MONITORING OF BLACK ROOT ROT OF COTTON PLANT CAUSED BY THIELAVIOPSIS BASICOLA (BERK. & BROOME) FERRARIS AND ASSOCIATED MICROFUNGI OF ROOT ROT PATHOCOMPLEX IN SPRING AND AUTUMN IN CERTAIN AREAS OF SURKHANDARYA REGION IN UZBEKISTAN

In the south of Uzbekistan an urgent issue is cotton plant seeding affected by black root rot (BRR). In years favourable for pathogene development significant yield losses are observed up to replanting needed. In the modern literary sources there is no data on the area of spread of the disease, its appearance indicators at different stages of plant development, injuriousness in Uzbekistan. At the same time, significant sums of money are spent on the fight against T.basicola by means of seed treatment, which reduces profitability of cotton growing. The study aim is monitoring of BRR of cotton plant in spring and autumn in Surkhandarya region of Uzbekistan. As a result of phytopathological studies of Sultan cotton plant seeding in 2015 spring and autumn it was determined that field areas with cotton plants, affected mostly by BRR were the following: 10-15 % in Jarkurgan, 20-30 % in Denov, 15-20 % in Termez. 17 samples of affected plants (10-15 plants in each) were collected, including 8 samples in spring, 9 – in autumn and 3 samples of soil. After spring-sample evaluation, the index of plant root disease was 4-5 according to scale of Rothrock, Colyer et al. [22] and with 4-5 leaves. Manifestations of disease were studied in spring and autumn. For development and recovery of T.basicola fungus from plants and soil, the methods of carrot biological attractants and selective medium were used. Morphological features of pathogene were studied. Pure cultures of the main pathocomplex of sprout diseases are allocated in many cotton-breeding world regions: T.basicola; Rhizoctonia solani ; species р. Fusarium Link. : F. oxysporum , F. solani, F. gibbosum, F. verticillioides, F. equiseti, Fusarium sp. Nowadays there are no species resistant to BRR, cultures allocated can be used for creation of high-resistant hybrid combinations and the new cotton plant species.