A Simple Protocol for AMMI Analysis of Yield Trials

The Additive Main effects and Multiplicative Interaction (AMMI) model has been used extensively for analysis of multi-environment yield trials for two main purposes: understanding complex genotype x environment interactions and increasing accuracy. Nevertheless, AMMI analyses implementing best practices have been rare. Accordingly, this paper presents a simple protocol with four steps: (i) analysis of variance, (ii) model diagnosis, (iii) mega-environment delineation, and (iv) agricultural recommendations. This protocol is illustrated with an international bread wheat trial. This paper concerns a basic and common application of AMMI: yield-trial analysis without consideration of special structure or additional data for either genotypes or environments. Best practices involve using both treatment and experimental designs to gain accuracy and exploiting both broad and narrow adaptations to increase yields.