profiles have been observed in this study. The molecular weight of the observed
bands in SDS-PAGE was correlated with the molecular weight of dipteran active
proteins. Based on this comparison, several protein profiles corresponded to the
specific Cry or Cyt proteins toxic for dipterans (molecular masses of 17–28 kDa
correspond to Cry17 and Cyt, 50 kDa to Cry2Ab, 65–75 kDa to Cry2Aa, Cry2Ac,
Cry4D, Cry17A, Cry19 and Cry24, 80 kDa to Cry4C and Cry11B, and 128–140 kDa
correspond to Cry4A, Cry4B, Cry32). The protein profile analysis revealed a great
diversity of protein patterns within the Iranian Bt collections.
10.8.5 Biological Activity
All the mentioned means of characterization; parasporal crystal morphology, biochemical experiments, PCR-screening and SDS-PAGE analysis, are being used to
predict the insecticidal activity of newly isolated Bt strains. Therefore, performing
bioassays provides complementary information on the biological activity of the
isolated Bt strains. Moreover, the final goal of these studies is to introduce a highly
potent and effective Bt strain for biological pest control. Therefore, many studies
were carried out to evaluate the insecticidal activity of Iranian Bt strains or Iranian
commercial Bt-based products.
The bioassays with the Bt strains harboring genes encoding proteins active for
lepidopterans were carried out against the cotton bollworm, Helicoverpa armigera
Hüber (Lep.: Noctuidae). Several strains with high insecticidal activity have been
introduced as good candidates for biocontrol of this pest (Seifinejad et al. 2008). The
Bt strains containing coleopteran-active cry genes, were bioassayed against the elm
leaf beetle, X. luteola first instar larvae (Nazarian et al. 2009), leading to the
identification of novel cry genes based on the PCR analysis and also the introduction
of potent Iranian Bt strains for biological control of coleopteran insect pests,
particularly X. luteola. With the aim of finding the nematicidal Bt strain, 70 Bt
isolates available in the Bt collection of Agricultural Biotechnology Research
Institute of Iran (ABRII) were characterized. Based on the presence of the cry
genes active against nematodes, the nematicidal activity of these Bt strains against
Meliodogyne incognita, Chiloplacus tenuis and Acrobeloides enoplus were evaluated (Salehi Jouzani et al. 2008c). Based on the bioassays, two strains YD5 and
KON4 were toxic to M. incognita, and two studied free-living nematodes, C. tenuis
and A. enoplus, were susceptible to strains SN1 and KON4 (Salehi Jouzani et al.
2008c).
In several cases, the screening and characterization studies led to the introduction
of potent Bt strains to industrial sections for mass production. The Iranian strains
isolated from soil and infected larvae were thoroughly characterized (Khorramnejad
et al. 2018). Bt strains with diverse larvicidal activity against Indian meal moth,
P. interpunctella, were selected and characterized by employing different techniques. The insecticidal activity of selected Bt strains was investigated against
different lepidopteran pest species; Spodoptera exigua, Mamestra brassicae,
10 Progress on the Bacterium Bacillus thuringiensis and Its. . .
413
bands in SDS-PAGE was correlated with the molecular weight of dipteran active
proteins. Based on this comparison, several protein profiles corresponded to the
specific Cry or Cyt proteins toxic for dipterans (molecular masses of 17–28 kDa
correspond to Cry17 and Cyt, 50 kDa to Cry2Ab, 65–75 kDa to Cry2Aa, Cry2Ac,
Cry4D, Cry17A, Cry19 and Cry24, 80 kDa to Cry4C and Cry11B, and 128–140 kDa
correspond to Cry4A, Cry4B, Cry32). The protein profile analysis revealed a great
diversity of protein patterns within the Iranian Bt collections.
10.8.5 Biological Activity
All the mentioned means of characterization; parasporal crystal morphology, biochemical experiments, PCR-screening and SDS-PAGE analysis, are being used to
predict the insecticidal activity of newly isolated Bt strains. Therefore, performing
bioassays provides complementary information on the biological activity of the
isolated Bt strains. Moreover, the final goal of these studies is to introduce a highly
potent and effective Bt strain for biological pest control. Therefore, many studies
were carried out to evaluate the insecticidal activity of Iranian Bt strains or Iranian
commercial Bt-based products.
The bioassays with the Bt strains harboring genes encoding proteins active for
lepidopterans were carried out against the cotton bollworm, Helicoverpa armigera
Hüber (Lep.: Noctuidae). Several strains with high insecticidal activity have been
introduced as good candidates for biocontrol of this pest (Seifinejad et al. 2008). The
Bt strains containing coleopteran-active cry genes, were bioassayed against the elm
leaf beetle, X. luteola first instar larvae (Nazarian et al. 2009), leading to the
identification of novel cry genes based on the PCR analysis and also the introduction
of potent Iranian Bt strains for biological control of coleopteran insect pests,
particularly X. luteola. With the aim of finding the nematicidal Bt strain, 70 Bt
isolates available in the Bt collection of Agricultural Biotechnology Research
Institute of Iran (ABRII) were characterized. Based on the presence of the cry
genes active against nematodes, the nematicidal activity of these Bt strains against
Meliodogyne incognita, Chiloplacus tenuis and Acrobeloides enoplus were evaluated (Salehi Jouzani et al. 2008c). Based on the bioassays, two strains YD5 and
KON4 were toxic to M. incognita, and two studied free-living nematodes, C. tenuis
and A. enoplus, were susceptible to strains SN1 and KON4 (Salehi Jouzani et al.
2008c).
In several cases, the screening and characterization studies led to the introduction
of potent Bt strains to industrial sections for mass production. The Iranian strains
isolated from soil and infected larvae were thoroughly characterized (Khorramnejad
et al. 2018). Bt strains with diverse larvicidal activity against Indian meal moth,
P. interpunctella, were selected and characterized by employing different techniques. The insecticidal activity of selected Bt strains was investigated against
different lepidopteran pest species; Spodoptera exigua, Mamestra brassicae,
10 Progress on the Bacterium Bacillus thuringiensis and Its. . .
413