Genetic analysis of barrage line formation during mycelial incompatibility in Rosellinia necatrix

When mycelia of Rosellinia necatrix encounter mycelia of a different genetic strain, distinct barrage lines are formed between the two. These barrages have variable features such as pigmented pseudosclerotia structures, a clear zone, fuzzy hair-like mycelia, or tuft-like mycelia, suggesting that mycelial incompatibility triggers a number of cellular reactions. In this study, to evaluate cellular reactions we performed genetic analysis of mycelial incompatibility of R. nectarix, using 20 single ascospore isolates from single perithecia. Mycelial interaction zones were removed by spatula and cellular reactions studied on oatmeal agar media. The interaction zones were categorized into types such as sharp or wide lines, with or without melanin, and combinations of these. Although various reaction types were observed, we were able to identify a single genetic factor that appears to be responsible for the barrage line formation within oatmeal agar medium. DNA polymorphism analysis identified parental isolates and revealed that R. necatrix has a heterothallic life cycle.