1Department of Botany, Maris Stella College (Autonomous), Vijayawada-520 008, Andhra Pradesh, India.
2Department of Botany and Microbiology, Acharya Nagarjuna University, Guntur-522 510, Andhra Pradesh, India.
3Department of Botany, S.V.K.P College, Markapur, Prakasam-523 316, Andhra Pradesh, India.
4Department of Botany, J.V.R. Govt. College, Sathupally, Khammam-507 303, Telangana, India.
*Corresponding Author: T. Satyanandam, Department of Botany, Maris Stella College (Autonomous), Vijayawada-520 008, Andhra Pradesh, India, Email: t.satyanandam@gmail.com
Online Published on 02 September, 2022.
Legume nodulating bacteria (LNB), also known as rhizobia produce root nodules on leguminous plants where in nitrogen fixation takes place. In agriculture, this symbiotic relationship is significant as it provides nitrogenous fertilizers to the leguminous crops. Traditionally rhizobia were exclusively members of the Rhizobiaceae family in the Alphaproteobacteria class of bacteria. Several reports revealed that large number of diazotrophs have the ability to nodulate and fix atmospheric N2 in legumes in addition to rhizobia which are outside the Alphaproteobacteria class. Relatively less information is available on the genetic diversity of indigenous rhizobia nodulating blackgram cultivated in rice fallows. Hence the present study was carried out to know the diversity of symbiotic native nitrogen fixing bacteria isolated from the root nodules of blackgram grown in rice fallows using partial 16S rRNA sequencing.
Nitrogen fixing microsymbionts (Rhizobium strains) from root nodules of blackgram were isolated on yeast extract mannitol agar (YEMA) medium. The pure cultures were maintained at 28±2°C for 48 h. Identification of Rhizobium isolates was done by using various tests and Morphological characterization of isolates was also done by using standard microbiological methods. The PCR amplification and sequencing of 16S rRNA gene of isolates were carried out to identify the isolates.
In the present study four strains of Rhizobium designated as VM-2, VM-8, VM-9 and VM-15 were isolated. Morphologically colonies of all strains are round, transparent, entire, convex and smooth. They are Gram -ve and rod shaped. Mucilage production is noticed in VM-2, VM-8 and VM-9. The 16S rRNA gene sequences revealed that the strain VM-2 showed a close relation with Rhizobium, VM-8 and VM-9 with Bradyrhizobium where as VM-15 with Achromobater. It was concluded that the symbiotic nitrogen fixing bacteria isolated from the root nodules of blackgram cultivated in rice fallows exhibited high genetic diversity.
Achromobacter, Blackgram, Bradyrhizobium, Rhizobium, Rice fallows
