Chemistry Reference
In-Depth Information
Mesorhizobium and Rhizobium.
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The technique has been used in numerous
studies of African soils which have revealed rhizobia diversity of the LNB in
African soils. For instance, identification of the genus Methylobacterium in
Senegal by Sy
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and Samba et al.
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reported a total of 117 strains of both slow-
and fast-growing rhizobia from roots of Crotolaria species in Senegal. Similarly,
Odee et al.
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identified five bacteria genera, namely Agrobacterium,
Bradyrhizobium, Mezorhizibium, Rhizobium and Sinorhizobium, for root nodules
of legumes growing in diverse soils in Kenya, while Anyango et al.
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found that
beans grown in acid soils in Kenya were nodulated by different rhizobia species.
In a recent study which assessed the abundance of LNB in soils of the Embu and
Taita Districts in Kenya, Mwenda et al.
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and Mwangi et al.
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obtained similar
rhizobia diversity to Odee et al.
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and their diversities were positively influenced
in cropping systems.
Legume inoculation is a process through which leguminous crops are
provided with the effective bacterial strain of the genus Rhizobium which
results in an effective symbiotic relationship that brings about fixation of
atmospheric nitrogen into organic nitrogenous compounds in the plant.
However, response to rhizobia inoculation is influenced by a number of factors
which include soil nitrogen, rhizobia strain and populations of indigenous
populations, crop and environmental conditions.
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Despite these challenges,
inoculant production has going on for several decades by both private and
public institutions in Africa to harness benefits of the Legume-Rhizobium
technology and about 100 000 tonnes of rhizobia inoculants are produced in
Kenya, South Africa, Zambia and Zimbawe for inoculating food legumes such
as soya bean, beans and also for fodder crops.
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5.4.2 Arbuscular Mycorrhizal Fungi (AMF)
Arbuscular mycorrhizal fungi (AMF) are common root-colonising fungi
forming symbioses with most plants. The AMF are globally widespread and
are associated with most plant species.
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These fungi have been reported
from diverse natural ecosystems including deserts, sand dunes, tropical forests,
salt marshes, and in managed systems such as pastures, orchards and field
crops.
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In agricultural systems, edaphic factors, land use, cropping systems
and management practices interact to influence AMF species composition and
spore population. Consequently, changes in agricultural practices will
inevitably lead to a change in the overall abundance of propagules of each
fungus within a population.
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Studies carried out on the distribution of AMF
in legume-based systems in Nigeria showed prolific arbuscular mycorrhizal
colonisation in the roots.
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Shepherd et al.,
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on the other hand, found forest
and grassland soils to have narrower species distribution than most farm soils,
indicating some degree of ecosystem adaptation. In a survey carried out in the
Mount Kenya region, across different land-use types (LUTs), a total of 16
AMF species were isolated.
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The spore community was dominated by
Acaulosporaceae and Glomaceae. Land-use type had no significant effect on
