Chitinase CHIT36 from Trichoderma harzianum Enhances Resistance of Transgenic Carrot to Fungal Pathogens

摘要

Microbial endochitinase CHIT36 is one of the lytic enzymes secreted by Trichoderma harzianum that exhibits antifungal activity in vitro. To evaluate its activity when expressed in planta, a plasmid containing chit36 gene under the control of CaMV 35S promoter and the nptII selection gene were introduced into polyethylene glycol (PEG)-treated carrot (Daucus carota L.) protoplasts. The transgenic plants expressing CHIT36 were used in resistance assays to evaluate their susceptibility to fungal pathogens. Laboratory-based assays on detached leaves and petioles showed that the transgenic carrots had less severe disease symptoms. The resistance response depended on the transgenic clone, but all clones had significantly enhanced tolerance to Alternaria radicina and Botrytis cinerea, on average by 50%. Slower disease progress caused by Alternaria dauci was observed for two transgenic clones while the remaining clone was more susceptible than the control. The most resistant transgenic clones were also more tolerant to the pathogens than 'Bolero' F, which is a conventionally bred cultivar tolerant to A. dauci. This is the first report of the use of microbial chitinase to enhance carrot resistance. The results indicate that CHIT36 expressed in planta has the potential to reduce development of fungal diseases.