MSc

The 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 CO-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 118.33 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 8268-1976) was obtained only with this isolate of Rhizobium.

The multilocational field trial for studying the varietal variation for nodulation by Rhizobium was conducted at two different locations in Trivandrum district at Karamana and Pattom using five varieties of green gram and two cultures of rhizobia. The effect of Rhizobium inoculation in increasing the nodule number in different varieties of greengram was significant at both locations when compared to that of control. The mean number of nodules formed per plant, 220.59 at Karamana and 202.22 at Pattom were maximum due to seed inoculation with the standard culture of Rhizobium. Among different varieties of greengram the maximum number of nodules were formed in CO-3 both at Karamana and Pattom. However, there was no significant differences between varieties in their mean nodule number. The fresh and dry weights of nodules were also significantly high due to Rhizobium inoculation at both locations. The mean fresh and dry weights of 1.42 g and 140.14 mg respectively at Karamana and 1.44 and 146.o mg respectively at Pattom were maximum in seed treatment with the local isolate of Rhizobium. The fresh weight of shoot was significantly high due to Rhizobium inoculant at both locations when compared to that of control. The mean fresh weight of 150.2 g was maximum in seed treatment with the standard culture of Rhizobium at Karamana and with the local culture of Rhizobium at Pattom. It was also observed that the dry weight of shoot was significantly high due to Rhizobium inoculation at both locations. The mean dry weight of 25.2 g was maximum in seed treatment with the standard culture of Rhizobium at Karamana. The increase in dry weight of shoot due to seed inoculation with the local culture of Rhizobium at locations were also significant and statistically on par with the above treatment. There were no significant difference between varieties in their mean dry weight of shoot at both locations.

The increase in mean yield (g/plot) of different varieties of greengram due to Rhizobium inoculation was significant at both locations when compared to that of control. The mean yield of 1005.0 g at Karamana and 966.6 g at Pattom were maximum in seed treatment with the standard culture of Rhizobium. However, the increase in yield in different varieties of greengram due to seed inoculation with the local culture of Rhizobium was also significant when compared to that of control and at one location, Pattom, this increase was even statistically on par with the standard culture or Rhizobium. Significant differences between varieties in their mean yield were observed at both locations. The mean yield of 1055.3 g at Karamana and 1015.6 g at Pattom were maximum in the variety CO-3 followed by varieties such as CO-4, CV-2, KM-2 and Pusa baisakhi. A significant interaction between Rhizobium inoculation and different varieties of greengram was however absent.