Isolation and characterization of rhizobium strains from root nodules of faba bean (Vicia faba L.)

Isolation and identification of Rhizobium bacteria from Faba bean (Vicia faba L.) roots grown in gypsiferous soil and testing their efficiency in production growth regulate(IAA) and siderophorses

“…Table 8 shows some biochemical tests for bacteria isolated from the root nodules of Faba bean plants, It was found that most of the isolates gave colors from pink, light pink and white when grown on the medium of the Congo red stain with a concentration of 0.025% according to its ability to absorb the stain, as it gave 5 isolates the pink color, while the rest of the isolates gave light pink and white color, and the reason for this is due to the low ability of the root nodule bacteria to absorb the stain which indicates the purity of the studied isolates, while other bacteria are colored in red, the same table shows the results of the 0.5% bromothymol blue stain test, which indicates the bacteria that are able to change the color of the medium from green to yellow, belonging to the fastgrowing species such as Rhizobium, and the bacteria that change the color of the medium to blue belong to the slow-growing species such as the genus Bradyrhizobium., most of the isolates of the study gave yellow color for their production of compounds that increase the acidity of the medium after growing on this medium, while the isolates (R7, R16, R18, R19, R20, R21, R22) gave the blue color, which indicates their production of compounds that increase the basicity of the medium, and converge with the results Yesmin et al (2021) in their study on Rhizobium bacteria isolated from the root nodules of Faba bean plants, and indicated that the bacterial isolates have the ability to produce compounds that increase the acidity of the medium and belonging to the fast-growing species after growing on this medium, The same table shows the results of the Hofer alkaline test, which shows that all bacterial isolates gave a negative result of the test, and this indicates their inability to grow at high levels of pH, which distinguishes them from other bacterial genera such as Agrobacterium, which have the ability to grow at these levels, and from the keto-Lactose test, all isolates gave a positive result except for two isolates that gave a negative result for the test, and this converges with Al-Samarrai (2017) when studying the root nodule bacteria isolated from several leguminous plants. Table 8 indicates that 20 isolates have the ability to hydrolysis hydrogen peroxide into oxygen and water, while 3 isolates gave a negative result for the test.…”

Isolation and Diagnosis of the Root Nodule Bacteria Associated with Mung Bean Plant in Gypsiferous Soil and Testing the Promotional Criterion of Isolates

“…Table 5 shows the variability of isolates based on their ability to absorb the Congo red dye, where eight isolates appeared as light pink and two as pink, This result is consistent with [1] in their study on Bradyrhizobium vignae bacteria isolated from the roots of the cowpea plant. Most isolates changed the color of the medium from green to yellow when grown on a medium containing bromothymol blue, indicating that they produce compounds that increase the acidity of the medium, and these belong to fast-growing groups (Rhizobium) except for one isolate (M6) that changed the color of the medium to blue, indicating that it produces compounds that increase the alkalinity of the medium, and these belong to slow-growing groups (Bradyrhizobium), This is consistent with [27] in their study on Rhizobium bacteria isolated from the root nodules of Faba Bean. All isolates gave a positive result for the catalase test, indicating their ability to break down hydrogen peroxide, leading to the release of oxygen bubbles, which is consistent with [28], in their study on Rhizobium bacteria isolated from the roots of nine legume plant species.…”