Abstract: Bacillus megaterium Ap25 which can produce endoglucanase was proved as a biocontrol agent of plant disease. The aim of this study is to enhance the biocontrol effect of this strain by introduction of a chitinase gene. A 1. 8 kb DNA fragment containing chitinase gene and SD sequence was amplified with the template pMSDChi113 and was inserted into shuttle vector pHY300PLK to construct a new plasmid, pHYChi113. The recombinant plasmid was transformed into B. megterium, resulting in a new strain named Ap25-chi113. Chitin plate culture and PCR amplification confirmed that Ap25-chi113 contained a functional chitinase gene . Comparing with the wild type Ap25 in dural culture experiment , Ap25- chi113 increased its effect against the pathogenic fungi. Especially, the inhibition percentage against Coniothyrium fuckellii increased about 13%. In pot experiment , Ap25- chi113 also increased the effect on suppression of wheat sheath blight and cotton Fusarium wilt caused by Rhizotonia cerealis and Fusarium oxysporum respectively, comparing with the wild strain.

Key words: Chitinase