Macrophomina phaseolina (Tassi) Goid. is found on all five crop-growing continents. In hot and dry seasons, this fungus is capable of causing considerable damage. In this study, mycelial compatibility of M. phaseolina isolates was investigated. In total the 30 samples collected were tested to examine their compatibility. The sunflower samples examined were collected in 2019 and 2020 in different regions of Hungary (29 isolates) and Slovakia (1 isolate). A total of 465 pairing tests were made with 30 isolates. The results of our examination showed incompatibility in 12 pairings. In our studies, we also measured the size of the microsclerotia of the isolates in order to determine which group they belong to. The diameter of the microsclerotia ranged from 74 to 182 μm. Based on this, microsclerotia belong to group ‘C’, as well as the data of previous studies in Hungary.
