How to remove margin between MenuItem controls WPF - wpf

Question

I have custom style for my menu control and my menu item controls that are based on generic wpf style.My problem is that I can't figure out how to remove thin margin line between MenuItem Controls.
As you can see there is a thin white margin line between my menuItem which has bg set to black and gray border.
Here's my entire xaml code for MenuItem style:
<Style x:Key="macMenuItemStyle" TargetType="{x:Type MenuItem}">
<Setter Property="Foreground"
Value="{Binding Path=Foreground,
RelativeSource={RelativeSource AncestorType={x:Type Menu}}}"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type MenuItem}">
<Border x:Name="Border" Background="Black"
BorderBrush="{TemplateBinding BorderBrush}"
BorderThickness="{TemplateBinding BorderThickness}">
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition x:Name="Col0" MinWidth="17" Width="Auto"
SharedSizeGroup="MenuItemIconColumnGroup"/>
<ColumnDefinition Width="Auto"
SharedSizeGroup="MenuTextColumnGroup"/>
<ColumnDefinition Width="Auto"
SharedSizeGroup="MenuItemIGTColumnGroup"/>
<ColumnDefinition x:Name="Col3" Width="14"/>
</Grid.ColumnDefinitions>
<!-- ContentPresenter to show an Icon if needed -->
<ContentPresenter Grid.Column="0" x:Name="Icon"
Margin="4,0,6,0"
VerticalAlignment="Center"
ContentSource="Icon"/>
<!-- Glyph is a checkmark if needed for a checkable menu -->
<Grid Grid.Column="0" x:Name="GlyphPanel"
Visibility="Hidden"
Margin="4,0,6,0"
VerticalAlignment="Center">
<Path x:Name="GlyphPanelpath"
VerticalAlignment="Center"
Fill="{TemplateBinding Foreground}"
Data="M0,2 L0,4.8 L2.5,7.4 L7.1,2.8 L7.1,0 L2.5,4.6 z"
FlowDirection="LeftToRight"/>
</Grid>
<!-- Content for the menu text etc -->
<ContentPresenter Grid.Column="1" x:Name="HeaderHost"
Margin="{TemplateBinding Padding}"
RecognizesAccessKey="True"
ContentSource="Header"/>
<!-- Content for the menu IGT -->
<ContentPresenter Grid.Column="2" x:Name="IGTHost"
Margin="8,0,8,0"
ContentSource="InputGestureText"
VerticalAlignment="Center"/>
<!-- Arrow drawn path which points to the next level of the menu -->
<Grid Grid.Column="3" x:Name="ArrowPanel"
Margin="4,0,6,0" VerticalAlignment="Center">
<Path x:Name="ArrowPanelPath"
HorizontalAlignment="Right"
VerticalAlignment="Center"
Fill="{TemplateBinding Foreground}"
Data="M0,0 L0,8 L4,4 z"/>
</Grid>
<!-- The Popup is the body of the menu which expands down
or across depending on the level of the item -->
<Popup x:Name="SubMenuPopup"
IsOpen="{Binding Path=IsSubmenuOpen, RelativeSource={RelativeSource TemplatedParent}}"
Placement="Right"
Focusable="false"
AllowsTransparency="True"
PopupAnimation="{DynamicResource {x:Static SystemParameters.MenuPopupAnimationKey}}">
<Border x:Name="SubMenuBorder"
Margin="0,0,8,8" CornerRadius="0,0,3,3"
Padding="0" Background="#FDFCFC"
BorderBrush="#DCD5D6" BorderThickness="1">
<Grid x:Name="SubMenu" Grid.IsSharedSizeScope="True">
<!-- StackPanel holds children of the menu. This is set by IsItemsHost=True -->
<StackPanel IsItemsHost="True" KeyboardNavigation.DirectionalNavigation="Cycle"/>
</Grid>
<Border.Effect>
<DropShadowEffect BlurRadius="5" ShadowDepth="1.5" Opacity="0.1"/>
</Border.Effect>
</Border>
</Popup>
</Grid>
</Border>
<!-- These triggers re-configure the four arrangements of MenuItem
to show different levels of menu via Role -->
<ControlTemplate.Triggers>
<!-- Role = TopLevelHeader : this is the root menu item in a menu;
the Popup expands down -->
<Trigger Property="Role" Value="TopLevelHeader">
<Setter Property="Padding" Value="6,0,6,0"/>
<Setter Property="Placement" Value="Bottom" TargetName="SubMenuPopup"/>
<Setter Property="MinWidth" Value="0" TargetName="Col0"/>
<Setter Property="Width" Value="Auto" TargetName="Col3"/>
<Setter Property="Visibility" Value="Collapsed" TargetName="Icon"/>
<Setter Property="Visibility" Value="Collapsed" TargetName="GlyphPanel"/>
<Setter Property="Visibility" Value="Collapsed" TargetName="IGTHost"/>
<Setter Property="Visibility" Value="Collapsed" TargetName="ArrowPanel"/>
</Trigger>
<!-- Role = TopLevelItem: this is a child menu item
from the top level without any child items-->
<Trigger Property="Role" Value="TopLevelItem">
<Setter Property="Padding" Value="6,1,6,1"/>
<Setter Property="Visibility" Value="Collapsed" TargetName="ArrowPanel"/>
</Trigger>
<!-- Role = SubMenuHeader : this is a child menu item
which does not have children -->
<Trigger Property="Role" Value="SubmenuHeader">
<Setter Property="DockPanel.Dock" Value="Top"/>
<Setter Property="Padding" Value="6,1,6,1"/>
</Trigger>
<!-- Role = SubMenuItem : this is a child menu item which has children-->
<Trigger Property="Role" Value="SubmenuItem">
<Setter Property="DockPanel.Dock" Value="Top"/>
<Setter Property="Padding" Value="0,0,0,0"/>
<Setter Property="Visibility" Value="Collapsed" TargetName="ArrowPanel"/>
</Trigger>
<Trigger Property="IsSuspendingPopupAnimation" Value="true">
<Setter Property="PopupAnimation" Value="None" TargetName="SubMenuPopup"/>
</Trigger>
<!-- If no Icon is present the we collapse the Icon Content -->
<Trigger Property="Icon" Value="{x:Null}">
<Setter Property="Visibility" Value="Collapsed" TargetName="Icon"/>
</Trigger>
<!-- The GlyphPanel contains the CheckMark -->
<Trigger Property="IsChecked" Value="true">
<Setter Property="Visibility" Value="Visible" TargetName="GlyphPanel"/>
<Setter Property="Visibility" Value="Collapsed" TargetName="Icon"/>
</Trigger>
<!-- Using the system colors for the Menu Highlight and IsEnabled-->
<Trigger Property="IsHighlighted" Value="true">
<Setter Property="Background" Value="{StaticResource macHighlightItemBrush}" TargetName="Border"/>
<Setter Property="Foreground" Value="White"/>
</Trigger>
<Trigger Property="IsEnabled" Value="false">
<Setter Property="Foreground" Value="LightGray"/>
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
Here's my menu custom style:
<Style x:Key="macMenuStyle" TargetType="{x:Type Menu}">
<Setter Property="Background" Value="{StaticResource macMenuBrush}"/>
<Setter Property="FontFamily" Value="{DynamicResource {x:Static SystemFonts.MenuFontFamilyKey}}"/>
<Setter Property="FontSize" Value="{DynamicResource {x:Static SystemFonts.MenuFontSizeKey}}"/>
<Setter Property="FontStyle" Value="{DynamicResource {x:Static SystemFonts.MenuFontStyleKey}}"/>
<Setter Property="FontWeight" Value="{DynamicResource {x:Static SystemFonts.MenuFontWeightKey}}"/>
<Setter Property="Foreground" Value="#FF212121"/>
<Setter Property="VerticalContentAlignment" Value="Center"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type Menu}">
<Border BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" Padding="{TemplateBinding Padding}" SnapsToDevicePixels="True">
<ItemsPresenter SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"/>
</Border>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>