Bioscience Methods 2015, Vol.6, No.3, 1-9
6
by
T. virens
(57.7%) and
T. koningii
(55.5%) over
M. phaseolina
were recorded minimum but these
were also significant.
3.3 Bell’s Scale
According to modified Bell’s scale,
T. harzianum
overgrew beyond 90 percent (R
1
scale). In case of
R.solani
, only
T. koningii
overgrew beyond 60 percent
(R
3
scale).All
Trichoderma
species were failed to
progress beyond 60 percent (R
3
scale) in
A.niger
. In
G.candidum,
T. pseudokoningii
and
T. viride
overgrew
at least two third of pathogen (R
2
scale) but others
were beyond 60 percent (R
3
scale). In case of
F.oxysprum f. sp.spinaceae, T. virens
overgrew at least
two-third pathogens (70% over growth). Except
T.
koningii
and
T. virens
other
Trichoderma
species were
overgrew at least two third of pathogen (R
2
scale) in
M.
phaseolina
(Table 4).
Table 4 Evaluation of
Trichoderma
spp. against pathogenic fungi by dual culture using Bell’s scale*(R).
Trichoderma
spp
Test Pathogens
A.alternata
R.solani
A.niger
G.
.
candidum
F.oxysporum
M. phaseolina
T. viride
R
2
R
4
R
4
R
2
R
3
R
2
T. harzianum
R
1
R
4
R
3
R
3
R
3
R
2
T. koningii
R
2
R
3
R
3
R
3
R
3
R
3
T. pseudokoiningii
R
2
R
4
R
4
R
2
R
3
R
2
T. virens
R
2
R
4
R
4
R
3
R
2
R
3
Note: *Degree of antagonism
R
1
=
Trichoderma
completely overgrew pathogens (100% over growth);
R
2
=
Trichoderma
overgrew at least two-third pathogens (75% over growth);
R
3
=
Trichoderma
colonizes on one half of the pathogens (50% over growth);
R
4
=
Trichoderma
and the pathogens contact point after inoculation;
R
5
= Pathogens overgrow bioagent –
Trichoderma.
4 Discussion
Experiments were also conducted to determine the
compatibility of biocontrol agents with commercially
effective chemicals against white rot of apple
(
Dematophora necatrix
) in India (Gupta and Sharma, 2004).
They concluded that Carbendazim was inhibitory to all
fungal antagonists whereas Mancozeb and Phorate were
least inhibitory at 200ppm. Radial growth of mycelium of
Trichoderma
spp was inhibited at Carbendazim @ 1ppm
and Triphonate Methyl @ 10ppm (Malathi et al., 2002).
Inhibitory action of Isofenphos – methyl on
T. harzianum
was strong and fungistatic rate was 64.37% under treatment
with 200μg/ml (Chinh et al., 2008). The fuingicide
Iprodione and
T. harzianum
were not found to be
compatible (Sumitra and Madhuban, 2006). The
T.
harzianum
was least sensitive to Procymidone and Captan
and most sensitive to Mancozeb, Tebuconazole and Thiram
(Mclean et al., 2001). Inhibitory effect of Carbendazim and
Thiophanate Methyl on
T. harzianum
while Captan and
Thiram recorded least inhibitory effect on
T. harzianum
(Gowdar et al., 2006). Recently, the fungicide Bordeaux
mixture 1% found highly inhibitory to
Trichoderma
as
compared to Copper oxychloride and Mancozeb (Suseela
and Joseph, 2010). Some strains of
Trichoderma
show
compatibility with fungicides as they are tolerant of
fungicides and successfully used in IPM strategy (Dutta and
Chatterjee, 2004; Hetong et al., 2008).
Trichoderma viride
was not compatible with Dithane, Bavistin and Ridimil in
any level of selected concentration (Tapwal et al., 2012)
Many workers in the discipline of plant pathology
suggested that growth of plant pathogenic fungi were
inhibited by the
Trichoderma
species because of some
factors produced and these substances may be volatile
and non volatile (Reusser, 1967).The growth
inhibition of pathogenic fungi may be due to antibiotic
secretion like trichodermin, trichoviridin, dermadin
and sesquiterpene heptalic acid (Nakkeeran et al.,
2002), nutrient impoverishment and pH alteration in
the medium (Maheshwari et al., 2001). Such type of
variability in antagonistic potential of
Trichoderma
species against plant pathogens has been also reported
(Saha and Pan, 1996; Bell et al., 1982). Mathew and
Gupta (1998) also reported that
T. harzianum
also
exhibited maximum antagonistic activity causing 58%
inhibition followed by
T. viride
(46%) and
T. virens
(45%). Isolates of
T. viride, T. harzianum
and
T. virens
were evaluated for their antagonism against
Pythium
aphanidermatium
causing damping off of tomato and
found that many isolates inhibited the growth of
P.
