Not getting custom category field value

On my App I have created two models Tutorial and Tutorial category and for tutorial i have created a string field for category ( in migration ) 'tutorialcategory'.

On tutorial add page I have added a selectbox field to select category and it is saving properly ( I hope ) as I can see the value after saving the tutorial in show page. but when I see full list using json render i can not see the value there.

Note : both models are separate and none of these contains reference field in migration

model code as follows

class Tutorialcategory < ActiveRecord::Base
    attr_accessible :title

    def to_param
        "#{id}-#{title}"
    end
end



class Tutorial < ActiveRecord::Base
  attr_accessible :body, :projectcategory, :rating, :title, :tutorialcategory, :videoid
end