Sasikumar NairPadmanabhan Nair, VKAU2020-07-252020-07-251989http://krishikosh.egranth.ac.in/handle/1/5810149842PGThe present investigation on varietal variation for nodulation by Rhizobium in greengram was conducted at College of Agriculture, Vellayani, Trivandrum. The field trial for host varietal specificity was done at C. S. R. C Karamana of Kerala Agricultural University and in a farmer's plot at Pattom, Trivandrum. Rhizobium capable of nodulation in greengram was isolated from 10 out of 14 different soil samples collected from Alleppey, Quilon and Trivandrum Districts. The ten isolates of Rhizobium obtained initially were screened for their nodulation efficiency under aseptic pot culture conditions by using the greengram variety C0-3. In this screening it was found that the increase was maximum in R5 treatment where 188.30 nodules were formed per plant when compared to only 8.33 in the uninoculated control. The fresh and dry weights of nodules formed 455 and 119.33 mg respectively were also maximum in the R5 treatment. A significant increase in root length was obtained only in two of the above treatments R6 and R9. The Rhizobium culture R5 isolated from C.S.R.C. Karamana, Trivandrum was found superior to all other local isolates of rhizobia. Besides the required minimum increase in dry weight of plants from Rhizobium inoculation, 50 per cent increase in dry mass over uninoculated control (as per the Indian Standard Institution Specifications for Rhizobium inoculants is 0268-1976) was obtained only with this isolate of Rhizobium.ennullThesis