I am trying to classify cotton (G.hirsutum) according to earliness. I want to use this model to limitation early, medium and long period varieties using with growing day degrees (GDDs). I read many papers but I couldn't find any border about GDDs. I want to use 3 main stages:
1-First squares stages
2-First flower stages
3-Boll opening time
Do anyone offer me the limit number for earliest variety, medium and long period variety for gossypium hirsutum?