Variations in infectivity of indigenous rhizobial isolates of some soils in the rainforest zone of Nigeria
Date
2015Author
Ojo, Abisoye
Dare, Michael Olajire
Fagbola, Olajire
Babalola, Olubukola
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Show full item recordAbstract
Nodule formation in legumes is a process that starts with root infection by rhizobia.
The present study assessed the population and infectivity of the indigenous rhizobial
strains in rainforest soils of Nigeria. Soils were collected from three sites – Idi-
Ayunre, Orile-Ilugun (OI) and the University of Ibadan Teaching and Research Farm
(UITRF) – and analysed for physico-chemical properties and rhizobial population.
Soybean varieties TGx1448-2E and TGx1456-2E and a cowpea variety IT89KD-288
were planted as trap crops on each of the soils, and rhizobia were isolated from their
nodules. Infectivity assay was conducted using eight varieties of soybean and a cowpea
variety. Most probable number estimate of the rhizobial population showed that the
UITRF had significantly higher rhizobial population than the other two locations. OI
and the UITRF soils planted with TGx1448-2E had significantly higher nodules and
number of strains than other treatments. Among the 70 slow-grower strains isolated,
only nine were infective. Three of the nine strains – IDC8, TRC2 and OISa-6e –
nodulated at least seven of the eight soybean varieties used for infectivity test.
Indigenous rhizobial infectivity of the studied locations was low, and cultivation of
grain legume may require rhizobial inoculation for high productivity.