Bioprospecting in potato fields in the Central Andean Highlands: screening of rhizobacteria for plant growth-promoting properties.

The Central Andean Highlands are the center of origin of the potato plant (Solanum tuberosum). Ages of mutualism between potato plants and soil bacteria in this region support the hypothesis that Andean soils harbor interesting plant growth-promoting (PGP) bacteria. Therefore, the aim of this study was to isolate rhizobacteria from Andean ecosystems, and to identify those with PGP properties. A total of 585 bacterial isolates were obtained from eight potato fields in the Andes and they were screened for suppression of Phytophthora infestans and Rhizoctonia solani. Antagonistic mechanisms were determined and antagonistic isolates were further tested for phosphate solubilization, 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity, and production of NH3- and indole-3-acetic acid (IAA). PGP was studied in healthy and R. solani diseased plantlets under growth room conditions. Performance was compared to the commercial strain B. subtilis FZB24(®) WG. Isolates were dereplicated with matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS), and identified with 16S rRNA gene sequencing and multi locus sequence analysis (MLSA). A total of 10% of the isolates were effective antagonists, of which many were able to solubilize phosphate, and produce IAA, ACC deaminase, NH3 and hydrogen cyanide (HCN). During growth room experiments, 23 antagonistic isolates were associated with plant growth-promotion and/or disease suppression. Ten isolates had a statistically significant impact on test parameters compared to the uninoculated control. Three isolates significantly promoted plant growth in healthy plantlets compared to the commercial strain, and seven isolates outperformed the commercial strain in in vitro R. solani diseased plantlets.

Ghyselinck J ，Velivelli SL ，Heylen K ，O'Herlihy E ，Franco J ，Rojas M ，De Vos P ，Prestwich BD ... -  《-》

Effectiveness of multi-trait Burkholderia contaminans KNU17BI1 in growth promotion and management of banded leaf and sheath blight in maize seedling.

Plant growth promoting (PGP) bacteria enhance plant growth and are a green alternative to chemical fertilizers. In our study, an effective plant growth promoting rhizobacteria (PGPR) strain, KNU17BI1, was isolated from rhizospheric soil of maize, South Korea. The strain was tested in vitro for specific PGP and antifungal traits, such as phosphate solubilization, zinc solubilization, indole acetic acid (IAA) production, ammonia production, nitrogen fixation, 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity, siderophore hydrogen cyanide production (HCN) and hydrolytic enzyme activity. Furthermore, in viro antifungal activity was done in a laboratory and in vivo effect of KNU17BI1 on banded leaf and sheath blight intensity as well as plant growth promotion on maize seedling were conducted under greenhouse conditions. The strain was found to be highly effective toward all the parameters except HCN production. The strain KNU17BI1 was identified on the basis of 16S RNA and multilocus sequence analysis (MLSA) and confirmed as Burkholderia contaminans. This study for the first time demonstrated potent in vitro antifungal activity of B. contaminans against Rhizoctonia solani AG-1(IA), Pythium graminicola, Fusarium moniliforme, Alternaria alternata, Alternaria solani, Fusarium graminearum, Stemphylium botryosum Wallr, Colletotrichum dematium, Stemphylium lycopersici and Fusarium oxysporum f.sp. melonis. Furthermore, in this study, for the first time, the potential of B. contaminans stain KNU17BI1 in controlling banded leaf and sheath blight of maize caused by R. solani AG-1(IA) was reported. Therefore, further studies are warranted on the structural identification of actual compounds behind such activities that would be exploited further for biocontrol as well as plant growth promotion.

Tagele SB ，Kim SW ，Lee HG ，Kim HS ，Lee YS ... -  《-》

Endophytic bacterial communities of field-grown potato plants and their plant-growth-promoting and antagonistic abilities.

Sessitsch A ，Reiter B ，Berg G 《CANADIAN JOURNAL OF MICROBIOLOGY》

Screening of PGPR from saline desert of Kutch: growth promotion in Arachis hypogea by Bacillus licheniformis A2.

Rhizosphere of a halotolerant plant Suaeda fruticosa from saline desert of Little Rann of Kutch, Gujarat (India) was explored for isolation of PGPR form the rare ecological niche having4.33% salinity. Total 85 isolates from the rhizosphere belonging to different species were isolated. Out of 85 isolates, 23 could solubilize phosphate and 11 isolates produced IAA. Seven isolates showed both the traits of phosphate solubilization and IAA production. All isolates which showed either of IAA production or phosphate solubilization or both were further screened for other PGP traits like production of ammonia, siderophore, chitinase, HCN and assessment of their antifungal activity. Out of all the screened isolates, Bacillus licheniformis strain A2 showed most prominent PGP traits in vitro and it was tested in vivo for growth promotion of Groundnut (Arachis hypogaea) under saline soil condition. In presence of soil supplemented with 50 mM NaCl, B. licheniformis treated plants showed increase in fresh biomass, total length and root length by 28%, 24% and 17% and in absence of NaCl it was 43%, 31% and 39% respectively.

Goswami D ，Dhandhukia P ，Patel P ，Thakker JN ... -  《-》

Bacillus strains isolated from rhizosphere showed plant growth promoting and antagonistic activity against phytopathogens.

Seven bacterial isolates screened from rhizosphere of common bean growing at Uttarakhand Himalaya showed potential plant growth promoting (PGP) and antagonistic activities. Based on 16S rRNA gene sequence the isolate BPR7 was identified as Bacillus sp. BPR7. The strain BPR7 produced IAA, siderophore, phytase, organic acid, ACC deaminase, cyanogens, lytic enzymes, oxalate oxidase, and solubilized various sources of organic and inorganic phosphates as well as potassium and zinc. Strain BPR7 strongly inhibited the growth of several phytopathogens such as Macrophomina phaseolina, Fusarium oxysporum, F. solani, Sclerotinia sclerotiorum, Rhizoctonia solani and Colletotricum sp. in vitro. Cell-free culture filtrate of strain BPR7 also caused colony growth inhibition of all test pathogens. PGP and antifungal activities of Bacillus sp. BPR7 suggest that it may be exploited as a potential bioinoculant agent for P. vulgaris.

Kumar P ，Dubey RC ，Maheshwari DK 《-》