Abstract:

In order to study the metabolism mechanism of malic aicd in apples on different interstocks，‘Red Fuji’apple trees grafted on three interstocks No.53，No.111 and No.236 were used as materials in this experiment，which were chosen from SH40 seedlings. The contents of malic acid，the enzymes activities and the expression of genes related to malic acid metabolism were analyzed during the fruit development. The results showed that the malic acid content in the ripe fruits on No.53 inter-stocks was higher than that of No.111. The NAD-MDH activities in Fuji apple on No.53 inter-stocks were higher than that of No.111 in the 30，40，100 and 160 day after full bloom，the PEPC activities in Fuji apple on No.53 inter-stocks were higher than that of No.111 in the 30 and 130 day after full bloom，and the NADP-ME activities in Fuji apple on No.111 inter-stocks was higher than that of No.53 in the 100 day after full bloom. The relative expression of NAD-MDH gene and NADP-ME gene in fruit on No.53 inter-stockswere higher than that of No.111 in the 100 day and 160 day after bloom. The relative expression of PEPC gene in fruit on No.53 inter-stock showed higher than that of No.111 in the 30 day and 160 day after full bloom. It was concluded that different interstocks influnced expression of genes related to malic acid synthesis and degradation firstly，then related enzymes activities would be regulated，and at last resulted in different malic acid contents in apple on different-inter stocks.

Key words: Malus ×, domestica, inter-stocks, malic acid, NAD-MDH, real-time PCR