THE INFLUENCE OF THE PREDECESSOR AND SOWING DATES ON THE DEVELOPMENT OF SEED INFECTION OF WINTER WHEAT VARIETIES IN THE CONDITIONS OF THE FOREST-STEPPE OF UKRAINE

Abstract

Diseases of winter wheat in agrocenoses can be caused by various factors, but one of the key factors is the accumulation of phytopathogenic microbiota in soil, seeds, and plant residues. The leading role in the pathogenesis is played by representatives of the genus Fusarium Link and Alternaria Nees, which lead to a decrease in grain yield and its quality indicators. In addition, a specific of Fusarium fungi is their ability to produce mycotoxins as secondary metabolites of microscopic fungi that contaminate food and feed and are very dangerous and toxic to humans and animals. Eating foods contaminated with mycotoxins has a devastating effect on cells, tissues, and organs. Recently, due to crop rotation disruptions and oversaturation with cereal crops, the introduction of various minimum tillage technologies and changes in agroclimatic conditions, there have been significant changes in the development, spread and harmfulness of pathogens in Ukrainian agrocenoses. An important role in the level of seed infection is played by sowing dates and the crop that was grown on the field before the wheat. Therefore, as a preventive measure, it is necessary to adhere to the optimal sowing dates and preceding crops, due to which the plants will be able to avoid the dangerous moment, as the infection will not have time to spread on the crops during the flowering phase. The purpose of the research was to determine the effect of winter wheat sowing dates and preceding crops on the level of grain infection with Fusarium and Alternaria pathogens. The research was carried out on winter wheat varieties bred at the V.M. Remeslo Myronivka Institute of Wheat of the National Academy of Agrarian Sciences of Ukraine Podolianka, MIP Lakomka, Avrora Myronivska, MIP Fortuna, MIP Lada, and MIP Yuvileina sown in two terms (I – September 25, II – October 5) after soybean and sunflower in the conditions of the Central and North-Eastern Forest-Steppe of Ukraine. In laboratory conditions, the number of grains with Fusarium and Alternaria infection was determined in grain samples of each the variety. For this purpose, an average sample was taken, rinsed with running water, surface disinfected in Domestos solution (1 : 20) (we substituted 0.5% KMnO4 solution, which is our measure for one of the types of disinfection), followed by rinsing with sterile distilled water, flamed in an ethanol lamp flame and streaked of 10 pcs in 10 replicates on sterile nutrient medium (potato glucose agar (PGA) with the addition of an antibacterial antibiotic, streptomycin sulfate) poured into Petri dishes. The Petri dishes with seeds were incubated in a thermostat at 25°C for five days. After five days, each micromycete released from the seed to the surface of the nutrient medium was sown into a separate tube with РGA for further identification of the pathogen species using a microscope according to special methods. The degree of the disease progress depends on the variety and agricultural practices by 70% and on weather conditions by 30%. In modern intensive grain growing technologies, one of the unresolved problems in winter wheat plant protection is insufficient control of seed infection, which causes a number of diseases, including Fusarium head blight and black head blight. During the years of the research, winter wheat grain was contaminated with Fusarium Link and Alternaria Nees. The level of seed infection of winter wheat sown after the soybean as preceding crop was lower compared to the sunflower. In the conditions of the central Forest-Steppe of Ukraine, the grain of the studied winter wheat varieties of the first sowing date was less affected by the pathogen Fusarium, but more by the pathogen Alternaria compared to the second date, regardless of the preceding crop. Thus, on average, over the years of the research, the proportion of grains with internal infection of fungi of the genus Fusarium Link was observed in the range of 0.5–14.0% at the first sowing date and 0.7–17.3% at the second sowing date. The level of grain infection with Alternaria Nees varied from 39.8% to 59.0% at the first sowing date and from 31.2% to 57.1% at the second sowing date. It must be noted that the grain of the MIP Yuvileina variety sown after the sunflower as preceding crop was affected by Fusarium pathogen less than the average value for the experiment for both sowing dates in all years of the research. And in 2019 and 2020, the variety MIP Lakomka was distinguished with the number of grains with the pathogen Alternaria less than the average value for the experiment at both sowing dates. A greater accumulation of seed infection was found in the grain of varieties grown in the North-Eastern Forest-Steppe of Ukraine. However, under such conditions, the seeds of the studied varieties of the second sowing date were less affected by Fusarium pathogen regardless of the preceding crop and by Alternaria in the first sowing date with soybean the preceding crop, unlike the grain grown in the Central Forest-Steppe of Ukraine. On average, over the years of the research, the level of grain infection with Fusarium Link varied from 0.8% to 23.5% on the first sowing date and from 0.6% to 27.3% on the second sowing date. The proportion of grains with internal infection with fungi of the genus Alternaria Nees was within 35.1–65.0% at the first sowing date and 39.3–71.6% at the second sowing date. During the years of the research, grain of MIP Fortuna variety, both at both sowing dates and with both preceding crops, was affected by seed infection pathogens less than the average value for the experiment. The choice of optimal sowing dates and preceding crops is essential part of winter wheat cropping practices and, at the same time, the basis of modern plant protection systems against a range of pests, which allows us to unlock the genetic yield potential of each variety.