2.3.5 Effect of Insecticides on Plant Growth Promoting
Attributes
Indole acetic acid (IAA) is produced by different rhizobacterial strains belonging to
Serratia, Bacillus, and Pseudomonas even under exposure stress of residual insecticide but decreased consistently with increasing insecticide concentration among all
bacterial strains (Wani et al. 2005). Ahemad and Khan (2011) reported that substantial IAA was produced by the Klebsiella sp. strain PS19 even when exposed to three
times the recommended dose of insecticides. In addition, Azotobacter species was
found to fix nitrogen, produced hormones IAA, gibberellic acid (GA) and solubilized phosphate in the media containing a variety of pesticides (Chennappa et al.
2014; Gurikar et al. 2016). Castillo et al. (2011) found that endosulfan did not affect
IAA production in Azotobacter chroococcum and very few differences were found.
On the other hand, Asma et al. (2012) reported the effect of endosulfan on IAA
production in Azotobacter and found that even 50 ppm of endosulfan inhibited IAA
production. The effect of pesticides (chlorpyrifos and phorate) on IAA production by
Azotobacter species was observed at different concentrations compared to control
(Chennappa 2016). The highest IAA-producing Azotobacter salinestris
supplemented with 1 mg tryptophan at 1% chlorpyrifos indicated that 1% chlorpyrifos did not affect bacterial growth and function. Significant differences were
recorded in the different isolates at 3% and 5% phorate, and A. salinestris produced
the maximum IAA at 5% phorate (Chennappa 2016). Similarly, Azotobacter species
that are resistant to pesticides isolated from paddy soils produce IAA in media
supplemented with 5% pesticides (Chennappa et al. 2013).
Gibberellic acid (GA) is one more important plant growth substance produced by
plant growth–promoting rhizobacteria (PGPR) of various species, including Azotobacter species. Asma et al. (2012) reported the effect of endosulfan on GA production in Azotobacter, and 50 ppm concentration of endosulfan was found to inhibit
GA production. Azotobacter salinestris isolate produced a maximum of GA at 1%
chlorpyrifos (Chennappa 2016). Higher than 1% concentration, chlorpyrifos reduced
the GA production capacity of Azotobacter and also reduced bacterial growth by
20–25%.
Castillo et al. (2011) reported that endosulfan at 2–10 mg L
À1 inhibited 94% and
96% of the nitrogenase activity of the Azotobacter chroococcum but
A. chroococcum completely degraded endosulfan. Of the total five isolates, the
highest nitrogen fixation was observed with A. salinestris isolate at 1% phorate
concentration (Chennappa 2016). Moneke et al. (2010) reported that Azotobacter
and other bacterial species, such as Pseudomonas, Escherichia, and Acetobacter,
were tolerant and degraded glyphosate herbicides, and all the isolates were resistant
to 1%, 3%, and 5% pesticides, although the bacterial activity was inhibited compared
to control. Wani et al. (2005) assessed the toxic effects of different types of
pesticides on the solubility of phosphate of 12 bacteria on phosphate, isolated
from various rhizospheric soils such as Serratia, Pseudomonas, and Bacillus.
Among various bacterial cultures, Serratia exhibited the highest phosphate
32
A. Sehrawat et al.
Attributes
Indole acetic acid (IAA) is produced by different rhizobacterial strains belonging to
Serratia, Bacillus, and Pseudomonas even under exposure stress of residual insecticide but decreased consistently with increasing insecticide concentration among all
bacterial strains (Wani et al. 2005). Ahemad and Khan (2011) reported that substantial IAA was produced by the Klebsiella sp. strain PS19 even when exposed to three
times the recommended dose of insecticides. In addition, Azotobacter species was
found to fix nitrogen, produced hormones IAA, gibberellic acid (GA) and solubilized phosphate in the media containing a variety of pesticides (Chennappa et al.
2014; Gurikar et al. 2016). Castillo et al. (2011) found that endosulfan did not affect
IAA production in Azotobacter chroococcum and very few differences were found.
On the other hand, Asma et al. (2012) reported the effect of endosulfan on IAA
production in Azotobacter and found that even 50 ppm of endosulfan inhibited IAA
production. The effect of pesticides (chlorpyrifos and phorate) on IAA production by
Azotobacter species was observed at different concentrations compared to control
(Chennappa 2016). The highest IAA-producing Azotobacter salinestris
supplemented with 1 mg tryptophan at 1% chlorpyrifos indicated that 1% chlorpyrifos did not affect bacterial growth and function. Significant differences were
recorded in the different isolates at 3% and 5% phorate, and A. salinestris produced
the maximum IAA at 5% phorate (Chennappa 2016). Similarly, Azotobacter species
that are resistant to pesticides isolated from paddy soils produce IAA in media
supplemented with 5% pesticides (Chennappa et al. 2013).
Gibberellic acid (GA) is one more important plant growth substance produced by
plant growth–promoting rhizobacteria (PGPR) of various species, including Azotobacter species. Asma et al. (2012) reported the effect of endosulfan on GA production in Azotobacter, and 50 ppm concentration of endosulfan was found to inhibit
GA production. Azotobacter salinestris isolate produced a maximum of GA at 1%
chlorpyrifos (Chennappa 2016). Higher than 1% concentration, chlorpyrifos reduced
the GA production capacity of Azotobacter and also reduced bacterial growth by
20–25%.
Castillo et al. (2011) reported that endosulfan at 2–10 mg L
À1 inhibited 94% and
96% of the nitrogenase activity of the Azotobacter chroococcum but
A. chroococcum completely degraded endosulfan. Of the total five isolates, the
highest nitrogen fixation was observed with A. salinestris isolate at 1% phorate
concentration (Chennappa 2016). Moneke et al. (2010) reported that Azotobacter
and other bacterial species, such as Pseudomonas, Escherichia, and Acetobacter,
were tolerant and degraded glyphosate herbicides, and all the isolates were resistant
to 1%, 3%, and 5% pesticides, although the bacterial activity was inhibited compared
to control. Wani et al. (2005) assessed the toxic effects of different types of
pesticides on the solubility of phosphate of 12 bacteria on phosphate, isolated
from various rhizospheric soils such as Serratia, Pseudomonas, and Bacillus.
Among various bacterial cultures, Serratia exhibited the highest phosphate
32
A. Sehrawat et al.