Races of mint rust (Puccinia menthae Pers.) on cultivated peppermint and other hosts in New Zealand

Abstract

Twelve isolates of Puccinia menthae collected from Mentha × cordifolia (winter mint), M. × piperita (peppermint), M. × piperita var. citrata (lemon mint), and M. spicata (spearmint) were testéd for differences in pathogenicity on 26 clones from 6 species in Mentha and 5 species in related genera. Three races were identified from the differential host reactions: Race 1 was isolated from M. × piperita and M. × piperita var. citrata; Race 2 from M. x cordifolia and M. spicata; Race 3 from M. spicata. Although M. × piperita has been naturalised in New Zealand for many years, and commercially grown since 1970, the first record of rust on this species was on cultivated plants in December 1978. Observations of wild mint clones along river banks in the peppermint growing area of Canterbury during 1979 and 1980 suggest that rust spread from infected peppermint crops to wild M. × piperita var. citrata and M. × piperita. Race 1 thus appears to be a recent arrival in New Zealand. The earlier New Zealand records on the introduced mint species M. × cordifolia and M. spicata are probably attributable to Races 2 and possibly 3, neither of which attack peppermint.

Keywords:

• Mint rust
• Mentha
• Puccinia menthae
• pathogen
• plant pathology
• plant diseases
• rusts
• Uredinales
• Basidiomycetes
• fungi