Potential Plant Growth-promoting Rhizobacteria Research Articles

Effects of two plant growth-promoting Rhizobacteria on the germination and growth of pepper seedlings (Capsicum Annum) CV. Roxy: Wirkung von zwei wachstumsfordernden Rhizobakterien auf die keimung und das wachstum von pfeffersaaten (Capsicum Annum) CV. Roxy

The effect of two plant growth-promoting rhizobacteria (PGPRs) on the germination and growth of pepper seedlings was investigated in a culture chamber. The two strains showed metabolic capacities related to their potential PGPR action. Two different patterns of inoculation were carried out. In the first, strains were inoculated when seeds were sown, and in the second when seedlings showed fully developed cotyledons. In both cases the following parameters were measured: aerial and root surface, aerial and root length and aerial and root weight. In the first pattern of inoculation no aerial parameters were modified, probably because the bacteria did not colonize the root. In the second pattern of inoculation, all parameters were significantly modified by Chryseobacterium balustinum, except root surface, which indicated that this bacterium was able to colonize the root. Serratia fonticola did not modify any parameter. In both inoculation patterns root length was reduced by both bacteria probably due to a hormonal effect. C. balustinum enhanced aerial surface, aerial length and also the dry aerial and root weight. This resulted in stronger and more robust plants with a higher adaptative capacity and a greater resistance against pathogens.

Effects of Culture Filtrates of Rhizobacteria Isolated from Wild Lupine on Germination, Growth, and Biological Nitrogen Fixation of Lupine Seedlings

In order to select potential Plant Growth Promoting Rhizobacteria (PGPRs), a selection of strains from the predominant genera in the rhizosphere of four lupine species, based on genetic divergence criteria, carried out in a previous study, yielded 11 Aureobacterium (Aur), four Cellulomonas (Cell), two Arthrobacter (Arth), two Pseudomonas (Ps), and six Bacillus (Bc) strains. Cell‐free culture filtrates of each bacterium were assayed for effects on germination, growth, and biological nitrogen fixation (BNF) of Lupinus albus L. cv. Multolupa seeds or seedlings. Four (Aur 6, Aur 9, Aur 11, and Cell 1) of the twenty‐five strains assayed promoted germination. Aureobacterium 6 and Aur 9 also increased root surface, total nitrogen content, and BNF. As a result of the screening, and considering all the variables studied, Aur 6 can be considered a plant growth promoting rhizobacterium and is suitable for further field trials in other plants and in different production systems.

Plant protection and rhizosphere colonization of barley by seed inoculated herbicide degrading Burkholderia (Pseudomonas) cepacia DBO1(pRO101) in 2,4-D contaminated soil

The 2,4-dichlorophenoxyacetic acid (2,4-D) degrading bacterium, Burkholderia cepacia (formerly Pseudomonas cepacia) DBO1(pRO101) was coated on non-sterile barley (Hordeum vulgare) seeds, which were planted in two non-sterile soils amended with varying amounts of 2,4-D herbicide. In the presence of 10 or 100 mg 2,4-D per kg soil B. cepacia DBO1(pRO101) readily colonized the root at densities up to 107 CFU per cm root. In soil without 2,4-D the bacterium showed weak root colonization. The seeds coated with B. cepacia DBO1(pRO101) were able to germinate and grow in soils containing 10 or 100 mg kg−1 2,4-D, while non-coated seeds either did not germinate or quickly withered after germination. The results suggest that colonization of the plant roots by the herbicide-degrading B. cepacia DBO1(pRO101) can protect the plant by degradation of the herbicide in the rhizosphere soil. The study shows that the ability to degrade certain pesticides should be considered, when searching for potential plant growth-promoting rhizobacteria. The role of root colonization by xenobiotic degrading bacteria is further discussed in relation to bioremediation of contaminated soils.