First report of Colletotrichum gloeosporioides causing 'twister disease' of onion (Allium cepa) in Georgia.

In the fall of 2007, onion seedlings with twisted and distorted leaves were observed in seedbeds in multiple fields in the Vidalia onion region of Georgia. Tests for viruses and bacteria were negative and chemical injury was deemed improbable because of disease distribution in the fields. Upon further investigation, fungal fruiting bodies were observed on the outside sheath of a few of the seedlings. Symptomatic plants were cut into 1-cm segments and surface sterilized in 70% ethanol for 3 min. After rinsing in sterile water, the segments were placed onto potato dextrose agar amended with tetracycline. The fungus isolated from symptomatic plants fit the description of Colletotrichum gloeosporioides (Penz.) Penz. & Sacc. Conidia were aseptate, cylindrical, and hyaline. Sequencing of the internal transcribed spacer region and a BLAST search in GenBank (99% sequence similarity to C. gloeosporioides accessions) confirmed the identification. Ten onion seedlings were spray inoculated with a suspension of 1 × 10...