Phenotypic and Symbiotic Characterization of Grass Pea (Lathyrus Sativus) Rhizobial Isolates from Some Major Growing Areas Of South Wollo and West Shoa , Ethiopia
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Date
2009-07
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Addis Ababa University
Abstract
Grass pea (Lathyrus sativus) is the most widely distributed and the third most important pulse
crop in Ethiopia. It grows in a wide range of altitudes and survives in scarce moist conditions and
fixes nitrogen with rhizobia and performs well in less fertility soils. However, the effectiveness in
nitrogen fixation varies depending upon the host varieties, type of strain and different
environmental characters. It is, therefore, necessary to evaluate the efficiency of different isolates
from different sampling areas. Thus, 68 grass pea rhizobial isolates (47 from South Wollo and 21
from West Shoa) were isolated and characterized on the basis of different characters. These
isolates were reinoculated on pouch culture using “Wasse” variety of grass pea to authenticate
nodulation and determine their symbiotic effectiveness. All but 5 isolates were authenticated as
root nodule bacteria with their capacity to infect and nodulate their parent host. Most of the
isolates displayed fast doubling time (1.2-4hrs) and large colonies (2-6.0 mm) and changed the
BTB-YEMA media to yellow which showed that they are fast growing rhizobia and then
categorized into R. leguminosarum bv. viceae. The preliminary screening of the isolates for
symbiotic effectiveness on pouch culture showed that isolates AAUGR (31, 37, 41 and 47) of
South Wollo and AAUGR (48, 49, 52, 59, 60, 61, 66 and 67) of West Shoa that comprised of
19% of the isolates were highly effective whereas, 43% were found to be effective. Three highly
effective isolates from South Wollo (AAUGR 31, AAUGR 37, and AAUGR 41) and four highly
effective isolates from West Shoa (AAUGR 48, AAUGR 59, AAUGR 61, and AAUGR 67) were
reinoculated into soil culture to evaluate their performance in the natural environment (soil). All
the selected isolates were found to accumulate 112-149 % of SDM that was higher than the
controls. Isolate AAUGR 37 (SW) accumulated the highest SDM of all the inoculated treatments
and the controls. All the selected isolates were found to perform better on pot culture than on
pouch culture. Almost all of the isolates were able to grow at extremely low and high pH, low and
high salt, low and high temperature, and utilized a wide range of carbohydrate and nitrogen
sources and displayed high resistance to several antibiotics indicating that the isolates can
compete in their natural environment. The result of the numerical analysis also showed the
existence of diversity among the tested isolates.
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Biology