Effects Of Different Dwarfing Interstocks On Organic Acid Contents And Metabolizing Enzyme Activities Of ‘Red Fuji’ Apple

Organic acid was one of the important indicators of fruit quality, and malic acid was the dominant organic acid in apple. At home and abroad a lot of researches had been carried out in the effects of rootstocks on fruit quality, but this study on the effect of rootstocks on apple fruit organic acid metabolism was limited. In this research, Red Fuji apple grafted on different hybrid progeny were used to study the effects of sexual progenies of different rootstocks on malic acid content in ripe fruits, and the effects of different SH40 seeding inter-stocks on organic acid content and their relatied enzyme activities of Fuji apple were studied, further through the real-time PCR technology was used to detect gene expressions of mainly enzymes of malic acid metabolism.Main results as following:1. The malic acid contents of Red Fuji apple grafted on hybrid progeny of Malus micromalus × Malus zumi, M. Micromalus × P22 and M. Micromalus × S19 and seedling progeny of Malus robusta Rehd were analyzed, there is the highest malic acid content in the apple fruit grafted on hybrid progeny of Malus micromalus ×Malus zumi. The malic acid content in the apple fruit grafted on seedling progeny of Malus robusta Rehd was the lowest. There was greater separation on acid content in Red Fuji apple grafted on different hybridized combinations.2. The organic acid contents of apple in developing fruits were examined, ‘Red Fuji’ apple trees grafted on three interstocks No.53, No.111 and No.236, which were chose from SH40 seeding inter-stocks. The results showed that the concentration of titratable acid contents gradually increased during fruit development and peaked 30 days after bloom then declined. The titratable acid contents in ripe apple on No.53 seedling inter-stocks showed higher than that of No.111. The malic acid content, citric acid content, fumaric acid content and titratable acid content had the similar trend of different treatments; At 160 days after bloom, the malic acid contents in Fuji apple on No.53 seedling inter-stocks showed higher than that of No.111, the citric acid content and fumaric acid content were higher than that of No.111 and No.236. The succinic acid content in different treatments were all accumulated gradually at 20 days after bloom, and there was strong negative correlation between with the contents of succinic acid and titratable acid; The succinic acid contents in ripe fruits were no significant difference between treatments.3. During fruit development, there was a negative correlation between NADP-ME activities and malic acid contents in fruit. The NAD-MDH activities in Fuji apple on No.53 seedling inter-stocks showed higher than that of No.111 from 20 to 30 daysafter bloom and before the fruits riping. The NADP-ME activities in Fuji apple on No.111 seedling inter-stocks showed higher than that of No.53 from 70 and 100 days after bloom. There was a positive correlation between PEPC activities and malic acid contents in fruit, while which was not mainly affected the difference in the accumulation of malic acid contents.The citric acid contents in fruit on No.53 seedling inter-stocks was the highest from 70 to 130 days after bloom, the NAD-IDH activities in Fuji apple on No.53 seedling inter-stocks was the highest, but the Mit-ACO activities was the lowest; The Cyt-ACO activities in Fuji apple on No.53 seedling inter-stocks showed higher than others from 100 to160 days after bloom. The NAD-IDH activities Mit-ACO activities and Cyt-ACO activities lead the citric acid contents in nature fruit had differences among the treatments. there was a positive correlation between CS activities and citric acid contents in fruit, while the CS activities were not mainly affected the difference in the accumulation of citric acid contents.4. The relative expression of NAD-MDH genes in fruit on No.53 seedling inter-stocks showed higher than that of No.236 at 100 days after bloom, but the relative expression of NADP-ME genes in fruit on No.236 seedling inter-stocks showed lower then that of No.53; At 160 days after bloom, the relative expression of NAD-MDH genes in fruit on No.53 seedling inter-stocks showed higher than the highest, and the relative expression of NADP-ME genes showed lower than that of No.236.