Development of Wilt in Mint in Response to Infection by Two Pathotypes of Verticillium dahliae and Co-infection by Pratylenchus penetrans.

Abstract

Two isolates of Verticillium dahliae in vegetative compatibility group (VCG) 2B and one isolate in VCG 4A were tested for aggressiveness on peppermint, Scotch spearmint, and native spearmint alone and in combination with the lesion nematode Pratylenchus penetrans. The VCG 2B isolates were more aggressive than the VCG 4A isolate on all three mint species. Severity of wilt was greatest on peppermint and scotch spearmint with the VCG 2B isolates, and CFU of V. dahliae recovered from infected stems were greater in Scotch spearmint when inoculated with V. dahliae and P. penetrans than when inoculated with VCG 2B alone. Wilt severities and CFU in peppermint and Scotch spearmint were not increased when inoculated with VCG 4A and P. penetrans compared with VCG 4A alone. These data indicate that V. dahliae isolates from VCG 2B but not VCG 4A interact synergistically with P. penetrans on Verticillium isolate-susceptible mints. The resistance to Verticillium isolates in native spearmint was not affected by the presence of lesion nematodes.