AMMI model in the analysis of genotype by environment interaction of conventionally and organically grown onion

This study was aimed to assess the stability of direct yield components (bulb weight and number plot-1) and other yield contributing characteristics (bulb diameter, height and index, neck diameter and length, plant height, emergence and vegetation period) in five commercial onion cultivars grown in conventional and organic environments, by employing additive main effect and multiplicative interaction (AMMI) statistical model in data analysis. The two-year field trial organized in complete randomized blocks included the plots maintained in four regimes: mineral fertilization (conventional), without fertilization, fertilization with farmyard manure and with bacterial fertilizer (organic). Each treatment by year combination was considered as an environment. Analysis of variance of AMMI model calculated for the investigated traits showed that all sources of variation (genotypes, environments, genotype by environment interaction) were highly significant. The largest proportions of the total sum of squares were encompassed by environments, except for emergence and bulb index with the pronounced effect of genotypes (67.26 and 52.54%, respectively) and neck length with the genotype by environment interaction amounting 44.59%. Generally, the effects of the interactions were in the common range. The AMMI model with two axes was concluded as the best model for the investigated traits. Onions grown in conventional system outperformed the organic ones. However, good performance of the genotypes was accompanied with low stability across the environments and vice versa. Therefore breeding programs intended to develop cultivars adapted to alternative production systems should rely on the experiments set in the corresponding environments that include various combinations of genotypes and agro-technical procedures based on the principles of organic agriculture.