Effect of Two Azospirill Um Isolates on the Growth and Nitrogen Content of Tef (Eragrostis Tef (Zucc.) Trotter)
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Date
1998-06
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Addis Ababa University
Abstract
Two diazotrophic bacteria, coded as A31 and A32, were isolated from roots of the lefvarieties
DZ-01-354 and DZ-01-196, respectively grown in pots on loam soil from Debrezeit. These
isolates were characterized to the generic level and further comparison with the description of
the type cnltures Azospirillum lipoferum (ATCC 29707) and Azospirillum brasilense (ATCC
29145). These comparisons showed that the two isolates closely resemble A. lipofernm .
However, on the basis of some differences in biochemical characteristics, it was suspected that
these isolates may be different strains of A. lipoferum.
In an attempt to investigate the effect of these isolates on the yield and nitrogen content of tef,
inoculation studies on pot grown tef plants was conducted. Root inoculation of seedlings of the
two tef varieties with Iml sterile water suspension (107-10' colony forming units (cfu) Iml ) of
these isolates produced significant (p < 0.05) increases in height, grain yield, total shoot and
root weight, root shoot ratio, total grain nitrogen and protein content of grains. Grain yield
increases up to 11. 6 % and total nitrogen and protein content of grains up to 5.7 % over and
above un inoculated controls were observed.
The bacterial isolate A32 has performed better than A31 in promoting growth and yield of
both varieties. Differential plant responses due to different bacterial treatments was found to be
significant (p < 0.05) for parameters as height, root shoot ratio and total nitrogen and protein
content of grains on both varieties. Of the two tef varieties Dz-01-196 responded better than
DZ-O 1-354 to inoculation with either of the isolates as demonstrated in a higher percent
increases over the respective controls for most growth parameters The existence of a possible
specific interaction between host cultivar and bacterial isolate which governs plant yield
responses was suspected. Finally, the potential role of Azospirillum inoculation of tef seedlings
on reducing fertilizer requirements was discussed.
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Biology