Characterization of Phoma adonidicola causing a spot blight on Adonis palaestina

Adonis palaestina Boiss. is one of the top three natural sources of red pigment astaxanthin, which has been used as a valuable antioxidant nutraceutical and a feed additive for salmonid fish raising. Since 2004, a blight disease causing significant damage to plants of A. palaestina in Inner Mongolia, China has occurred. The disease caused small, brown lesions on petioles and stems of the host plants. The disease initially appeared in the field as a brown necrosis on lower parts of the plant, and eventually expanded to the whole plant resulting in complete defoliation. The fungus consistently isolated from symptomatic tissues was identified as Phoma adonidicola based on morphological characteristics. Phylogenetic analysis based on LSU (Large Subunit - 28S), ITS (ITS1-5.8S-ITS2 region), and TUB (beta-tubulin) showed that the P. adonidicola isolates fall in the same well-supported clade, which is closely related to Stagonosporopsis ajacis. All isolates of P. adonidicola also caused typical spots on inoculated plants, and were successfully reisolated from the symptomatic tissues. The disease of A. palaestina was proposed as spot blight.