Dixit et al.
MTCC2378
+
+
-
-
-
-
MTCC103
+
+
+
-
-
-
MTCC129
+
+
-
++
+
+
MTCC1934
-
-
-
+
-
+
MTCC297
+
+
+
+
+
+
MTCC 441
+
+
+
-
-
-
MTCC 122
+
+
-
-
-
-
abbreviation: +++ very good production; ++ good production; + positive; - negative;
Rhizobium Leguminosarum MTCC99, Sinorhizobium meliloti MTCC100, Mesorhizobium
loti MTCC2378; Pseudomonas fluorescens MTCC103, Pseudomonas sp. MTCC129,
Pseudomonasaeruginosa MTCC1934, Bacillus sp.MTCC297, Bacillussubtilis MTCC441,
Paenibacillus polymixa MTCC122.
Among 152 isolates, only 27 isolates were found to have plan growth promoting traits viz. ,
IAA, HCN, ammonia, siderophore production, phosphate solubilisation and antagonism
against Fusarium oxysporum (Table 3). Some endophytic bacteria have the potential to
synthesize IAA by using tryptophan as the precursor. All the isolates were found to be
positive for IAA production as observed by the development of pink color in the cell free
supernatants and its production was induced in the presence of tryptophan. Six isolates
(RT1, RT2, RT7, RT9, RT19 and RT22) produced the maximum amount of IAA. The
ability of the production of IAA by different bacteria isolates has also been reported by
many researchers (Lata et al., 2006; Kumar et al., 2012).The bacterial isolates formed
clear halos zone around the inoculated spot which indicate phosphate solubilisation on the
Pikovaskya’s agar medium.Among all, nine isolates viz., RT1, RT2, RT4, RT6, RT10, RT18,
RT23, RT24 and RT26 showed to solubilize the maximum amount of inorganic phosphate.
All the isolates produced cyanogen and siderophore onto their respective media. Only two
isolates (RT1 and RT2) were found good in siderophore production, while the other six
isolates (RT1, RT2, RT10, RT12, RT18 and RT21) were good in HCN production.
All selected strains were found ammonia producer but among them only four isolates
(RT1, RT2, RT9 and RT11) were good ammonia producer. Similar results have also been
reported for phosphate solubilization (Kumar et al ., 2011), siderophore production (Kumar
et al ., 2011), HCN production (Ahmad et al ., 2008), IAA production (Lata et al., 2006),
and ammonia production (Selvakumar et al ., 2008). Isolates RT1, RT2, RT10, RT12 and
RT18 showed strong growth inhibition in vitro against Fusarium oxysporum . Antagonistic
properties by the isolates may be explained to be due to the production of antibiotics, HCN,
and siderophore production, resulting in fungal growth inhibition. Similar works have been
reported in other studies (Dubey and Gupta, 2012; Kumar et al ., 2012). However, role of
other inhibiting molecules such as toxins and enzymes in the growth inhibition process of
the fungal pathogens cannot be ruled out. Growth inhibition of F. oxysporum (Kumar et
al., 2011) and M. phaseolina (Dubey and Gupta, 2012) has also been reported. Besides,
several other factors such as staling growth products, pH of growth media, composition
for nutrients and space and nutrient imbalance caused due to nutrient impoverishment may
also be involved in microbial antagonism.
106
Int. J. Bioinformatics and Biological Sci.: v.2 n.1&2, p. 95-109. March & June 2014