Assessment of diversity and plant growth promoting attributes of rhizobia isolated from Cajanus cajan L.

Abstract

Eight (8) strains of rhizobia from Pigeon pea (Cajanus cajan) were isolated and identified based on their physiological and biochemical characteristics using standard methods. Five (5) of the isolates (KCC1 to
KCC5) were subjected to partial 16S rDNA gene sequencing for phylogenetic analysis. Genetic diversity was investigated using restriction patterns produced by amplified rDNA restriction analysis (ARDRA) and were placed into different clusters. They were identified as Ensifer sinorhizobium hence named as Ensifer spp. KCC1 to KCC4. KCC5 is placed in Ensifer fredii clade. Nodulation and nitrogen fixing abilities of the isolates were confirmed by amplification of nodC and nifH genes. All of them showed indole-3-acetic acid production and phosphate solubilization activity. Only two isolates (KCC2 and KCC5) produced siderophore on CAS medium and showed strong antagonistic effect against Fusarium udum. None of the isolates produced cyanogen. The study showed that there is a considerable homogeneity amongst C. cajan root nodule isolates and can be exploited for plant growth promotion of C. cajan with effective antagonism against F. udum.

Keywords: Diversity, Ensifer (Sinorhizobium) spp., pigeon pea (Cajanus cajan)