At the Center our group is engaged in developing efficient nitrogen fixing and those with improved nodule occupancy strains of Mesorhizobium ciceri . The approach we are adopting is to isolate mutants of biological nitrogen fixation process and then identify the relevant genes and manipulate these to develop efficient strains.

(A) The TEM studies of the dct mutant induced nodules have been carried out and relevant aberrations of the nodule development have been identified. The ineffectiveness of the mutant strains was supported by the following facts: i) starch accumulated in the host cortical cells remains unutilized, where as in the wild type strain starch produced is being utilized simultaneously during nitrogen fixation phase of the cells and ii) presence of senescent bacteroid Fig. 1A, B.

Fig.1. Electron microscopic sections of nodules elicited by the Mesorhizobium ciceri strain TAL620 and its dct- mutant. A, TAL620 (Wild type); B, SD3. Starch grains (s), amyloplast (am), scnescent bacteroid (sb), endoplasmic reticulum (er), gas exchange vesicle (vs), mitochondria (mt), bacteriod (b).

Isolation of genotype specific Mesorhizobium ciceri from root nodules of chickpea varieties

Legume rhizobium symbiosis is a very specific interaction and genes present both on legumes and rhizobia contribute to this process. Any genetic alteration either in rhizobia or legumes lead to loss of this interaction. Considering this specificity in symbiotic interaction and the facts that every year new and new genotypes in legumes are introduced for cultivation, a desirable matching change in rhizobia has not been thought about. This aspect seems to be missing at present in developing biofertilizer strains in rhizobia. A programme has been inititated at the Center to examine this aspect and suggest development of rhizobia matching to popular cultivars of a location. In following such a practices the most serious problem of competition faced by inoculant strains will be reduced/eliminated.

Contact:- Dr. L.R. Kashyap (lrkashyap@hotmail.com)