Genotype and Management Evaluation Based on Genotype by Yield*Trait (GYT) Analysis

Data for multiple traits are routinely collected in crop variety trials and agronomic management studies, which are used to identify superior genotypes, managements, or genotype-management combinations for a given crop and region. However, dealing with multiple traits has been a challenge due to unfavourable associations among traits. In this paper we demonstrate the use of GYT (genotype by yield*trait) analysis for evaluating genotypes (or agronomic managements or genotype-management combinations) based on multiple traits. Genotype evaluation using GYT analysis involves several steps. First, convert the genotype by trait two-way table into a GYT table. Second, standardize the GYT table by each yield-trait combination. Third, apply proper weights to the yield-trait combinations according to their relative importance. Finally, calculate the GYT index, which is the mean across weighted yield-trait combinations for each genotype. The GYT index is a measure of the overall superiority and can be used to rank the genotypes. The GYT index is superior to traditional selection index because it is based on the concept that yield is the most important trait and the economic value of a level of other traits increases with the yield level it is combined. Selection based on the GYT index can prevent low-yielding genotypes from being selected and recommended. GYT analysis can be greatly assisted by the use of GYT biplot, which graphically ranks the genotypes on their overall superiority and shows their strengths and weaknesses. Agronomic managements and genotype-management combinations can be evaluated similarly. Multiple trait data from an oat (Avena sativa L.) management study involving three cultivars, four N-fertilizer treatments, and two fungicide treatments, conducted in northern Ontario in 2015 and 2016, were used to demonstrate GYT analysis