Characterization of intrinsic variability of Mesorhizobium ciceri isolates of cultivated fields.

A large number of putative rhizobial isolates were obtained from the root nodules of various chickpea cultivars growing in agricultural research fields. Of these, thirty were selected and characterized for traits, such as, generation time, intrinsic azide resistance and several symbiotic characters.

Lipochitooligosaccharides and legume Rhizobium symbiosis--a new concept.

Legume-Rhizobium symbiosis is a multistep process characterized by the formation of root nodules on the host plant. A number of genes from both symbiotic partners share information during the interaction process. Nodulation genes (nod, nol and noe) have been classified as common nodulation genes and host specific (hsn) nodulation genes. Though common nodulation genes are enough to form root nodules, host specific nodulation genes are needed for specific interaction leading to formation of functional nodules. Core lipochitooligosaccharides (LCOs), the products of common nodulation genes are modified by the action of host specific nodulation genes. LCOs seem to be present in legumes as well as nonlegume and are known to act as a morphogen by acting as auxin-transport inhibitor. The understanding of Nod factor may contribute to reveal complex biological functions such as developmental regulation, signal transduction and plant morphogenesis.

Construction of a gene bank of Rhizobium leguminosarum Rld 164.

The total genomic DNA of R. leguminosarum Rld164 (trp, sms, azi) was cloned in the EcoR1 site of the wide host and conjugally transferable cosmid vector pLAFR1. The average insert size in the gene clones of the bank was found to be 21.3 Kb. The strain R. leguminosarum Rld7 (leu-1) was employed as recepient to conjugally transfer and thus isolate the complementary leu+ allele carrying clones from the gene bank.