Diagnostic tools, epidemiology of Alternaria dauci on seed carrots, and control methods

Alternaria dauci is a pathogen that frequently affects carrot seeds, impacting their germination capacity. The research carried out has led to the development of detection tools based on PCR primers targeting the ITS regions, which are almost exclusively specific to the species Alternaria dauci. Intraspecific identification tools based on the IGS regions and microsatellite loci have also been developed, highlighting the high genetic variability of the species A. dauci. From an epidemiological perspective, a key for identifying leaf blight has been established. It has been demonstrated that the plant is susceptible to the pathogen at any stage of its development; however, the climatic conditions conducive to the pathogen’s development could not be clearly established. The study of the efficacy of fungicides identified three effective products (SIGNUM, AMISTAR and, to a lesser extent, TWIST), and demonstrated the existence of strains resistant to iprodione. Finally, the Tomcast model, adapted for Alternaria leaf spot on carrots by the CTIFL, underwent initial field trials on seed-bearing plants during this programme. This model is currently under development.