Repeatability and Stability of Agromorphological Characteristics of Onion Cultivars (Allium cepa L.) in the Sudano-Sahelian Zone of Cameroon

Abstract

The variability of environmental conditions leads to significant fluctuations in the agromorphological performance of cultivars. To improve the productivity and stability of varieties, it is essential to assess the repeatability and stability of agromorphological traits. This study evaluates the repeatability and stability of agromorphological traits of onion (Allium cepa L.) cultivars in the Sudano-Sahelian zone of Cameroon. The experiment was conducted at three sites representative of the main onion-producing areas, using a randomized complete block design. Local and improved cultivars were selected based on farmers' preferences, seed availability and climatic conditions. The experimental design included four treatments and three replicates. Excel and XLSTAT (2014.5.02) software were used for treatment analysis. Significant differences between cultivars for each trait were assessed using ANOVA and Fisher's t-test. Statistical analyses of certain traits, such as bulb weight, plant height, and number of leaves, show strong repeatability, suggesting a significant genetic influence. The results show that some traits exhibit strong repeatability (bulb weight: 0.61 and 0.77; plant height: 0.73 to 0.92; number of leaves: 0.74 to 0.83), justifying their use in breeding programs. The Nguetchewé and Palar localities showed good repeatability and genetic stability, suggesting the implementation of a breeding program or the creation of a new variety. However, the repeatability of the "plant height" trait in the different localities shows     relatively low values: 0.30, 0.16, and 0.17. The low repeatability observed in some locations therefore limits the accuracy of selection based solely on plant height. Conversely, the repeatability value of 0.52 for this trait indicates a certain consistency in the genetic expression of plant height in at least one environment, allowing for moderate selection. The Nguetchewé, Palar, and Pitoa sites show repeatability and stability results deemed satisfactory for certain important traits (bulb weight, flower peduncle), making them priority areas for varietal selection and onion seed production. Plant height remains a trait with low overall repeatability: its selection is only effective in a controlled environment and should preferably be combined with other, more stable criteria.