Colonisation of spring wheat spikelets by soil phytopathogens in the Western Siberian forest-steppe

Abstract

The research aimed to assess the influence of varieties and yearly conditions on phytopathogens' colonisation of spring wheat spikes. The study tasks included specifying the mechanisms and timing of colonisation by phytopathogens, determining the taxonomy of microfungi groups and species related to various generative organs, and identifying the impact of varieties and yearly conditions on microfungi colonisation of generative organs. The research was conducted in 2021-2022 in the northern forest steppe of the Ob region on ten spring wheat varieties from various areas of Russia and the world, using standard methodologies. Of the two experimental years, 2021 was relatively humid (GTU August 1.2), while 2022 was dry (GTU August 0.45). In the research years, the mycobiota of generative organs of spring wheat varieties consisted of Bipolaris sorokiniana Sacc. Shoem, fungi of the Fusarium Link genus, and Alternaria Nees. However, the taxon representation significantly differed between years, varieties, and spike organs. The dynamics of colonisation of generative organs of spring wheat varieties by microfungi suggest early infestation of spikelet peduncles by Fusarium fungi (tubular stage) and B. sorokiniana (stem elongation stage). It indicates the ability of these microfungi to infect spikes through vessels and by airborne-droplet transmission. The study of the collection did not reveal varieties resistant to the infestation of generative organs by B. sorokiniana and Fusarium and Alternaria fungi. B. sorokiniana preferred infesting spikelet peduncles over grains and increased spike colonisation in wetter conditions. B. sorokiniana dominated on spike peduncles in both years of the study and on grains in the wetter 2021. Fusarium fungi demonstrated lower colonisation activity of generative organs in dry and wet conditions, with a higher affinity for spikelet peduncles, which was less dependent on the yearly conditions. In contrast, the colonisation of grains depended on yearly conditions and was 1.9 times lower on average across varieties in dry conditions. Alternaria fungi preferred colonising grains over spikelet peduncles in spring wheat varieties. They were more successful in dry conditions, unfavourable for moisture-loving phytopathogens from the Fusarium and B. sorokiniana genera. They dominated on grains of all collection varieties in the dry 2022.