青枯菌无致病力菌株FJAT-1458与强致病力株FJAT-91的竞争生长作用

为了明确青枯菌无致病力菌株FJAT-1458的生防竞争机制，本研究采用体外共培养方法研究了碳源、氮源和培养时间对菌株FJAT-1458和青枯菌强致病力菌株FJAT-91竞争生长的影响；同时，研究了菌株FJAT-1458和FJAT-91在番茄植株体内的竞争生长。结果表明，碳源含量低于20%时，菌株FJAT-1458不能生长，而菌株FJAT-91可生长；无氮源条件下，FJAT-1458和FJAT-91均不能生长；碳源和氮源含量达100%时，FJAT-1458的菌体浓度（2.16×10⁹ cfu/mL）显著低于FJAT-91的菌体浓度（3.24×10⁹ cfu/mL）。混合培养24 h前，FJAT-1458生长量大于FJAT-91，24 h后则相反。在单独接种或混合接种5 d后，FJAT-1458和FJAT-91均在番茄植株体内出现最大定殖量，随后迅速减少；FJAT-91在单独接种15 d时，定殖数量为0；两种菌株单独接种的定殖数量均大于混合接种（接种15 d除外）。先接种FJAT-1458，3 d后接种FJAT-91对番茄青枯病的防效（100%）显著高于同时接种FJAT-1458和FJAT-91（74.67%）。本研究表明，在体外无致病力菌株FJAT-1458对碳源和氮源的营养竞争能力弱于强致病力菌株FJAT-91；在体内无致病力菌株FJAT-1458会抑制强致病力菌株FJAT-91的生长；因此，FJAT-1458的生防竞争机制中，营养竞争起非主导作用，而位点竞争可能是主导因素。

Competitive Growth of Ralstonial solanacearum Avirulent Strain FJAT-1458 and Virulent Strain FJAT-91

The aim of this study is to determine the biocontrol competition mechanism of Ralstonia solanacearum avirulent strain FJAT-1458. Effects of carbon source, nitrogen source and culture time on the competitive growth between avirulent strain FJAT-1458 and virulent strain FJAT-91 were analyzed by co-culture in vitro. Furthermore, the competitive growth between FJAT-1458 and FJAT-91 was also in the tomato plant. The results showed that the virulent strain FJAT-91 could grow but the avirulent strain FJAT-1458 could not, when they were co-cultured in the media with content of carbon source less than 20%. Both strains could not reproduce when there was no nitrogen source. The cell concentration of FJAT-1458 (2.16×10⁹ cfu/mL) was significantly less than FJAT-91 (3.24×10⁹ cfu/mL) when the contents of carbon source and nitrogen source content were 100%. The growth of avirulent strain FJAT-1458 was faster than the virulent strain FJAT-91 before 24 h, but became slower after 24 h. The colonization number of FJAT-1458 and FJAT-91 reached the highest 5 d after sole inoculation or co-inoculation, and then quickly decreased. Moreover, the colonization number of FJAT-91 was 0 15 d after sole inoculation. The colonization number of both FJAT-1458 and FJAT-91 by sole inoculation was higher than that by co-inoculation (except for 15 d). The pre-inoculation of FJAT-1458 for 3 d had higher control efficiency (100%) than co-inoculation of FJAT-1458 and FJAT-91 at the same time (74.67%). It was concluded that the utilization abilities of carbon and nitrogen source for FJAT-1458 were poorer than those for FJAT-91 when co-cultured in vitro, but FJAT-1458 could restrained by the growth of FJAT-91 when co-inoculation in tomato plants. In the biocontrol competition mechanism of strain FJAT-1458, site competition may be the dominant factor, but not nutrient competition.