Optimal plot size and replication for testing clones in early stages of selection : SRDC final report CSR017

Abstract

The aim of CSRO 17 was to identifY optimal plot design, replication and selection criteria for testing and selecting clones in small plots in early stages of selection in sugarcane breeding programs. Problems associated with the use of small plots are well known in field experimentation. This is particularly so in variety selection trials where measurements in small plots are subject to possible bias due to competition effects when there are significant differences in height between genotypes being compared. In sugarcane breeding programs, small, single row or two row plots are usually used extensively for the first two stages of selection within seedling populations. The reasons for this include the desire to screen large populations of clones within available resource constraints to identifY rare, elite recombinants, and the necessity to bulk up planting material from original seedlings before planting to larger plots. Given the level of resources usually devoted to early stage selection trials, it is important that optimal procedures are used so that selection is effective and efficient. The overall approach used in the project was to obtain estimates of key genetic parameters from field experimentation and then to use these to predict gains from selection among relatively unselected clonal populations in sugarcane breeding programs using different selection options. The clones used in this study were representative of those directly derived from hybridisation in two different sugarcane breeding programs, and were unbiased by any previous selection. As such, the genetic parameters are useful for other studies that may simulate and assess different options for selection from the first stages of selection in sugarcane breeding programs.