Ember: recover data from dynamic "select" tags

Using Ember, I am trying to build a form, with <select> droplists populated from stores. I don't know how to recover a value from here to use in a "save" function.

What am I doing wrong?

Here is a simplified version of what I have :

1. The route accesses to differents models. This works fine :

   import Ember from 'ember';
   export default Ember.Route.extend({
   
       model() {
           var store = this.store;
   
           return Ember.RSVP.hash({
               fighters: store.findAll('fighter'),
               duels:store.findAll('duel')
           });
       },
   
       setupController(controller, models) {
   
           var fighters = models.fighters;
           var duels = models.duels;
   
           controller.set('fighters', fighters);
           controller.set('duels', duels);
      }
   });
   
   

2. The Controller should save a new duel using the form's values. Here "formdata" is null when the form is submitted

   import Ember from 'ember';
   export default Ember.Controller.extend({
   
       actions: {
           save(formdata) {
                var newduel = this.store.createRecord('duel', {
                     fighter1:formdata.fighter1,
                     fighter2:formdata.fighter2,
                });             
           }
       }
   });
   
   

3. The template displays droplists OK, but I cannot "connect" to the value in the controller, whatever ##FIGHTERn## I try !

    <form >
   <dl>
       <dt>
           <select value='##FIGHTER1##'>
               
                   <option value=></option> 
               
       </select>            
       </dt>
   
       <dt>
          <select value=##FIGHTER2##>
               
                   <option value=></option> 
               
           </select>  
       </dt>
   </dl>
   <button type="submit">Add</button>