Abstract:
Grass pea (Lathyrus sativus) is an insurance crop grows extensively in the world and has
symbiosis interaction with nitrogen fixing rhizobia. Farmers used glyphosate as weed control
in agricultural process. However, the application this chemical herbicide affects soil fertility
by decreasing nitrogen fixing rhizobia. The objective of this study was to assess the effects of
glyphosate on the Rhizobium isolate. Grass pea with good growth and healthy appearance
were selected purposefully form the field and rhizobia was isolated from root nodules.
Isolates were characterized on the basis of their morphological, biochemical characteristics
and resistance of abiotic condition. Isolates of rhizobia from grass pea were gram negative;
circular, milky, 2-4.1mm diameter and most of them are smooth colony appearance on
YEMA. Based on the morphological and biochemical characteristics of isolates were grouped
under the genus Rhizobium. Isolates was grown best at the temperature between 28-38 , pH
5-8 and at 0.5 and 1% salt concentration. Glyphosate was found to affect the survival of
Rhizobium under laboratory. 5.52-47% of Rhizobium population was inhibited at 20ml L
concentration of glyphosate. At the concentration of 40mlL
-1
percentage of inhibition was
17.1% - 53.38%. However, 87% of isolates were inhibited with higher concentration (60ml
L
−1
) of glyphosate. The number of colonies after the exposure of glyphosate was greatly
dependent on concentration. Thus isolate from root nodules of grass pea was inhibited by
glyphosate under laboratory condition. Future work needs to identify resistant Rhizobium
from grass pea root nodule through evaluating their responses under greenhouse and field
conditions and used as microbial inoculum.