Agriculture Reference
In-Depth Information
degraded areas. Therefore, by adding beneficial microorganisms in the
rhizosphere, the use of AMF-infected plants could reduce the amount of
inorganic fertilizers needed for production.
14.3.6 MANAGEMENT OF SOIL-BORNE PATHOGENS
AMF are known to act against soil-borne diseases leading to reductions
in incidence and/or severity of root rot or wilt caused by fungi such as
Rhizoctonia
,
Fusarium
,
Verticillium
,
Phytophthora
,
Pythium
and
Aphano-
myces
. The phenomenon of AMF protecting plants from root pathogens is
known from studies involving root-infecting pathogens, for example,
Phy-
tophthora parasitica
or
Fusarium
sp., root-invading nematodes and hor-
ticultural species.
Glomus mosseae
induced local and systemic resistance
to
P. parasitica
and was effective in reducing symptoms produced by the
pathogen. Mycorrhizal plants exhibit increased tolerance towards fungal
root diseases causing wilts and rots owing to better cuticulized with more
lignified xylem element, allowing increased flow of nutrients, greater me-
chanical strength and reduced impact of harmful pathogens.
Colonization of plant roots by AMF has been shown to lead to reduced
damage by nematodes (Azcon-Aguilar and Barea, 1996). Plant parasitic
nematodes are among the most common pest constraint to banana produc-
tion (Gowen et al., 2005). The benefits of AMF in nematode management
in banana has been demonstrated by Elsen et al. (2004), who showed that
AMF could suppress
Radopholus similis
densities by almost 50% in pots.
Fernández et al. (2003) also demonstrated that colonization by
Glomus
spp., particularly
G. intraradices
,
G. manihotis
and
G. mosseae
could sig-
nificantly reduce nematode damage caused by
R. similis
and
Meloidogyne
incognita
on banana in pots. In Cameroon, inoculation of a
Glomus
spp.
on plantain in pots significantly suppressed
R. similis
(Fogain and Njifen-
jou, 2002).
Phenols and enzymes such as polyphenol oxidase are important com-
ponents of plant defense mechanism against the diseases. Dual inoculation
with AMF and
Rhizobium
markedly increased the level of leaf chlorophyll,
total soluble sugars, total phenols and free amino acids content in roots
compared with those inoculated only with
Rhizobium.
Mycorrhizal forma-
tion is positively correlated with relative turgidity, activities of peroxidase
and polyphenol oxidase (catechol oxidase), available phosphorus and total
