Overexpression of Chitinase gene enhances resistance to Colletotrichum gloeosporioides and Alternaria alternata in apple (Malus×domestica)

Abstract Apple is a cultivated fruit tree, worldwide. However, the growth and development of apple have been increasingly affected by fungal disease. Chitinase is one of the most important defensive proteins in plant. Their biological function and disease resistance mechanism, including apple, is rarely reported. In our previous study, we found that autotetraploid 'Hanfu' apple is more resistant to fungal disease than diploid apple. In addition, RNA sequencing (RNA-seq) analysis revealed that the expression level of the MdCHI1 gene was significantly up-regulated in the autotetraploid apple. In this work, we isolated CHI1 from 'Hanfu' apple, and the quantitative real-time PCR (qRT-PCR) analyses demonstrated that MdCHI1 was highly expressed in leaves of apple and was rapidly induced by MeJA. Then, we obtained 4 lines of MdCHI1-OE by Agrobacterium-mediated transformation method. The MdCHI1-OE plants were more resistant to fungal diseases caused by Colletotrichum gloeosporioides and Alternaria alternata, moreover the chitinase activity in MdCHI1-OE plants was greater than that of 'GL-3′ (WT) plants. Taken together, the data provide insights that MdCHI1 as an important role in the fungal disease resistance of apple.