Preselection For Iron Deficiency Tolerance And Dwarfing In Apple Rootstock

Iron is one of the essential micronutrients required by all living organisms. Iron deficiency chlorosis is very serious on calcareous soils. The problem is particularly serious in apples grown on high pH soils in North China. One of the best solutions for Fe deficiency stress lies in the use of tolerant rootstocks to prevent chlorosis. Making use of the dwarfing rootstocks is an important technical measure for the dense-planting cultivation of the fruit trees. A lot of dwarf rootstocks have been introduced to our country, but many of them have poor adaptation to the environment and have high requirements in fertilizer and water. Therefore, cultivating excellent comprehensive properties of dwarf rootstock become urgent needs for the apple production of China. However, the selection of rootstocks based on field trials is very time and labor consuming. An efficient molecular selection approach has been badly needed to improve breeding efficiency.141true-hybrids were obtained derived from a cross between M. xiaojinensis and M. baccata as experiment material, from using dot-blot macroarray, the expression levels of MxHA7, MxFIT1,MxIRT1, MsxCS1and MxRD3in young roots of141interspecific hybrids were analyzed. The results showed that:(1) A reverse northern blot-based dot-blot macroarray protocol was established in this paper.(2) Iron deficiency tolerance is inherited as a typical quantitative trait.(3) Under low iron conditions, the expression of the five genes in the hybrids was negatively correlated with IDCI.(4) According to the gene expression markers,14hybrid lines were preselected and only two hybrids did not meet the IDCI criterion and a high percentage (85.7%) of preselections by MAS were validated by the phenotypic criterion. In order to get the dwarf rootstocks, the experiment materials M. xiaojinensis x M9hybrid lines and M. robusta Rehds x M9hybrid lines were preselected by using gene expression marker. Expression levels of MdPIN8and MdPIN10genes in stem phloem and MdlPTs in young root were detected by dot-blot macroarray. The results showed that:(1) The frequency distributions of gene expression for MdPIN8and MdPIN10segregating among the hybrid population showed approximately Gaussian distributions, and the expression levels in the hybrids was correlated with IAA content in stem phloem.(2) The frequency distributions of gene expression for MdIPTs segregating among the hybrid population showed a normal distribution, and the expression levels in the hybrids was correlated with ZT content in root.(3) According to MdPIN8and MdPIN10expression markers,6and41lines for dwarfing ability as interstock were respectively selected in M. xiaojinensis×M9hybrid lines and M. robusta Rehds x M9hybrid lines.(4) Using the MdIPTs expression marker,8and68lines for dwarfing ability as rootstock were preliminarily selected respectively in two progenies.