Accumulation of rishitin in susceptible and resistant tomato plants after inoculation with Verticillium albo-atrum

Abstract

Six-week-old tomato plants of the susceptible cultivar ‘Maascross’ and the resistant cultivar ‘Multicross’ were stem-inoculated with a conidial suspension of 10 7 conidia per ml of Verticillium albo-atrum. Two, 3, 4, 7 and 11 days after inoculation stem pieces cut at 0·5 to 5·5 cm and at 5·5 to 10·5 cm above the site of inoculation were extracted and the concentration of rishitin determined. Rishitin accumulation during the entire incubation period appeared not to be greater in resistant plants than in susceptible ones. The number of propagules isolated from comparable stem pieces of resistant and susceptible plants during the first 4 days after inoculation showed no differences. At 7 and 11 days after inoculation, however, the number of propagules appeared to be significantly lower in resistant plants than in susceptible ones. It is concluded that rishitin accumulation is not a primary factor in resistance.