DETERMINATION AND DISTRIBUTION OF CRY-TYPE GENES OF BACILLUS-THURINGIENSIS ISOLATES FROM TAIWAN

Using PCR with a set of specific oligonucleotide primers to detect cry I-type genes, we were able to screen the cry-type genes of 225 Bacillu s thuringiensis soil isolates from Taiwan without much cost in time or labor. Some combinations of cry genes (the cry-type profile) in g sin gle isolate were unique. We identified five distinct profiles of cryst al genes from the B. thuringiensis soil isolates from Taiwan. The cry genes included cryIA(a), cryIA(b), cryIA(c), cryIC, cryID, and cryIV. Interestingly, 501 B. thuringiensis isolates (93.5% of the total numbe r that we identified) were isolated from areas at high altitudes. The profiles of cry-type genes were distinct in all isolation areas. The d istribution of cry-type genes of our isolates therefore depended on ge ography. Using PCR footprinting to detect cryIC-type genes, we identif ied two distinct cryIC footprints from some of our isolates, indicatin g that these isolates may contain novel cryIC-type genes. B. thuringie nsis isolates containing cryIA(a)-, cryIA(b)-, and cryIA(c)-type genes exhibited much greater activity against Plutella xylostella than did other isolates, indicating that multiple cry type genes may be used as markers for the prediction of insecticidal activities.