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The impact produced by agrochemicals on periurban agriculture soils generates an environmental concern. The objective of this work was to evaluate the potential of native plant growth-promoting bacteria to recover the horticultural soil quality for bioinoculant design using Eisenia andrei as bioindicator. Total phosphorus determination and bioassays with E. andrei cholinesterases, carboxylesterases and glutathione S-transferases as biomarkers were performed. Glutathione S-transferase levels were significantly augmented (~ 30%) evidencing the risk of uncontrolled use of agrochemicals. Native Pseudomonas migulae S1-2, Sphingobium yanoikuyae SP-3 and Leucobacter aridicollis RP-7 exhibited plant growth-promoting properties. Indole-3-acetic acid production of 14.0 ± 0.1, 69 ± 1 and 6.4 ± 0.1 µg mL−1 and phosphorus solubilisation of 46, 133 and 158 mg P L−1 were obtained from culture supernatants. Bacterial supernatants increased the root elongation of Lactuca sativa seeds up to 10%. These selected bacteria demonstrated their potential to design a biofertiliser formulation to restore deteriorated horticultural soils. [ABSTRACT FROM AUTHOR]

Plant growth promoting rhizobacteria (PGPR) are strains of naturally occurring soil bacteria that live in close vicinity to the plant's rhizosphere region which possess the capability to augment host growth. This study was conducted to isolate and identify potential PGPR isolates indigenous to Metroxylon sagu, Rottb. rhizosphere. These potential isolates were characterised based on their beneficial plant growth promoting (PGP) properties and identified by molecular analysis via 16S rDNA sequencing. A total of 18 isolates were successfully isolated, out of which five isolates were tested, and designated as (S1A, S2B, S3A, S3C and S42). Among the five isolates, two isolates (S2B and S3C) were found to produce high levels of indole-3-acetic acid (2.96 µg/mL and 10.31 μg/mL), able to fix nitrogen and show significant activity in phosphate solubilisation. The analysis of their sequences via National Center for Biotechnology Information (NCBI) suggested their close identity towards Lysinibacillus sphaericus and Bacillus thuringiensis. It can be concluded that the isolated PGPR possesses beneficial PGP attributes. It can be implied that the isolated PGPR are potential to be used as inoculant biofertilisers, beneficial for Metroxylon sagu, Rottb. growth. Hence, further studies need to be done to evaluate the effectiveness of the beneficial microbes towards sago seedlings growth, under pot experiment. [ABSTRACT FROM AUTHOR]

In the present study, we reported the isolation and molecular characterisation of 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase-producing endophyte and its effect on alleviating drought stress in maize. Ten morphologically distinct indigenous plant growth-promoting rhizobacteria (PGPR) from maize roots and rhizosphere were screened for multiple plant growth-promoting (PGP) traits, and of ten, two strains (DHK and B1N1) possessing maximum PGP traits were evaluated at three water stress regimes in maize: (i) 80% field capacity (FC), (ii) 60% FC, and (iii) 40% FC for 45 days, starting 15 days after sowing to the maturity. Inoculation of DHK strain with maize at 80% FC induced a significant increase in plant biomass (root biomass, 86.67%; shoot biomass, 111.63%) together with decreased reactive oxygen species and increased activity of antioxidant enzymes (superoxide dismutase, 14.11 U/g fresh weight; peroxidase, 1.14 U/g fresh weight and catalase; 14.91 U/g fresh weight) compared to uninoculated control at same water regime (80% FC). The derivative strain also significantly accrued nutrients in maize and enhanced total chlorophyll and amino acid content in comparison with non-inoculated plants. 16S rDNA analysis of DHK strain revealed its lineage to Bacillus subtilis. Present investigations demonstrated the potential of the bacterial partner in alleviating drought stress in maize. [ABSTRACT FROM AUTHOR]

Arbuscular mycorrhizal (AM) fungi and plant growth-promoting rhizobacteria, responsible for enhancing plant nutrition, vigour and growth, may be used to reduce dosages of chemical fertilisers. Technologies that allow an economically viable and efficient application of these beneficial microbes in large scale agriculture must be studied. Seed coating is a potential delivery system for efficiently introducing minor amounts of bioinoculants. Despite the dramatic reduction on inoculum dose per plant, inoculation of AM fungi via seed coating was as effective as conventional soil inoculation. Fertilisation and inoculation had a significant impact on maize shoots nutrient concentrations. Different fertilisation regimes did not influence mycorrhizal colonisation. Plants without fertilisation and singly inoculated with R. irregularis showed shoot nutrient concentration increments of 110, 93, 88 and 175% for nitrogen, phosphorus, potassium and zinc, respectively, comparing with non-inoculated controls. Plants singly inoculated with P. fluorescens via seed coating under full fertilisation, presented enhancements of 100, 75 and 141% for magnesium, zinc and manganese, respectively, comparing with non-inoculated controls. Seed coating is a promising tool for delivering microbial inoculants into the soil, while promoting sustainable production of maize. This technology is particularly pertinent in low input agriculture, with potential environmental profits and food quality improvements. [ABSTRACT FROM AUTHOR]

ABSTRACT Maize, Zea mays is the most important grain crop in South Africa and is a staple food in many African countries. The beneficial effects of plant growth-promoting rhizobacteria on crop growth and yield have been well documented, but obtaining reproducible results under field conditions is often difficult. In the current study, five selected rhizobacterial strains that showed plant growth-promoting activities in pilot studies were evaluated for potential enhancement of maize yield under field conditions. The five strains together with a commercial standard were assessed as seed treatments of maize over three seasons in four different soil types. The strains were identified on the basis of 16S rRNA sequencing as Lysinibacillus sphaericus ( T19), Paenibacillus alvei ( T29), Bacillus safensis ( S7) Bacillus pumilus ( A26) and Brevundimonas vesicularis ( A40). The best yield increases in maize were obtained during the 2011/2012 and 2012/2013 seasons in the Shortlands ecotope with the rhizobacterial strains T19, T29 and S7, resulting in yield increases ranging from 24% to 34%. Strain T19 rendered the most consistent yield increases during the three successive field trials amounting to 33% and 24% in Shortlands ecotope and 12% in Clovalley ecotope, respectively. During 2013/2014 a consortium of three strains, viz. T19, S7 and A26 gave a 32% yield increase in Clovalley ecotope. All the rhizobacterial strains solubilised phosphate in vitro except T19. Strain T29 showed the best nitrogen-fixing activity in vitro, proliferating on a nitrogen-free substrate and also producing ammonia. All the strains tested positive for indole acetic acid production. The current study demonstrates the ability of rhizobacterial strains T19, T29, S7 and A26 applied as seed treatments to significantly enhance maize yield in the field, making development and commercialisation of these strains a viable option. [ABSTRACT FROM AUTHOR]

One of the major issues facing humankind is global food security. A changing climate, coupled with a heightened consumer awareness of how food is produced and legislative changes governing the usage of agrichemicals for improving plant health and yield, means that alternative, more integrated and sustainable approaches are needed for crop management practices. To this end, there is increasing recognition of the value of the role of microbial inoculants in agriculture. The focus of this review is to understand how plant-growth-promoting bacteria and arbuscular mycorrhizal fungi can play a part in improving crop yield by promoting the health status of the plant through the sequestration of various nutrients and in the control of plant diseases. [ABSTRACT FROM AUTHOR]