Nova Biotechnol Chim (202x) 22(x): e1387 DOI: 10.36547/nbc.1387 1 Nova Biotechnologica et Chimica The influence of inoculation and drought on the diversity of fungal communities in the roots of tomato plants Katarína Ondreičková 1,  , Marcela Gubišová 1 , Katarína Hrčková 1 , Martina Hudcovicová 1 , Jozef Gubiš 1 , Miroslav Horník 2 , Silvia Dulanská 3,4 1 National Agricultural and Food Centre – Research Institute of Plant Production, Bratislavská cesta 122, Piešťany 92168, Slovak Republic 2 Department of Ecochemistry and Radioecology, Faculty of Natural Sciences, University of SS. Cyril and Methodius in Trnava, Nám. J. Herdu 2, Trnava 91701, Slovak Republic 3 Institute of Medical Physics, Biophysics, Informatics and Telemedicine, Faculty of Medicine, Comenius University, Sasinkova 2, Bratislava 81372, Slovak Republic 4 Faculty of Public Health, Slovak Medical University, Limbová 12, Bratislava 83303, Slovak Republic  Corresponding author: katarina.ondreickova@nppc.sk Article info Article history: Received: 25 th January 2022 Accepted: 1 st February 2022 Keywords: Alpha diversity Arbuscular mycorrhiza Fungal diversity Plant stress Pot experiment Abstract Arbuscular mycorrhizal fungi (AMF) are microorganisms with very important functions in agricultural systems. Since arbuscular mycorrhiza is one of the most common types of mycorrhizae, the diversity of AMF is very varied. Their diversity can be influenced by various biotic and abiotic factors. Of these, drought is one of the most common abiotic stresses in agriculture. In this study, we evaluated the influence of drought and inoculation with three species of AMF ( Rhizoglomus irregulare, Funneliformis mosseae and F. caledonium) on the fungal genetic diversity in the roots of tomato plants (Solanum lycopersicum L.) using partial 18S rRNA gene in molecular fingerprinting method. Two conserved primer pairs NS1– NS4 and NS31–AM1 in Nested PCR were used. The second primer pair is specific for AM fungi from Glomeromycota, but also amplifies DNA from Ascomycota and Basidiomycota to a very small extent. Drought caused a decrease in fungal alpha diversity in tomato roots of non-inoculated plants. On the other hand, an increase of this diversity due to drought in inoculated plants was observed. Based on principal component analysis, a statistically significant shift in the composition of fungal communities in non-inoculated and inoculated plants due to drought was not detected. At the same time, the most variable fungal communities were in control well-watered and non-inoculated plants, but this variation was not significant.  University of SS. Cyril and Methodius in Trnava Introduction Arbuscular mycorrhizal fungi (AMF) which form a symbiosis with approximately 80 % of terrestrial plant species have an important role in processes such as increasing mobilization and nutrient transfer, plant tolerance to root pathogens, production of plant growth hormones, plant biodiversity, adaptation of the plant to adverse environmental conditions, the absorption capacity of plant roots, and many others (Garg and Chandel 2010). Adverse external conditions for plants whose effect AMF can decrease are drought, salinity, heavy metal toxicity, soil acidification, or heat (Finlay 2008). Of these, drought is one of the world's most abundant abiotic stress (Zhang et al.