Submitted to: Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/28/2004
Publication Date: 10/1/2004
Citation: Babadoost, M., Chen, W., Bratsch, T., Eastman, C.E. 2004. Verticillium longisporum and fusarium solani: two new species in the complex of internal discoloration of horseradish root. Plant Pathology. 53:669-676. Interpretive Summary: Internal discolopration of horseradish causes significant economical losses to horseradish growers. Experiments were conducted to determine the cause agents of this disease of horseradish. A number of microorganisms were isolated from horseradish roots showing internal discoloration. Two new pathogens were identified from horseradish. They are Verticillium longiporum and Fusarium solani. Laboratory and greehouse experiments showed that these two pathogens cause symptoms on horseradish similar to those observed in commercial fields. Results from this study and previous studiey show that internal discoloration of horseradish is a disease complex caused by several pathogens.
Technical Abstract: This study was conducted to determine the causal agent(s) of internal discoloration of horseradish roots. In 1999, 133 roots from 31 fields, and in 2000, 108 roots from nine fields, were assayed to determine severity of internal discoloration of horseradish roots and pathogen(s) associated with discolored tissue. Verticillium dahliae, V. longisporum, and Fusarium solani were isolated from 14, 16, and 23% of roots in 1999; and 24, 20 19% of roots in 2000, respectively. V. longisporum was identified for first time on horseradish. Pathogenicity tests of isolated microorganisms were conducted on horseradish in the greenhouse. In one experiment on horseradish cultivar 1573, horseradish roots (sets) were inoculated by dipping the sets in suspension of V. dahliae and V. longisporum microsclerotia and F. solani conidia and grown in a soil mix over five months. In another experiment on horseradish cultivar 1590, horseradish sets were planted in an infested soil mix with V. dahliae or V. longisporum and grown in the greenhouse. Inoculated plants with all three pathogens in both experiments developed root discoloration similar to those observed in the commercial fields and the pathogens were reisolated from inoculated roots. The results of this study showed that internal discoloration of horseradish root is a disease complex caused by several pathogens