Investigation of species composition of the fungi of the Fusarium genus and the resistance of the Chornobyl radio-mutants to fusarium head blight for the purposes of winter wheat

Aim. To investigate the field resistance of collection spelt-like samples of the Chornobyl radio-mutants (RM) of winter wheat to Fusarium head blight and to determine the species composition of the fungi of the Fusarium genus in the Forest-Steppe of Ukraine. Methods. The resistance (in scores) of ten RM-samples of winter wheat to Fusar- ium head blight was determined in field conditions by visual inspection of plants using standard methods (Trybel et al, 2010). To determine the infection rate of the seeds, the biological method of seed germination in the rolls of filtration paper was used. DNA was extracted using the reaction kit AGROSORB NK (Agrogen Novo, Ukraine), according to the manufacturer’s instructions. The molecular identification of the species composition of the fungi of the Fusarium genus was conducted with the commercial test systems “Fuzarioz zlakiv” (AgroDiagnostica, RU) according to the manufacturer’s instructions, using the real-time PCR. Results. The results of evaluating the field resistance of ten spelt-like RM-samples of winter wheat to Fusarium head blight are presented. The species composition of the Fusarium fungi as of 2016–2018 in the Forest-Steppe of Ukraine, namely in Kyiv, Cherkasy, Sumy, Vinnytsia, Chernivtsi, Poltava, Kharkiv, Ternopil, and Khmelnytsky regions is presented. To study the spe- cies composition of the Fusarium fungi, 639 seed samples of winter wheat were taken from the farms located in the territory of nine regions in the Forest-Steppe zone. The results of molecular identification of the infection rate in the seed material demonstrate the presence of seven out of eight fungi species under investigation: F. avena- ceum, F. culmorum, F. graminearum, F. langsethiae, F. poae, F. sporotrichioides, F. tricinctum during the years of studies. Yet, F. culmorum, F. langsethiae were not identified in 2017, and F. cerealis was not found during the study years, in 2016–2018. It should be noted that the most frequent incidence was found for F. graminearum, F. avenaceum and F. tricinctum, which was within the range of 25.8–44.0 %, and according to (Zhdanova, 2002) it refers to the group of frequently dispersed species. The results of the PCR diagnostics of the species composition of Fusarium fungi in Kyiv region, where field studies were conducted to evaluate the resistance of collection spelt- like Chornobyl radio-mutants in 2016–2018 (Bila Tserkva Breeding Research Station (BTBRS) of the Institute of Bioenergy Crops and Sugar Beet of the NAAS (Mala Vilshanka village, Bila Tserkva district, Kyiv region) demonstrated the spreading of six species of Fusarium fungi: F. graminearum, F. avenaceum, F. sporotrichioides, F. poae, F. tricinctum, F. culmorum, among which high aggressiveness to the wheat spikelets was observed in F. avenaceum, F. culmorum, F. graminearum; medium aggressiveness – in F. poae, and low aggressiveness – in F. sporotrichioides, F. tricinctum. On the background of the obtained species diversity of the disease agent, we evaluated the field resistance in ten spelt-like RM-samples of winter wheat to Fusarium head blight, whose resistance fluctuated within 7.4–8.4 scores in the study years. Under the climatic conditions most favorable for the disease development, in 2016 (from the time of spring vegetation restoration on March 01, to full ripeness of grain on July 09, there was 404.2 mm of precipitation which exceeded the perennial indices by 175 %) the samples under investigation: RM-1, RM-3, RM-4, RM-5, RM-6, RM-9, RM-10 exceeded the resistance of the standard variety, Lisova Pisnia, – 7.0 scores. Conclusions. The field and laboratory studies related to the species composition and geographic distribution of the Fusarium fungi give grounds for the assumption of the presence of an expansive species complex of Fusarium fungi in the territory of nine regions in the Forest- Steppe of Ukraine: F. avenaceum, F. culmorum, F. graminearum, F. langsethiae, F. poae, F. sporotrichioides, F. tricinctum. A close association between the biology of the group of Fusarium fungi and weather conditions of their environment was used by us to investigate the resistance of ten collection spelt-like samples of the Chornobyl radio-mutants in 2016–2018 and to isolate five RM-samples of winter wheat (RM-9, RM-5, RM-6, RM-10, RM-4), which had higher resistance to Fusarium head blight than the standard variety, Lisova Pisnia, on average for three years of studies. It should be noted that in 2016, under weather conditions favorable for pathogen development, RM-3 and RM-4 were found to be reliably more resistant compared to the standard. The five spelt-like RM-samples of winter wheat (RM-9, RM-5, RM-6, RM-10, RM-4) with high resistance indices on average for the years of studies (2016–2018) are introduced by us to the breeding programs as the initial material to obtain varieties, resistant to Fusarium head blight.