Abstract
Replicated multi-location yield trials are conducted every year in all regions throughout the world for all regionally important crops. Heritability, i.e., selection accuracy based on variety trials, improves with increased number of replicates. However, each replicate is associated with considerable cost. Therefore, it is important for crop variety trials to be optimally replicated. Based on the theory of quantitative genetics, functions that quantitatively define optimal replication on the single-trial basis and on multi-location trial basis were derived. The function on the single-trial basis often over-estimates the optimum number of replicates; it is the function on multi-location trial basis that is recommended for determining the optimal number of replicates. Applying the latter function to the yield data from the 2015–2019 Ottawa oat registration trials conducted both in Ontario and in other provinces of Canada led to the conclusion that a single replicate or two replicates would have sufficed under the current multi-location trial setup. This conclusion was empirically confirmed by comparing genotypic rankings based on all replicates with that on any two replicates. Use of two replicates can save 33–50% of field plots without affecting the selection efficacy.
Highlights
Crop variety trials are one of the best funded agronomic studies in the world
The estimated trial heritability (Eq 1), the optimum number of replicates for each trial (Eq 3), the mean trial heritability, and the mean required number of replicates averaged across locations each year are presented in Table 2; results for trials within Ontario and those in other provinces are analyzed and presented separately
coefficient of variation (CV) is a measure of trial accuracy independent of genotypic variation while heritability is a measure of both trial accuracy and trial usefulness to genotype valuation (Yan, 2014).These two trials were considered as failed and were excluded from calculating the yearly means
Summary
Crop variety trials are one of the best funded agronomic studies in the world. Regardless of social and economical levels, crop variety trials are conducted every year in every region for every regionally important crop, to provide information to growers on the performance of existing cultivars and to breeders for releasing new cultivars. For a test of 30 entries at 10 locations with four replicates, the cost would be $48000–60000. This amount increases quickly when multiplied with the number of tests, crops, breeding institutes, regions, and years. It is of great economical value to minimize the number of plots while maintaining trial efficacy
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