What is it about?
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 5T) persisted for longer periods in higher numbers tan 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 5T and the variety MEX 57-473.
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Why is it important?
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. We observed posiitive effects in the plant growth promotion in dependency of the bacterial genotype, plant variety and levels of fertilization. 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.
Perspectives
Bacterial population dynamics could explain if an interaction occurs properly and consequently the capability of bacteria to promote the growth of plants. However, there are few works showing the behavior of bacterial numbers associated to plants througth the time. It is necesary explore the population dynamics with oter bacterial species and other plants.
Ph. D. Jesús Munoz-Rojas
Benemerita Universidad Autonoma de Puebla
Read the Original
This page is a summary of: Population Dynamics of Gluconacetobacter diazotrophicus in Sugarcane Cultivars and Its Effect on Plant Growth, Microbial Ecology, December 2003, Springer Science + Business Media,
DOI: 10.1007/s00248-003-0110-3.
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