ASSESSMENT OF GENOTYPE BY ENVIRONMENT INTERACTIONS AND GRAIN YIELD PERFORMANCE OF ESWATINI MAIZE (Zea mays L.) LANDRACES
Maize (Zea mays L.) is one of the important commercial crops of the world. Beside its uses as food and feed, maize is a priority and strategic crop to respond to the world’s pursuit for alternative energy sources. In Eswatini, it ranks first in total production and yield per unit area and it is the staple crop for the majority of Swazis, especially those in rural areas. It is grown by both large-and small-scale farmers in the different agro-ecological zones of the country. The decision to recommend and distribute high yielding and adapted maize cultivars to these agro-ecological zones involves conducting multi-environment trials (METs) to identify the best cultivar across locations and years. Seventy (70) diverse maize landraces (accessions) conserved ex situ at the National Plant Genetic Resources Centre (NPGRC) were evaluated across three (3) locations during the 2016/2017 and 2017/2018 cropping seasons. The objectives of the study were to determine the extent and nature of genotype-by-environment interaction (GEI) on grain yield based on analysis of variance (ANOVA) procedures and to identify landraces that are specifically or widely adapted. The combined ANOVA indicated that the mean squares for landraces (G), years (Y), environments (E) and all interactions were all highly significant (P 0.01) on grain yield. Landraces, environments and years explained 26.35, 32.08 and 15.66% of the total treatment variance respectively, whilst GEI accounted for 7.78%. Crossover type of GEI was observed in all evaluated landraces and based on mean grain yield across locations and years, accessions M258, M17 and M251 had the highest mean grain yields of 6.49, 6.39, 6.38 t ha-1 respectively. A stability analysis based on univariate or multivariate parameters is further recommended to extract more information on the GEI.