THE RELATIONSHIP BETWEEN GLASSHOUSE AND FIELD-DERIVED RESISTANCE RATINGS FOR PACHYMETRA ROOT ROT

PACHYMETRA root rot varietal resistance screening is an important component of the Pachymetra disease management program. Resistance ratings for varieties are derived from glasshouse pot trials. The relationship between these resistance ratings and the field reaction of each variety is critical for ensuring effective disease control in the field. In the late 1980s, six field trials were planted in northern Queensland that incorporated almost all the standard varieties currently used in the glasshouse resistance screening trials. Field resistance ratings were applied to these varieties based on Pachymetra spore population changes beneath each variety after a plant and first ratoon crop. Field resistance ratings were correlated with glasshouse-applied ratings generated from three previously reported screening methods (here termed ‘previous ratings’, ‘revised % rot’ ratings and ‘Quikrat’ ratings). The ‘revised % rot’ and the ‘Quikrat’ data gave the best correlation with field data. There was a high correlation between all three glasshouse methods and field ratings suggesting that the glasshouse resistance-screening test has provided very useful resistance ratings for clones within the BSES selection program.