Muñoz-Rojas J, Caballero-Mellado J
Programa de Ecología Molecular y Microbiana, Centro de Investigación sobre Fijación de Nitrógeno, Universidad Nacional Autónoma de México, Ap. Postal 565-A, Cuernavaca, Morelos, México.
Microb Ecol. 2003 Nov;46(4):454-64. doi: 10.1007/s00248-003-0110-3. Epub 2003 Aug 14.
Different experiments have estimated that the contribution of biological nitrogen fixation (BNF) is largely variable among sugarcane cultivars. Which bacteria are the most important in sugarcane-associated BNF is unknown. However, Gluconacetobacter diazotrophicus has been suggested as a strong candidate responsible for the BNF observed. In the present study, bacteria-free micropropagated plantlets of five sugarcane cultivars were inoculated with three G. diazotrophicus strains belonging to different genotypes. Bacterial colonization was monitored under different nitrogen fertilization levels and at different stages of plant growth. Analysis of the population dynamics of G. diazotrophicus strains in the different sugarcane varieties showed that the bacterial populations decreased drastically in relation to plant age, regardless of the nitrogen fertilization level, bacterial genotype or sugarcane cultivars. However, the persistence of the three strains was significantly longer in some cultivars (e.g., MEX 57-473) than in others (e.g., MY 55-14). In addition, some strains (e.g., PAl 5(T)) persisted for longer periods in higher numbers than other strains (e.g., PAl 3) inside plants of all the cultivars tested. Indeed, the study showed that the inoculation of G. diazotrophicus may be beneficial for sugarcane plant growth, but this response is dependent both on the G. diazotrophicus genotype and the sugarcane variety. The most positive response to inoculation was observed with the combination of strain PAl 5(T) and the variety MEX 57-473. Although the positive effect on sugarcane growth apparently occurred by mechanisms other than nitrogen fixation, the results show the importance of the sugarcane variety for the persistence of the plant-bacteria interaction, and it could explain the different rates of BNF estimated among sugarcane cultivars.
不同的实验估计，生物固氮（BNF）的贡献在甘蔗品种间差异很大。在与甘蔗相关的生物固氮中，哪些细菌最为重要尚不清楚。然而，固氮葡糖醋杆菌被认为是观察到的生物固氮的有力候选者。在本研究中，用属于不同基因型的三株固氮葡糖醋杆菌菌株接种了五个甘蔗品种的无菌微繁殖苗。在不同的氮肥水平和植物生长的不同阶段监测细菌定殖情况。对不同甘蔗品种中固氮葡糖醋杆菌菌株的种群动态分析表明，无论氮肥水平、细菌基因型或甘蔗品种如何，细菌种群数量都随植株年龄的增长而急剧下降。然而，这三株菌株在某些品种（如MEX 57-473）中的持续存在时间明显长于其他品种（如MY 55-14）。此外，在所有测试品种的植株内，一些菌株（如PAl 5(T)）比其他菌株（如PAl 3）以更高的数量持续存在更长时间。事实上，该研究表明接种固氮葡糖醋杆菌可能有利于甘蔗植株生长，但这种反应既取决于固氮葡糖醋杆菌的基因型，也取决于甘蔗品种。接种后最积极的反应出现在菌株PAl 5(T)和品种MEX 57-473的组合中。虽然对甘蔗生长的积极影响显然是通过固氮以外的机制发生的，但结果表明甘蔗品种对植物-细菌相互作用的持续存在很重要，这可以解释不同甘蔗品种间估计的生物固氮率不同的原因。
