Mating types and physiological races of Verticillium dahliae in Solanaceae crops in Brazil

Verticillium dahliae is a soil-borne fungal pathogen responsible for vascular wilt diseases in more than 300 dicotyledonous species, including solanaceous vegetable crops. In this study, a collection of 89 Brazilian V. dahliae isolates was characterized by combing molecular information for mating type and physiological race determination, as well as via virulence bioassays employing a set of differentials. Based on the virulence assays, three isolates were classified as race 1, 76 were classified as race 2, whereas ten isolates did not cause any symptom on the tested cultivars.” In race-specific detection, a total of six isolates were identified as race 1, 70 as race 2, and 13 isolates displayed no amplicon with any primer set employed. Therefore, V. dahliae race 2 isolates are currently ubiquitous across major Solanaceae-producing areas in Brazil. Both MAT idiomorphs were detected, but a larger number of the V. dahliae isolates displayed the MAT1–1 (82%) pattern in our molecular analyses. The simultaneous presence of both MAT idiomorphs opens the possibility of sporadic events of sexual reproduction among V. dahliae populations from Brazil, enabling the potential emergence of either new recombinant isolates with broader host ranges or novel physiological races. Our results clearly indicated the need to intensify the search for effective sources of resistance to V. dahliae race 2 in tomato breeding programs under Brazilian conditions.