Series/Report Number: COARC2014

Abstract: Bacterial soft rot can be an important disease of carrots, including carrot stecklings used for hybrid carrot seed production. The objectives of this study were to: 1) identify the causal agent of soft rot in carrot stecklings; and 2) determine the incidence and potential impact of soft rot in two steckling-planted carrot seed fields. Three bacterial isolates obtained from symptomatic carrot stecklings were identified as Pectobacterium carotovorum subsp. carotovorum (syn. Erwinia carotovora) using DNA sequencing. Approximately 16 to 22% of male plants and 12 to 22% of female plants were dead by the time of the first survey in early June, presumably due to soft rot. By early August, between 22 and 43% of female plants exhibited soft rot symptoms in the two fields. Although yields data was not collected, these results suggest that soft rot can have a major impact on field stands, and subsequently yield, in certain steckling-planted carrot lines.