Abstract:
A pot experiment was conducted to test the efficiencyof two Rhizobium strains;
in fixing atmospheric nitrogen one strain from Sudan: (ENRRI16a) ,isolated
from central Sudan, and a commercial strain, ICRISAT 7001 isolated from
India on three Sudanese groundnut cultivars, selected in Sudan as high yielders;
Ahmedy, Tozy and Bunting.
The tested Rhizobium strains on the groundnut cultivars used did not supply the
cultivars with the needed nitrogen for optimum growth as evidenced by the
finding that mineral fertilizer added as urea consistently outyielded all the
Rhizobium strains added as inoculums in shoot weight followed by strain
ENRRI16a when applied at a high inoculums dose (4×106 CFU /ml).
The cultivars tested, however, interacted differently with the Rhizobium strains
depending on the inoculums dose, and to mineral nitrogen added as urea. The
VI
Bunting cultivar was very responsive to mineral nitrogen addition. Ahmedy
cultivar did not form any nodules with the local strain from Sudan when added at
two different doses which indicated incompatibility between the Rhizobium
strain and some of the tested cultivars. The local strain formed nodules with the
other two cultivars with a noticed trend of higher infectivity and efficiency with
the Bunting cultivar. Similar trend was reported with the nodule dry mass. This
confirmed the significance of the right selection of the right cultivar for the right
Rhizobium
The cultivars responded differently to inoculums doses. In response to the
addition of high inoculums dose, strain ENRRI16a, however when applied at a
lower dose significantly out yielded the control with Tozy and Bunting cultivars,
while giving a lower shoot weight with Ahmedy cultivar. The performance of
the other Rhizobium strain; ICRISAT7001 at the high dose of inoculum was
comparable with mineral nitrogen addition as well as with the ENRRI16a strain.
Similar trend was noticed with the root dry weight.
These findings were not reflected in plant tissue nitrogen content, which may be
attributed to the short duration of the experiment.
It is clear from this study that both added Rhizobium strains were not able to
supply the groundnut cultivars with the required nitrogen for optimum growth,
despite their variability in performance.
Further research is stressed I the future to mark the added Rhizobium strains,
whether local or exotic to determine nodules occupancy and correlate it with the
measured nitrogen fixation traits to offer further help in recommending the
suitable Rhizobium strain to be used with the optimum inoculums dose and with
the compatible groundnut cultivar.
