The aim of the research was to study the effect of resource-saving technologies in the cultivation of spring wheat and barley in several regions of Western Siberia on the distribution and taxonomic composition of root rot pathogens, as well as the evaluation of protective measures efficiency. In the context of the resource-saving technologies of crop cultivation in Western Siberia, root rot became of particular relevance; the development of root rot exceeds the thresholds by up to 5-7 times, especially in the first half of the growing season. We identified substantial changes in the taxonomic composition of the pathogen complex of root rot towards expansion of the plant pathogens range by fungi of the Pythium genus and strengthening of the Fusarium genus fungi domination. There is a tendency of the ecological niches of plant pathogens spreading in organs of plants: B.sorokiniana better adapted to topsoil organs and the Fusarium genus fungi-to the underground ones. We identified environmental factors with the greatest impact on strengthening and spreading of the root rot pathogenesis: high number of intra-stem pests, which exceeds the threshold by 2-3 times, contamination of crops with cereal weeds-reserves of root rot pathogens, as well as low microbiological activity and soil suppressive qualities caused by a short growing season and lack of plant residues. We studied the efficiency of improvement methods for the phytosanitary condition of soil and underground plant organs of spring wheat and barley through the introduction of phytosanitary crop rotation and preceding crops, seed treatment and technologies to improve plant resistance in the initial phases of development.
The purpose of the research was to determine the factors of soil phytopathogens parasitic activity at the underground organs of spring wheat varieties, to clarify the etiology of root rot during the growing season. The studies were carried out in 2020-2021 in the northern forest-steppe of the Ob region (West Siberia) using generally accepted methods. A high parasitic activity of soil phytopathogens was established during the entire growing season of spring wheat: the zonal threshold of harmfulness was exceeded at seedlings up to 2.8 times, at bloom stage to 5 times, and at ripeness stage up to 4 times. The host plants susceptibility to infection with phytopathogens increased during the growing season due to abiotic (drought) and biotic (cereal flies) stresses, which neutralized varietal differences. The main phytopathogens at the underground organs of 20 spring wheat varieties were Bipolaris sorokiniana Sacc. Shom. and Fusarium Link. fungi, the occurrence of which at all underground plant organs (primary roots, secondary roots, stem bases) during the growing season was 100%. The dominance of Fusarium fungi increased during the growing season of plants. The biological diversity of Fusarium fungi was maximal in the bloom phase (up to 7 species on secondary roots of one variety). The species composition of Fusarium fungi was represented by permanent species-F. poae (Peck.) Wollenw. and F. oxysporum Schltdl., additional species-F. sambucinum Fuck., F. graminearum Schwabe and F. equiseti (Corda) Sacc., rare-F. solani Koord., F. sporotrichioides Sherb., F. culmorum Sacc., F. heterosporum Nees., F. acuminatum Ellis & Verh. The succession of Fusarium fungi in the system of plant organs and in the phases of vegetation was revealed, and the parameters of realized ecological niches overlap of Fusarium fungi species were determined.
Relevance и methods. In the field experiment in the conditions of sod-podzolic sandy loam soil of the Central region of the Non-Chernozem zone, the influence of four sowing periods (30.04; 05.05; 10.05; 15.05) on the formation of the yield of early-maturing soybean seeds of the variety Svetlayawas studied.Results. When sowing at a later date, the emergence of seedlings was accelerated and a faster development of plants was observed during the growing season. Thus, when sowing on May 15, the duration of the sowing — germination period was reduced by 6 days compared to sowing on April 30, and the duration of the growing season from germination to maturation was reduced by 4 days. When sown on April 30, soybeans reached harvest ripeness steadily in the third decade of August, when sown on May 15, the ripening of soybeans goes to September, which can lead to unstable ripening of seeds, since the temperature regime in September does not meet the requirements of soybeans. The conducted studies have shown that high yields of soybean seeds at the level of 2.73 t/ha can be obtained on the sod-podzolic sandy loam soil of the Central region of the Non-Chernozem zone in favorable weather conditions. The most favorable conditions for the formation of a seed harvest in this region are created when sowing on May 5. When sowing on April 30, decreasesuch indicators as field germination — by 12.7%, plant survival — by 2.2%, the height of the first inflorescence — by 2.6 cm and the biological yield of seeds — by 20.1% . At later sowing dates, there is also a decrease in seed yield by 19.5–40.8% due to a decrease in field germination (by 2.9–4.9%) and the weight of seeds from the plant (by 21.6–32.4%).
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