YIELD LOSSES CAUSED BY PACHYMETRA ROOT ROT IN NORTHERN QUEENSLAND: 10 YEARS OF BREEDING SELECTION TRIAL DATA

PLANT BREEDERS conduct breeding selection yield trials each year as they select the highest yielding clones for consideration as commercial varieties. Only the highest yielding are selected for further testing with very small numbers being released as commercial varieties. Disease susceptibility varies greatly among the tested clones. Routine disease resistance testing is an important aspect of the breeding program. All clones for northern Queensland are screened for Pachymetra root rot resistance while only selected clones from other areas are tested. Analyses were conducted using 10 years of northern Queensland data that related the yielding ability of clones in stage 3 (FAT) trials to Pachymetra resistance. In the 1995–1999 analyses, Pachymetra root rot on average reduced tonnes cane/ha by 14.5% and tonnes sugar/ha by 11.9%; there was a slight positive effect on CCS. Data for 2000–2004 showed smaller losses and this may reflect changes in trial procedures and/or rainfall variation. The data reported here will be valuable for refining selection strategies to improve breeding efficiencies.