asp:Treeview expand/Collase too slow in UpdatePanel

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ASP.NET

Javascript

jQuery

C#3.5

my tree view having 1000 nodes when click on expand/collapse it take around 20 sec to expand/collapse
how i can improve tree view performance, keeping EnableClientScript='false'

<cc1:ToolkitScriptManager ID="tkScriptMgr"  runat="server">
</cc1:ToolkitScriptManager>
<asp:UpdatePanel ID="UPanel1" runat="server" UpdateMode="Always">
    <ContentTemplate>
        <table width="100%">
            <tr>
                <td>
                    <asp:TreeView ID="tvDtdHierarchy" runat="server" ShowLines="True" TabIndex="-1" EnableClientScript="false"
                        OnInit="tvDtdHierarchy_Init" OnLoad="tvDtdHierarchy_Load"
                        OnPreRender="tvDtdHierarchy_PreRender" OnTreeNodePopulate="tvDtdHierarchy_TreeNodePopulate"
                        OnDataBound="tvDtdHierarchy_DataBound"
                        Target="_Self">
                        <ParentNodeStyle Font-Bold="False" />
                        <HoverNodeStyle Font-Underline="True" ForeColor="#DD5555" />
                        <NodeStyle Font-Names="Tahoma" Font-Size="10pt" ForeColor="Black" HorizontalPadding="0px"
                            NodeSpacing="0px" VerticalPadding="0px" />
                    </asp:TreeView>
                </td>
            </tr>
        </table>
    </ContentTemplate>
</asp:UpdatePanel>