In your navbar template (styles and templates > style manager > edit templates > navigation/breadcrumb templates > navbar)
Find:
HTML Code:
<td class="vbmenu_control"><a href="memberlist.php$session[sessionurl_q]">$vbphrase[members_list]</a></td>
Replace With
HTML Code:
<td class="vbmenu_control"><a href="strainsdb.php">$vbphrase[strain_guide]</a></td>
Add phrase
Type: GLOBAL
Product: vBulletin
VarName: strain_guide
Text: Strain Guide