Rhizosphere Microbial Communities: Isolation, Characterization, and Value Addition for Substrate Development

Abstract

Rhizosphere, the soil region nearest to plant root system, inhabits various microorganisms varying in their community structure and diversity, still remains largely unexploited despite so much of breakthroughs in isolation and characterization, but lacks in addressing citrus speci fi c rhizosphere properties. Exploiting microbial synergisms is one of the popular methods of substrate dynamics and associated changes in nutrient environment of rhizosphere. Soil microbial biomass dominates fungal mycelium accumulates and retains mineral nutrients, immobilizing as much as ~20% of the total soil N and P. The extraradical mycorrhizal mycelial (attains as much as 3% of root weight) networks are recognized as the hidden nutrient/ water-absorbing interfaces (glomalin, a soil-based glycoprotein secreted by AMF as a major seat of activity) in addition to safeguarding citrus against a number of other biotic and abiotic stresses. The microbial diversity existing within top 0-20-cm citrus rhizosphere soil was characterized and isolated by the promising microbes, namely, Bacillus polymyxa , Azoto bacter chroococcum , Bacillus mycoides , Pseudomonas fl uorescens , and Trichoderma harzianum . Pure culture of these microbes in value-added form ( Bacillus polymyxa 33-44 × 10 6 -10 7 cfu mL −1

Temporal Dynamics of Rhizobacteria Found in Pequin Pepper, Soybean, and Orange Trees Growing in a Semi-arid Ecosystem

“…and Klebsiella spp., known to improve drought stress (Marasco et al, 2012). For orange trees, Bacillus was the most abundant genus at this time, whereas Bacillus has generally been reported as a dominant genus of the endophytic communities in Citrus (Wu and Srivastava, 2012). In the case of soybean, sampling times corresponded to plant developmental stages (i.e., vegetative, flowering and fruiting, and senescent).…”

Effects of Bacterial and Fungal Inocula on Biomass, Ecophysiology, and Uptake of Metals of Alyssoides utriculata (L.) Medik.

“…The bacterial and fungal mix used ( P. fluorescens and P. ochrochloron ) improved the aboveground biomass, as similarly documented for different microbial consortia used in crops, in Citrus sp. [ 36 , 51 , 52 , 53 ], and in the hyperaccumulator Miscanthus × giganteus (Mxg) J.M.Greef, Deuter ex Hodk., Renvoize [ 54 ]. Nevertheless, the documented consortia showed a lower increase in biomass (up to 3.1-fold) compared to our results.…”

Quantifying Crop Rhizosphere Microbiome Ecology: The Next Frontier in Enhancing the Commercial Utility of Agricultural Microbes

“… 21 , 22 For example, the ability to culture members of the rhizosphere microbiome from citrus was shown, and known plant growth promoting organisms were isolated, including Bacillus polymyxa, Azotobacter chroococcum, Bacillus mycoides, Pseudomonas fluorescens , and Trichoderma harzianum . 23 In citrus greening disease, or huanglongbing (HLB), the pathogen Candidatus liberibacter spp., was shown to decrease the abundance of these beneficial members of the plant microbiome. 22 , 24 , 25 Blaustein et al also analyzed the leaf microbiome and showed that the Candidatus liberibacter spp.…”