Павел

->add('item', 'entity', array(
    'class' => 'AcmeHelloBundle:Item',
    'property' => 'title',
));

$builder->add('item', 'entity', array(
    'class' => 'AcmeHelloBundle:Item',
    'query_builder' => function(EntityRepository $er) {
        return $er->createQueryBuilder('u')
            ->orderBy('u.username', 'ASC');
    },
));