Susceptibility of Cotton Varieties to Verticillium Wilt in Apsheron Conditions

Cotton, is one of the oldest plants belonging to the genus of Gossypium. In this genus 37 species is known, that belong to the family of Malvaceae. In cultivation, there are 5 types of cotton: Mexican - G. hirsutum L., Peru - G. barbadense L., Asian - G. herbaceum L., Indo-Chinese - G. arboreum L. and Vestindiysky - G. tricuspidatum L. They are the source of natural plant fibers that are used to generate a variety of textile fabrics, and many other products. Improving productivity and increasing the total yield of the spinning crops is based on the introduction of new, more productive varieties. But, high and stable yield of cotton faced to a lot of difficulties. One of them is defeat of plant by pests and diseases like root rot, gummosis and wilt. Particularly, the harmful one is wilt that can be caused by two pathogens - Verticillium and Fusarium. Cotton cultivars in the species of G. hirsutum L. mainly affected by Verticillium wilt and species of G. barbadense L. by Fusarium wilt. The pathogens of Verticillium and Fusarium wilt are transmitted from affected residues. These residues are microscopic fungi can remain viable for several years. In the favorable conditions, they germinate and its fungus strands penetrate in the roots of susceptible plants and then spreads on the aerial organs. The most radical way to protect plants against diseases is the creation of new disease-resistant varieties. We conducted phytopathological assessment of cotton varieties resistance to Verticillium wilt on the artificially-infectious background. The pathogen of Verticillium wilt is the fungus Verticillium dahliae Klebahn. This is an organism of soil from the class of imperfect fungi, polyphagous, infects more than 400 species of plants belonging to different families. For the analysis taken 70 cotton varieties purchased from the Institute collection of the G. hirsutum L. Results showed: 4.3% turned out to be immune varieties, 7.1% - as highly resistant, 14.3% - as resistant, 51.4% - as tolerant, and 22.9% - as susceptible. The first symptoms of diseases on plants were observed at the stage of germination in the phase of 1-3 true leaves. These plants were rapidly losing all the leaves and completely dried up at the beginning of the growing season. The number of early diseased plants was not large. With further development of cotton the number of infected plants gradually increased, and on the phase of early flowering, disease became noticeable. The massive display of wilt is occurring during fruiting.