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Full Length Research Paper
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Host range, symbiotic
effectiveness and nodulation competitiveness of some
indigenous cowpea bradyrhizobia isolates from the
transitional savanna zone of Ghana
Osei Yaw Ampomah2, Emmanuel Ofori-Ayeh1,
Bjorn Solheim2 and Mette Marianne Svenning2*
1Biotechnology
and Nuclear Agriculture Research Institute, Ghana Atomic
Energy Commission, P.O. Box LG 80, Legon, Accra, Ghana.
2Department
of Biology, Faculty of Science, University of Tromso, 9037
Tromso, Norway.
*Corresponding author: E-mail:
Mette.svenning@ib.uit.no.
Tel: +4777644432. Fax: +4777646333.
Accepted
16 February, 2008 |
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Abstract |
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To
identify indigenous rhizobia with potential as inoculants
for increasing cowpea (Vigna unguiculata) yields, we
have assessed the host range, symbiotic effectiveness and
competitiveness for nodule occupancy among five (AII-2-1,
AII-5-2, AI-4-3, AII-3-4 and BIII-2-2) indigenous cowpea
bradyrhizobia isolates from the transitional savanna zone of
Ghana. ERIC-PCR DNA fingerprinting patterns were used to
identify the isolates occupying nodules. All the isolates
nodulated cowpea, groundnut (Arachis hypogeae) and
mungbean (Vigna radiata), but only AII-2-1, AII-3-4
and BIII-2-2 nodulated soybean (Glycine max). Apart
from cowpea where all the isolates were effective, there
were significant differences in the symbiotic effectiveness
of the isolates on the other host legumes. Out of a total
of about 250 cowpea nodules that were screened for each
inoculum-mix, isolate AII-5-2 was the most competitive for
nodule occupancy whilst AII-3-4 was the least. Isolate
AII-5-2 occupied 71% of the nodules in an inoculum-mix
consisting of equal proportions of AII-2-1, AII-5-2 and
AI-4-3 (a 3-isolate-mix) and 60% of nodules in an inoculum-mix
consisting of equal proportions of all the five isolates (a
5-isolate-mix). Therefore, among the isolates tested,
AII-5-2 has the best potential for use as inoculant for
maximizing cowpea yield in N2- deficient
agro-ecological zones of Ghana.
Key
words:
Competition, legumes, nitrogen fixation, rhizobia,
symbiosis. |
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