Agriculture Reference
In-Depth Information
Jaffee et al.
1998
; Jaffee
2002
; Jaffee and other animal dung might Strong
2005
). Re-
cently, Kumar and Singh (
2006
) reported that application of
A. dactyloides
reduced
the number of root knots in tomato and increased plant growth in pots. The effect of
A. dactyloides
was enhanced when its mass culture was applied in combination with
cow dung manure. Similar results on reduction of root knot nematodes in rice plants
were observed by Singh et al. (
2006
) by nematode-trapping fungi
A. oligospora
with
cow dung manure. Similar type of biocontrol efficacy of nematode-trapping fungi
was also observed by several researchers when applied in combination with compost
(Matskevich et al.
1978
) and organic substrates (Gueye and Duponnois
1997
; Du-
ponnois
1995
; Ashour
1999
). Sayre and Walter (
1991
) remarked that where biologi-
cal control has been achieved through use of trapping fungi, the results may have
been confounded by the abundance of organic material that was added as food base
for these fungi.
In another experiment (Fig.
12.2c,d
), biotic stress reduced significantly when the
amount of mass culture of
A. oligospora
was increased in the nematode-infested
soil. This clearly indicates that application of mass culture at higher concentration
reduces more number of root knots which indirectly helped in plant growth. This
is quite expected as the predaceous activity would be increased with increase in
amount of mass culture inoculum.
Similar experiments on the time of application of mass culture of
A. oligospora
showed even more reduction in root knots in both tomato and brinjal when mass
culture was applied one or two weeks prior to planting in the nematode-infested soil
(Fig.
12.2e,f
).
From the observation, it is obvious that irrespective of treatments in different
experiments, reduction in number of root knots was higher in 30-day-old plants in
comparison to 60-day-old plants, which clearly indicates that nematode-trapping
fungi is more effective during the early growth stages of plants. The higher percent-
age of reduction at early growth stage of plants may be attributed to increase in pre-
daceous activity of the nematode-trapping fungi. It is a well-established fact that the
early infection in plants by root knot nematode causes biotic stress as acute stunting
of the plants whereas delayed infection at later stage of plants may not show even
perceptible stunting. This type of reaction may be due to varying ratio of nematode
biomass and root biomass of the plants.
3.1 Mycoparasitism
Mycoparasitism is a characteristic of fungi that obtain nutrition either directly or
indirectly from another fungi through various mechanisms (Jeffries
1997
). The abil-
ity of nematode-trapping fungi to attack other fungi was first time noticed by Tzean
and Estey (
1978
). Nematode-trapping fungi such as
A. oligospora
formed hyphal
coiling around the fungus
Rhizoctonia solani
in a similar manner as formed by
Trichoderma
species (Chet et al.
1981
). It has been confirmed by using radioactive
phosphorus tracing that considerable amount of phosphorus transfer takes place
between the hyphae of
R. solani
to nematode-trapping fungi
A. oligospora
(Ols-
