Influence of Agroclimatic Conditions, Life Form and Host Species on the Species Complex of Wheat Septoria Pathogens

Abstract

Currently, septoria is the basis of the pathogenic complex on wheat crops in Russia, occupying the predominant position among harmful fungal diseases. In case of severe wheat damage, the crop loss caused by the fungus Z. tritici, makes up from 10–25 to 40–60%. The crop loss caused by the fungus P. nodorum parasitizing is from 10–20 to 30–50% during the years of epiphytoty. The question of the economic significance of P. avenae has not yet been examined completely. However, depending on the area of wheat cultivation and the year of observation, its part in the septorian population may reach up to 76.9%. It was of interest to study in detail the influence of conditions of the specific year, life form, and species of wheat on the formation of the species composition of Septoria in the pathogenic complex of wheat. Among the complex set of factors included in the concept of the environment, a significant role belongs to its abiotic components, namely, climate and weather, but the variety as an environment-forming factor has a decisive role. Our studies were carried out during 2010–2017. During the research period, the weather conditions varied significantly over the years and were not always favorable for the development of plants and formation of a good wheat crop. During the study, deviations in the amount of precipitations during the vegetation period, and, in general, over the year from the long-term average annual values, were noted. The years of 2012, 2014 and 2015 were characterized by the highest moisture supply during the vegetation season. It has been predicted that cooler days of April and May will promote the better development of P. avenae and P. nodorum. P. nodorum receives its predominant development during the years with wetter weather within the vegetation period of wheat, in contrast to Z. tritici more resistant to low humidity. These data demonstrate adaptation of the pathogen to conditions of an increased temperature regime and reduced rainfall amount.