Transcription factor that regulates the expression of the gene clusters that mediate the biosynthesis of the host-selective toxins (HSTs) AF-toxins responsible for Alternaria black spot of strawberry disease by the strawberry pathotype (Probable). On cellular level, AF-toxins affect plasma membrane of susceptible cells and cause a sudden increase in loss of K(+) after a few minutes of toxin treatment (PubMed:22846083). Gene clusters encoding host-selective toxins (HSTs) are localized on conditionally dispensable chromosomes (CDCs), also called supernumerary chromosomes, where they are present in multiple copies (Probable). The CDCs are not essential for saprophytic growth but controls host-selective pathogenicity (Probable).