Field evaluation of mutant and hybrid lines of mint for resistance to Verticillium wilt and yield

Abstract

Mint lines that were previously identified with low wilt-severity values in the greenhouse were evaluated for resistance to Verticillium wilt and yield in the field in the presence of naturally occurring inoculum and in plots artificially infested with the soilborne fungus. Severity of Verticillium wilt varied significantly among mint lines and cultivars in the inoculated and non-inoculated sub-plots in two field trials. Verticillium wilt was significantly less severe for mutant lines 87M0109-1, 84M0107-7, and M90-11 than for Black Mitcham in 2002 and 2003. Verticillium wilt was significantly less severe for mutant line M83-14 and for Murray Mitcham than for Black Mitcham in 2003 and 2004. At the completion of the first trial, fresh hay yields of both peppermint hybrids 87M0109-1 and 84M0107-7 and peppermint mutant M90-11 were significantly higher than the standards Black Mitcham and Redefined Murray Mitcham. Oil yield in the first trial of standard Black Mitcham declined in years 3 and 4, while the decline in oil yield was less dramatic with the other four peppermint lines. In the second trial, hay yields of both B90-9 and M83-14 were comparable to, but not significantly different from Black Mitcham and Redefined Murray Mitcham. Line 92(B-37 × M0110)-1 yielded significantly less oil than all peppermint lines including both standards Black Mitcham and Redefined Murray Mitcham in six of the seven cuttings in the second trial. Verticillium rating of the lines and cultivars inoculated in trials from a previous greenhouse study were highly correlated with the Verticillium wilt rating of the lines and cultivars the second and third years when inoculated in both field nurseries in this study. Verticillium wilt resistance and yield can be improved in commercial mint cultivars and form a basis for managing the disease.