Polymerase chain reaction screening of Bt isolates for a panel of Cry, Cyt and PS genes. PCR reactions were conducted as described in Materials and Methods section. Amplicons were run at 100 v for 30 min in 2% agarose gels pre-stained with ethidium bromide and examined with a charge-coupled device (CCD) camera mounted on a UVITC gel documentation system. Standard DNA marker was included in lane 1 to identify band sizes. (A) PCR of four Cry (4A, 4B, 10 and 11) Cyt (1 and 2) genes. All nine Bt strains were negative for these genes except the reference strain Bacillus thuringiensis subsp. israelensis (Bti-H14), which were positive for all tested Cry and Cty genes. (B) PCR for parasporin genes PS1, PS2, PS3 and PS4. All nine strains were positive for PS1 but negative for the rest. Neg., denotes negative control lane where deionized water was included instead of plasmid DNA template.