Characterization of Rhizobia Isolated from Tigray Soil and Assessment of Their Effect on Germination and Seedling Vigor of Wheat and Field Pea
Table 1
Confirmatory tests used to identify Rhizobia isolates.
Confirmatory tests
Summary of the procedures
References
Bromothymol blue test
Fresh rhizobia isolates were streaked on yeast mannitol agar medium containing 5 ml of 0.5% bromothymol blue. After incubation, the yellow color indicated fast-growing rhizobia that produce acid, while the blue color indicated slow-growing rhizobia that produce alkaline
Yeast mannitol agar was prepared by adding 0.0025% (w/v) Congo red powder. A 24-hour-old rhizobial culture was then spot inoculated on the medium and incubated at 28 ± 2°C for 48 hours. After the incubation period, the coloration of the bacterial colony was observed and recorded
A glucose peptone agar medium was prepared with the following ingredients: glucose at 10 g/L, peptone at 20 g/L, NaCI at 5 g/L, and agar at 15 g/L. Bacterial cultures were then introduced onto plates containing this agar medium and incubated at a temperature of 28 ± 2°C. After 72 hours of incubation, the growth response of the bacteria was examined
Rhizobia isolates were streaked on plates containing the yeast mannitol agar medium with a high pH of 11.0. The pH of the medium was adjusted using 1N NaOH. A yeast mannitol agar plate with a normal pH of 6.8 was used as a control. The plates were then incubated for 48 hours at a temperature of 28 ± 2°C, and the growth of the isolates was observed
The freshly prepared bacterial culture was spot-inoculated onto a lactose agar medium and incubated for 4 days at a temperature of 28 ± 2°C. After the incubation period, Benedict’s reagent (5 ml) was added carefully to the petri-plates containing the bacterial culture. The mixture was then incubated at room temperature for an hour. The appearance of a yellow zone around the colony indicates contamination
