Variability of cotton (Gossypium hirsutum L.) with regard to earliness

Eighty cotton varieties (Gossypium hirsutum L.) from the collection of VIR (N.I. Vavilov Research Institute of Plant Industry, St. Peterburg, Russia) collection were studied for variability with regard to the duration of their vegetation period. The experiments were carried out in the conditions of the marginal zone of the cotton growing area, that is the city of Krasnodar in the Russian Federation. Thirty-four varieties were studied in 1996–1998, forty-six varieties in 1997–1998. The purpose of this research was to determine the threshold of sensitivity in the varieties of the duration of the period of vegetative growth, which depends upon weather conditions, and to record variations in morphological characters associated with earliness. The data obtained were processed by the method of statusmetry. The mathematical models which were constructed showed the relationship between the criteria for earliness and other morphological and agronomic characters of the plants.