| The utilization of dwarfing self-rooted rootstock seedlings is the development direction of apple industry in china. SH series are the main apple dwarf rootstock in North China and Northwest China because of their good performance on cultivation. The promotion and application in large area has been limited because of its low rooting rate on the propagation process. It is used as interstock currently. In order to achieve the production and application of self-rooted rootstocks, it’s necessary to establish an efficient and rapid propagation system of apple dwarfing rootstocks cutting. In the study, taking annual SH40 whose root-stock is Malus robusta as materials to obtain cutting shoots. The effects of seedling quality, intercept length, bud-notching on the amount of shoot and etiolation treatment on rooting rate of cutting shoots were researched. And morphological and anatomical structure, the contents of starch, soluble sugar, soluble protein and the expression of rooting related genes on the shoots cutting process were studied. Designed to reveal the mechanism of etiolation treatment on promoting cuttings rooting, and optimize the softwood cutting propagation technique of SH40. The main results were as follows:1. The amount of shoots can be improved by choosing high quality seedlings, cutting the seedlings appropriately and carving the bud. The SH40 seedlings with about 0.5 cm in diameter whose average shoot amount of individual plant is 3.4. The SH40 seedlings with about 1 cm in diameter whose average shoot amount of individual plant is 8.3, whose average shoot amount of individual plant is 2.4 times higher than those with about 0.5 cm in diameter. When the bud is sufficient, the shorter of the truncated seedlings, the higher of the average shoot amount. Simultaneously, the buds germinate early and intensively. The intercept length of SH40 seedlings are 25, 35, 45, 60 cm whose average shoot amount of individual plant of are 5.73, 5.55, 4.76 and 4.4 respectively. The seedlings with budnotching whose average shoot amount of individual plant is 10.5, otherwise is 8.3. The seedlings with bud-notching whose average shoot amount of individual plant is 26.51% higher than those without bud-notching.2. The rooting rate of cutting shoots was improved significantly, the number of adventitious roots and the average root length were increased, and the rooting cycle was reduced after basal etiolation. After shoot basal etiolated, cuttings rooting rate is as high as 92.31%, the average number of adventitious roots is 14, and the average root length is 29.30 mm. The control group is 51.92%, the average number of adventitious roots is 7, and the average root length is 19.13 mm. while, the cutting rooting rate of complete etiolated shoots is only 17.95%, the average number of adventitious roots is 17, and the average root length is 26.51 mm, others died gradually 12 days later after cutting. The basal etiolation treatment can reduce the formation of callus on the base of shoots. After basal etiolatied, the shoots have begun to root within12 days after cuttage, which is 3-5 days earlier than the compared shoots.3. The basal etiolation treatment changed the proportion of stem pith, xylem, phloem(include cambium) and the cortex in the base of shoots. After shoot basal etiolated, the proportion of stem pith, xylem, phloem(include cambium) and the cortex is 1:0.73:0.41:1.21, otherwise is 1:0.86:0.43:0.73. they have significantly difference on cortex.4. The root primordia may occur in the phloem, cortex and pith ray in the cutting rooting process of SH40 shoots.5. The expression of gene ARRO-1 and ARF7 have been improved after basal etiolation treatment. The relative expression of ARRO-1, ARF7 and ARF19 genes were respectively 14.37, 2.11 and 1.75 times higher than the control at the cutting day. The relative expression of ARRO-1 gene was significantly increased after make them quick dipping in IBA solution. the relative expression was 60.84 time higher than the comparison and reached the peak at the second day after cutting. However, the relative expression of ARF7 and ARF19 gene was not increased too much, was respectively 2.84 and 2.41 times of the control. This study showed that the ARRO-1 gene might be the major gene involved in the formation of SH40 shoots adventitious roots. The relative expression of ARRO-1 gene of non-etiolated shoots is 49.54 times of the control at the cutting day, but the relative expression of ARF7 and ARF19 genes were decreased. Meanwhile the basal etiolation treatment increased the contents of starch and soluble sugar in the base of stem, which is beneficial to the formation and differentiation of root primordia, as well as promotes shoots cutting rooting. |
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