Diversity and Phytobeneficial Properties of Indigenous Root Nodule Bacteria and Arbuscular Mycorrhizal Fungi Associated with Erythrina Species and their Effect on Growth of the Host Plant under Greenhouse Conditions

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Addis Ababa University


Erythrina is a leguminous tree used in agro-forestry practices in the southern and southwestern Ethiopia. The legume-rhizobium symbiosis provides N to plants, while Legume-AMF symbiosis enhances P availability. Despite the crucial agro-forestry attributes, there were scarcities of information on species diversity of arbuscular mycorrhizal fungi (AMF) associated to E. brucei, genetic and functional diversity, and eco-physiological stress tolerance traits of bacteria isolated from the root nodules of E. abyssinica. The objectives of this study were to; 1) determine AMF species diversity and richness associated with Erythina brucei; 2) the genetic and functional diversity and eco-physiological stress tolerance traits of bacteria isolated from the root nodules of E.abyssinica ;3) evaluate inorganic phosphate solubilizing efficiency and multiple phytobeneficial properties of root nodule bacteria associated with E. abyssinica; 4) evaluate the symbiotic effectiveness of Bradyrhizobium species, and evaluate the effects of multiple inoculation of the consortia of microorganisms on Erythrina abyssinica growth, nodulation, and shoot TN and P contents in greenhouse condition. Soil samples were collected from different E.spp growing areas involved various land use types and trap cultures were established. AMF spore extraction and species identification was done from soils obtained from the rhizosphere of E. brucei. The root nodule bacteria of E. abyssinica were obtained by plant infection method. The genetic diversities were studied using Amplified ribosomal DNA restriction analysis (ARDRA). The nifH was gene screened and the taxonomic position was determined using 16S rRNA sequence analysis. Plant growth promoting traits were also evaluated and selected microbial inputs were studied for their effects on E. abyssinica growth, nodulation, nitrogen fixation and uptake P in the greenhouse condition. Eleven AMF genera and 33 species were recovered. The ARDRA grouped the bacterial isolates in to twelve clusters at 70 % similarity level. NifH gene was amplified in 15 (50%) of the root nodule bacteria the 16S rRNA sequence analysis grouped the bacterial in to nine genera (species): Bradyrhizobium (n=3), Paenibacillus (n=2), Bacillus (n=2), Staphylococcus (n=2), Enterobacter (n=2), Achromobacter (n=1), Acinetobacter (n=3), Gluconobacter (n=4) and Stenotrophomonas (n=2). Achrmobacter, Acinetobacter, Bacillus, Gluconobacter, Paenibacillus, Staphylococcus and Stenotrophomonas are the first reports from E. brucei root nodules. In addition, Bradyrhizobium cajani and Bradyrhizobium cytisi are the first reports from E. abyssinica root nodules and from Ethiopia as well. The 61.9%, 76.2%, 47.6%, 33.3% and 19.04% of the isolates were inorganic phosphate solubilizers, IAA, NH3, HCN and chitinase producers respectively. The maximium shoot length and dry weight improvements (140%) and (267%) were recorded by multiple inoculations involved B. shewense (AU27) + Glomus sp.1(AMF1) + Acaulospora sp.1 (AMF2) + A. soli (AU4). Similarily, the maximum shoot total nitrogen improvement (260%) was recorded in treatment received B. shewense (AU27) + A. soli (AU4) inoculation; whereas the highest shoot P improvement (1200%) was recorded by B. shewense (AU27) + Glomus sp.1 (AMF1) inoculation. AMF species richness was affected by land use types and geographic locations. Phylogenetically and functionally diverse bacteria were inhabited in the root nodules of E. brucei. Multiple inoculations enhanced E. abyssinica growth and development, biomass production, nitrogen fixation and multiple inoculations also improved phosphorus uptake by the host plant. Synergistic interaction was observed among the microsymbionts and macrosymbiont. More studies are required to explore the rhizosphere of E. abyssinica and the performance of the microbial inputs which exhibited potential performance in greenhouse needs evaluation in the field condition.



E. Brucei, Inoculation, Bradyrhizobium, ARDRA, Genetic Diversity, Nifh, AMF, E.abyssinica