Nested model form problem, not saving, any help?

I have two models, Curso and Ementa

class Curso < ActiveRecord::Base
attr_accessible :nome, :descricao, :periodo_inscricao_inicio, :periodo_inscricao_fim

has_one :ementa, :dependent => :destroy
has_many :turmas
has_many :publico_alvos

accepts_nested_attributes_for :ementa

end

class Ementa < ActiveRecord::Base
belongs_to :curso
end

One form for hadle both models

<% form_for @curso do |f| %>
<%= f.error_messages %>

<%= f.label :nome %>
<%= f.text_field :nome %>

<%= f.label :descricao %>
<%= f.text_area :descricao %>

<%= f.label :periodo_inscricao_inicio %>
<%= f.date_select :periodo_inscricao_inicio %>

<% fields_for :ementa do |ementa_form| %> <%= ementa_form.label :descricao, "Ementa" %> <%= ementa_form.text_field :descricao %> <% end %>

<%= f.label :periodo_inscricao_fim %>
<%= f.date_select :periodo_inscricao_fim %>

<%= f.submit "Submit" %>

<% end %>

the controller

class CursosController < ApplicationController
def index
@cursos = Curso.all
end

def show
@curso = Curso.find(params[:id])

respond_to do |format|
  format.html {render :layout=>false}
end

end

def new
@curso = Curso.new
@curso.build_ementa

respond_to do |format|
  format.html {render :layout=>false}
end

end

def create
@curso = Curso.new(params[:curso])
if @curso.save
flash[:notice] = “Successfully created curso.”
redirect_to @curso
else
render :action => ‘new’
end
end

def edit
@curso = Curso.find(params[:id])

respond_to do |format|
  format.html {render :layout=>false}
end

end

def update
@curso = Curso.find(params[:id])
if @curso.update_attributes(params[:curso])
flash[:notice] = “Successfully updated curso.”
redirect_to @curso
else
render :action => ‘edit’
end
end

def destroy
@curso = Curso.find(params[:id])
@curso.destroy
flash[:notice] = “Successfully destroyed curso.”
redirect_to cursos_url
end
end

The result is just one insert on curso table, why it is not inserting on ementa table to the “descricao” field?

Console result: