Spatial adjustment in field trend for genotype by environment data analysis of Ethiopian malting barley breeding program

Abstract Food security is the top priority in agricultural policy agendas in Ethiopia, with the goal of feeding the second largest human population on the African continent. To realise this, employing efficient breeding methodologies for selecting stable and high-yielding crop varieties, thereby reducing the confounding effects of the environment and genotype-by-environment interactions for the ultimate deployment of robust new varieties, is a key component of food self-sufficiency. Here, we showed that the application of spatial adjustment to the MET data of a malting barley breeding program enhances selection efficiency and hence contributes to the effective selection of high-yielding varieties. The primary goal of plant breeding programs is to select genotypes for performance across the range of target populations and environments (TPEs) and to conduct multi-environment trials (METs) to aid in genotype selection across targeted locations and seasons. Understanding the pattern of response across these environments is an integral part of superior genotype selection in breeding programs. A set of MET data from the national variety trial series grown across four locations was obtained from the Ethiopian Malting Barley Breeding Program, spanning stages ranging from early generation to the national variety trial. The trials were analysed in a linear mixed model framework fitting a one-stage model for MET data, including a correlated spatial process for field trends within each trial and combining a factor analytic matrix model for genotype-by-environment interaction effects. The genetic correlations from this MET analysis were subsequently used to cluster the four locations based on different response patterns across environments. The stability of genotype performance across these environmental clusters indicated broad and specific adaptation to specific environments. Our analysis revealed that the Holker genotype had a higher average yield than did the other varieties, ranking first in half of the test locations.