Intergenotypic competition in single-row plots of sugarcane variety trials

The early stages of selection in sugarcane variety trials in Australia are usually characterised by a large number of clones with limited replication. Due to the scarcity of seed, establishment costs and the large heterogenous population of clones to be evaluated, small unguarded single-row plots are usually employed for such trials. The importance of competition is well documented in such trials and evidence suggests that ignoring it can seriously bias clonal estimates for single-row plots. Removal of this bias is necessary to obtain a more accurate estimate of how clones will perform when grown under pure stand conditions. In this paper, the bias caused by intergenotypic (inter-plot) competition in single-row plot trials is quantified by a statistical model. Estimates of clonal performance derived from this model arc compared with the mean value of the central two rows of six-row plots. A moderate improvement in the predicted pure stand yield estimates over the unadjusted clonal mean yields resulted from the fit of this model to experimental data. It is recommend that, when evidence of intergenotypic competition is found in single-row plot sugarcane data, adjustments should be made to the clonal effects.