functions.php

<?php

/**
 * Primary Menu using custom Walker
 * 
 * Copieid the contents of genesis_do_nav() in /genesis/lib/structure/menu.php, then changed args
 */
function be_primary_menu() {
 
 	//* Do nothing if menu not supported
	if ( ! genesis_nav_menu_supported( 'primary' ) )
		return;

	//* If menu is assigned to theme location, output
	if ( has_nav_menu( 'primary' ) ) {

		$class = 'menu genesis-nav-menu menu-primary';
		if ( genesis_superfish_enabled() )
			$class .= ' js-superfish';

		$args = array(
			'theme_location' => 'primary',
			'container'      => '',
			'menu_class'     => $class,
			'echo'           => 0,
			'walker'         => new Walker_Nav_Menu_Dropdown(),
		);

		$nav = wp_nav_menu( $args );

		//* Do nothing if there is nothing to show
		if ( ! $nav )
			return;

		$nav_markup_open = genesis_markup( array(
			'html5'   => '<nav %s>',
			'xhtml'   => '<div id="nav">',
			'context' => 'nav-primary',
			'echo'    => false,
		) );
		$nav_markup_open .= genesis_structural_wrap( 'menu-primary', 'open', 0 );

		$nav_markup_close  = genesis_structural_wrap( 'menu-primary', 'close', 0 );
		$nav_markup_close .= genesis_html5() ? '</nav>' : '</div>';

		$nav_output = $nav_markup_open . $nav . $nav_markup_close;

		echo apply_filters( 'genesis_do_nav', $nav_output, $nav, $args );

	}


}
add_action( 'genesis_after_header', 'be_primary_menu' );
remove_action( 'genesis_after_header', 'genesis_do_nav' );