Resource allocation in Maritime cereal cultivar trials

Abstract

Research funding for cooperators in the cereal cultivar testing system in Canada is declining, and cooperators are under pressure to reduce their testing effort. The impact of reducing the number of years, test sites, and replications on the standard error of cultivar means (SE), predicted response to selection (R), and the probability of accepting inferior cultivars in Maritime spring cereal registration trials was examined using variance component estimates. Reducing the number of replications increased SE less than reducing the number of sites or years of testing. Reducing replicates per site from four to two increased SE by no more than 0.02 t ha−1 when the number of sites was three or more. Reducing the number of trial sites from five to three, however, increased SE by up to 0.06 t ha−1 and reduced R by as much as 16%. The probability that a cultivar with a true yield 5% less than that of a standard would equal or exceed the standard in a 3-yr series of trials conducted at five sites ranged from 6% in 2-row barley to 21% in winter wheat. Cost reductions in the Maritime cereal registration trials should be achieved, where possible, by reducing within-site replication rather than reducing the number of trial sites. Some reduction in the risk of registering inferior cultivars can be achieved by comparing test cultivars with the mean of several standards, rather than with a single standard. Key words: Replication, genotype × environment interaction, selection response, acceptance probability, variance components, residual maximum likelihood