The effect of varietal resistance on the epidemiology of Pachymetra root rot

Croft (1989) developed a glasshouse technique for screening varieties for resistance to Pachymetra chaunorhiza. Resistance ratings were based on the number of rotted primary shoot roots as a percentage of total root number. Croft found that varieties grown in Queensland could be graded from highly resistant through to high susceptible, though no immune varieties were found . The level of Pachymetra inoculum in the soil reflects the amount of Pachymetra root rot which has occurred in recent times. The influence of host genotype on the build-up of inoculum in the field, and the degree of resistance required to minimise this inoculum build-up have not been reported. The research reported in this paper investigates the relationship between glasshouse-assigned varietal resistance ratings and the epidemiology of Pachymetra root rot.