bipyramidal crystals and a relationship between crystal protein production and the
geographical origin of Bt strains was found (Moazamian et al. 2016).
Altogether, the results of the screening program, whether on a vast or small scale,
showed that Bt was predominantly isolated from diverse ecological habitats in
different geographical regions of Iran. The high abundance of Bt isolates in the
samples points to the richness of the selected habitats, which consequently led to the
building of several local Bt collections.
10.8 Characterization
The characterization of novel Bt strains may lead to the identification of effective and
highly potential Bt strains for application in the biological control of pests. The
characterization of Bt strains is performed by different methods. The morphological
characterization is initially carried out to somehow reflect the possible insecticidal
activity of the Bt strains (Lecadet et al. 1999). Biochemical experiments (Martin
et al. 1985) are used to identify the biochemical types of Bt strains. PCR-based
characterization is utilized as a rapid means of Bt gene identification and prediction
of insecticidal activity (Carozzi et al. 1991; Juárez-Pérez et al. 1997). Afterward, the
expression of the detected genes in PCR is initially investigated by SDS-PAGE
analysis, and subsequently, the protein composition can be detected by LC-MS/MS
analysis. As the most important step of characterization, the biological activity of Bt
strains against susceptible targets, from insect orders, mites, nematodes or even plant
pathogens, has to be evaluated. Recently, the characterization of the insecticidal
activity spectrum of Bt strains is performed following the in vitro toxicity assays
using the insect cultured cell lines (Smagghe et al. 2009; Soberón et al. 2018).
Indeed, insect cell lines have been considered as an easy, rapid and accurate
technique for studying the spectra activity of Bt toxins and their mode of action.
The Iranian Bt collections have undergone different means of characterization in
order to describe the local Bt strains and determine their biological activity. The most
commonly used methods for characterization of Bt strains in Iran are
mentioned here.
10.8.1 Crystal Morphology
B. thuringiensis isolates are characterized based on the presence of parasporal
inclusions in the sporangium of the sporulating cell (de Maagd et al. 2001). Microscopic observations (Fig. 10.3) were performed in several Iranian laboratories to
detect the Bt isolates based on the presence of parasporal inclusions and to study the
Bt crystal morphology as the initial description of newly isolated Bt strains (Salehi
Jouzani et al. 2008b; Keshavarzi 2008; Seifinejad et al. 2008; Nazarian et al. 2009).
The majority of Bt strains isolated by Salehi Jouzani et al. (2008b) produced the
410
A. Khorramnejad et al.
geographical origin of Bt strains was found (Moazamian et al. 2016).
Altogether, the results of the screening program, whether on a vast or small scale,
showed that Bt was predominantly isolated from diverse ecological habitats in
different geographical regions of Iran. The high abundance of Bt isolates in the
samples points to the richness of the selected habitats, which consequently led to the
building of several local Bt collections.
10.8 Characterization
The characterization of novel Bt strains may lead to the identification of effective and
highly potential Bt strains for application in the biological control of pests. The
characterization of Bt strains is performed by different methods. The morphological
characterization is initially carried out to somehow reflect the possible insecticidal
activity of the Bt strains (Lecadet et al. 1999). Biochemical experiments (Martin
et al. 1985) are used to identify the biochemical types of Bt strains. PCR-based
characterization is utilized as a rapid means of Bt gene identification and prediction
of insecticidal activity (Carozzi et al. 1991; Juárez-Pérez et al. 1997). Afterward, the
expression of the detected genes in PCR is initially investigated by SDS-PAGE
analysis, and subsequently, the protein composition can be detected by LC-MS/MS
analysis. As the most important step of characterization, the biological activity of Bt
strains against susceptible targets, from insect orders, mites, nematodes or even plant
pathogens, has to be evaluated. Recently, the characterization of the insecticidal
activity spectrum of Bt strains is performed following the in vitro toxicity assays
using the insect cultured cell lines (Smagghe et al. 2009; Soberón et al. 2018).
Indeed, insect cell lines have been considered as an easy, rapid and accurate
technique for studying the spectra activity of Bt toxins and their mode of action.
The Iranian Bt collections have undergone different means of characterization in
order to describe the local Bt strains and determine their biological activity. The most
commonly used methods for characterization of Bt strains in Iran are
mentioned here.
10.8.1 Crystal Morphology
B. thuringiensis isolates are characterized based on the presence of parasporal
inclusions in the sporangium of the sporulating cell (de Maagd et al. 2001). Microscopic observations (Fig. 10.3) were performed in several Iranian laboratories to
detect the Bt isolates based on the presence of parasporal inclusions and to study the
Bt crystal morphology as the initial description of newly isolated Bt strains (Salehi
Jouzani et al. 2008b; Keshavarzi 2008; Seifinejad et al. 2008; Nazarian et al. 2009).
The majority of Bt strains isolated by Salehi Jouzani et al. (2008b) produced the
410
A. Khorramnejad et al.