Enhancement of adaptive capacity of sugar beet crops by microbial biopreparations under biotic and abiotic stresses

Diseases caused by pathogenic micromycetes and impact of herbicides lead to lower productivity and quality of sugar beet. Biopreparations based on Bacillus Cohn are promising environmentally friendly agents for plants protection under biotic and abiotic stresses. Meanwhile it is important to search of bioregulators for application on sugar beet and identify the mechanisms of their actions for effective use. This study summarizes the results of analysis of the effect of Bacillus Cohn based biopreparations Fitosporin-M, Albit, Vitaplan on structure of pathogenic mycromicetes complex in sugar beet ( Beta vulgaris L., cv. KVS) rhizosphere, enzymatic activities in soil and leaves, sucrose content in roots and productivity under pathogenic and herbicides pressing. Evaluations were carried out using classical microbiological, physiological and biochemical methods. It was revealed that Fitosporin-M, Albit, Vitaplan decreased the abundance and frequency of rhizosphere pathogenic species and thus lead to activation of useful microflora. Partilularly, a total of 8 pathogenic micromycetes were found in control of which Alternaria tenuis, Aspergillus niger and Penicillium glabrum, the last two being strong toxigenic isolates, were dominant. After a single treatment with Fitosporin-M only Penicillium glabrum was found in the rhizosphere, in case of Albit there was only P. citrinum, and at Vitaplan application Alternaria tenuis, Aspergillus niger, Fusarium oxysporum, F. solani and Penicillium solitum were identified. In plants treated with Fitosporin-M and Albit, no Black Leg pathogens were observed. After doubled treatment the abundance decreased 1.5-3.0-fold, and the frequency decreased 2.0-4.0-fold compared to control. Catalase activity reflecting intensity of soil microbiological processes exceeded control from 1.4 to 3.7 times after the first treatment with Fitosporin-M and Albi, respectively, and from 1.4 to 1.2 times after the second one. The data on increasing oxidoreductases and hydrolases activities in rhizosphere confirm this conclusion. Also, biopreparations decreased activities of hydrolases in leaves and the activity of their inhibitors indicating induction of protective reactions against pathogens. The maximum values were recorded when Fitosporin-M and Albit were used. The protective actions of biopreparations were also indicated by activation of peroxidase in leaves up to 0.175-0.250 OD 490 per 1 g. Furthermore Fitosporin-M supported a relatively high level after reintroduction indicating a prolonged action on the antioxidant system during vegetation. The positive effect of biopreparations under pathogenic and herbicides pressing was reflected in increasing productivity and sucrose content in sugar beet roots, and the maximum effect was achieved after 2-fold treatment of sowings with Fitosporin-M.