Analysis of Rhizobium Haplotypes Based on Whole Genome Sequences and Relationship with Chickpea Phenotypes

Rhizobium have symbiotic interaction with legumes so they could supply nitrogen. In the first year, to characterize nitrogen fixation across evolutionary gradient in Cicer species, 18 cultivated chickpeas (C. arietinum) and 12 wild accessions (C. reticulatum, C. bijugum, C. echinospermum, C. judaicum, C. pinnatifidum and C. yamashitae) were phenotyped for fitness parameters in three treatments (control, rhizobium and nitrogen) at Patancheru, Ludhiana and Sehore in India. Cultivar chickpeas showed less nodule number / weight but more shoot weight in rhizobium treatment. Cultivated chickpea provided with improved inoculums performed equivalent to nitrogen treated plants but wild chickpea showed similar shoot weight in all three treatments. Statistical analyses suggest less symbiotic efficiency in cultivated chickpea with indigenous rhizobium which means that wild chickpea can make efficient symbiosis with indigenous rhizobium but cultivated chickpea do not. Interestingly, wild chickpeas did not utilize added nitrogen so there was no difference in nitrogen treatment. Rhizobial sequences from C. reticulatum showed the highest sequence diversity and operational taxonomic units. These results show chickpeas that have more diverse rhizobium might have high possibility to have bigger nodules and shoot. In the second year, to validate this results, 12 genotypes comprising of 6 C. arietinum (3 primitives, 3 elites), 3 accessions each of C. reticulatum and C. echinospermum were selected for undertaking field experiments to examine correlations between rhizobium genotypes and nitrogen fixation-related traits of chickpea.