A Destructive Leaf Spot and Blight Caused by Alternaria kareliniae sp. nov. on a Sand-Stabilizing Plant, Caspian Sea Karelinia.

Leaf spots and stem lesions causing widespread mortality of Caspian Sea karelinia (Karelinia caspia) were observed in desert regions of Xinjiang Uyghur Autonomous Region, China. Fifteen samples were collected from five widely distributed counties of Tarim and Junggar Basins in 2016. The pathogen was identified using morphological observations and phylogenetic analyses based on combined partial sequences from seven genes (Alt a 1, ATPase, calmodulin, glyceraldehyde 3-phosphate dehydrogenase, internal transcribed spacer, RNA polymerase II, and translation elongation factor 1), and placed as a new species: Alternaria kareliniae sp. nov. in section Dianthicola. The fungus has a small conidium (24.3 to) 29.1 to 64.8 (to 75.8) by (9.3 to) 12.4 to 16.5 (to 21.7) μm with a long beak (130 to) 183.9 to 350.4 (to 378.2) μm, as well as four to eight transverse septa, which differs significantly from other species of Alternaria section Dianthicola. On potato carrot agar, it grew significantly more slowly than others of this section. Pathogenicity tests showed that the fungus could infect leaves and stems of K. caspia and cause the same symptoms as those observed in the field. The fungus was reisolated from inoculated leaves and stems of the host. The disease in desert regions appears to be increasing, and it may have future negative implications for desert ecology in these areas. Future research should concentrate on elucidating the disease cycle and disease management alternatives.