Abstract
In the pursuit of sustainable agriculture, bioinoculants usage as providers of a crop's needs is a method to limit environmental damage. In this study, a collection of cultivable putative plant growth promoting (PGP) bacteria associated with wheat crops was obtained and this bacterial sample was characterized in relation to the functional diversity of certain PGP features. The isolates were obtained through classical cultivation methods, identified by partial 16S rRNA gene sequencing and characterized for PGP traits of interest. Functional diversity characterization was performed using Categorical Principal Component Analysis (CatPCA) and Multiple Correspondence Analysis (MCA). The most abundant genera found among the 346 isolates were Pseudomonas, Burkholderia, and Enterobacter. Occurrence of PGP traits was affected by genus, niche, and sampling site. A large number of genera grouped together with the ability to produce indolic compounds; phosphate solubilization and siderophores production formed a second group related to fewer genera, in which the genus Burkholderia has a great importance. The results obtained may help future studies aiming prospection of putative plant growth promoting bacteria regarding the desired organism and PGP trait.
Highlights
Since the description of the association of non-symbiotic diazotrophic bacteria with non-legume plants (Baldani et al, 1983), free-living bacteria have demonstrated positive effects in promoting plant growth, proving their agronomic potential through biological nitrogen fixation (e.g., James et al, 2002; Ambrosini et al, 2012)
Despite the fact that all sampling sites analyzed were traditionally used to crop wheat and that all sampled plants were at the same stage of maturity, Principal Coordinate Analysis (PCA) was able to separate the regions into distinct groups according to their soil characteristics and diversity indices
Little information is available about the specific effects of parameters such as organic carbon and total nitrogen content of the soil on microbial diversity, information such as organic carbon and total nitrogen content could affect the diversity of soil bacteria, including nitrogen-fixing bacteria (Ramette and Tiedje, 2007)
Summary
Since the description of the association of non-symbiotic diazotrophic bacteria with non-legume plants (Baldani et al, 1983), free-living bacteria have demonstrated positive effects in promoting plant growth, proving their agronomic potential through biological nitrogen fixation (e.g., James et al, 2002; Ambrosini et al, 2012). These organisms present in the rhizosphere, root surfaces or inside plant tissues are able to directly or indirectly induce plant growth, as well as resistance to or protection against pathogens (Lugtenberg and Kamilova, 2009). At the right set of conditions, a targeted effect on the behavior of a certain microbial subpopulation, e.g. an introduced inoculum, which is supposed to get established and interactive with the plant root, is possible (Hartmann et al, 2009)
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