Mycelial compatibility of Phomopsis helianthi (Munt.-Cvet. еt al.) isolates

In the present study, the genetic diversity of 30 isolates of the pathogen Phomopsis helianthi was studied using the mycelial compatibility groups (MCGs) method. Mycelial compatibility tests were carried out on two media - PDA + 80 µl/L and PSA +80 µl/L, with added colorant (Christmas red - Sly Commerce OOD) and without added colorant. The use of PDA medium was found to be inadvisable due to the indistinct dividing line (groove) in isolates having an incompatible phenotypic response. Based on the tests done, 416 combinations were carried out and the four types of reaction were observed- NC-N – incompatible with necrosis, NC-Gincompatible, mycelium do not approach with a pronounced distance between them, NC-DL- both lines (black) are spaced, C-compatible. Their percentage ratio is presented. Isolates are grouped into 20 MCGs, with two of the groups containing only one isolate due to their incompatibility. The remaining isolates were found to occur in more than one MCG. The isolates originating from the region of Ruse were marked with the greatest genetic diversity, and the isolates from the area of Karnobat with the least.