Differences of growth and root absorption of different apple rootstock seedlings in replant stress

【Objective】 Selecting appropriate rootstocks is one of the most effective methods of preventing apple from replant disease. In order to provide theoretic foundation for screening of anti-replant rootstock materials and breeding anti-replant rootstock varieties, differences of growth and root absorption of three apple rootstock seedlings were compared, and absorption of potassium and calcium ions under the replant stress was discussed in this study.【Methods】 One-year-old seedlings of Malus hupehensis Rehd, Malus sieversii(Ledeb.) Roem and Malus prunifolia(Willd.) Borkh were used as the materials, and 0-40 cm rhizosphere soil of 20 years' orchard which ‘Fuji' apple on M . robusta stock located in Tai'an city was used as matrix. The seedlings were divided into two parts, some of the seedlings were supplied to determine the flow velocity of rhizosphere K+ and Ca2+ under the replant stress by Non-invasive Micro-test Technique on April 25, 2012, other seedlings were transplanted into pots of 25 cm wide and 30 cm deep. The height, stem diameter, chlorophyll content and photosynthetic rate of the seedlings were investigated from July to September. The root structure was scanned and dry weight and fresh weight of roots, branches and leaves were measured respectively after the growing season. 【Results】The aboveground growth of the three rootstocks is suppressed in different levels under the replant stress. The heights of M. hupehensis have no significant differences before and after the replant stress, while the heights of the other two rootstocks are significantly decreased. The photosynthetic rates have no significant decreases except M. Sieversii. The chlorophyll contents of three rootstocks are significantly decreased and there are no obviously changes in stem diameter. The dry matter of M. sieversii seedlings is significantly decreased under the replant stress, while the root-shoot ratio is increased. Root biomass amounts of the three rootstocks are increased observably and the total root lengths are increased to 1.45 times, 2.22 times, 1.71 times, respectively compared to the control. Root activities of the three rootstocks are all decreased, which the one of M. hupehensis fell less than those of the other two rootstocks. The flow velocity of K+ changes from inward to outward under the replant stress and has a little change for M. hupehensis, in contrast, there is significant change in the average ion flow rate of K+ for M. sieversii. The velocity direction of Ca2+ has no change for M. hupehensis, and the velocity direction of Ca2+of the other two rootstocks changes into outward from inward, and the most significant change in the flow velocity of Ca2+ appears in M. sieversii.【Conclusion】The shoot growth of apple rootstocks is significantly inhibited and the amounts of roots are increased. The absorption of K+ and Ca2+ affected by different degree. As the less tolerant rootstocks, M. Sieversii's dry matter accumulation is seriously constrained and the root-shoot ratio is significantly increased, and the absorptions of K+ and Ca2+ was also severely affected. M. hupehensis has a stronger resistance, its root-shoot ratio was relatively stable, as well as the absorptions of K+ and Ca2+are affected minimally. The performance of M. prunifolia is in middle.