40 days,which increased from 27.24% to 54.53%.B.subtilis Bs-15 could shorten the days of 50 percent flowering of sweet pepper by 17.26 days,and enhance the average fruit weight and yield per plant of sweet pepper by 36.92% and 49.68%,respectively.The results indicated that B.subtilis Bs-15 had good effects on the Fusarium wilt and growth promotion of sweet pepper.