Investigation the Yield Stability of Brassica Genotypes (Brassica spp.) under Drought Stress by using Statistical Parameters and GGE Biplot Graphical Methods

Water stress particularly during the end of crop growing season causes a great yield loss in the production of oilseed rape (Brassica napus L.) in Iran. Researchers emphasize on the use of stable and water stress tolerant genotypes to alleviate the impact of water stress on the crop yield.

In order to identify high yielding and stable oil brassica genotypes under drought stress a total of 24 genotypes from three brassica species of Brassica napus, B. rapa and B. juncea, were studied in two moisture conditions (normal and drought stress) in a randomized complete block design for two years in one location; seed and plant improvement institute. Each genotype was planted in a 6-square meter plot and irrigated at different plant growth stages including planting time, seedling establishment, stem elongation, flowering and seed filling. To apply water stress, irrigation was not implemented at seed filling stage. At full maturity, two middle rows of each plot were harvested and seed yield were measured. Following simple and combined data analyzing of variance, univariate statistics, regression coefficient, deviation from regression parameter, Shukla’s stability variance, and Wricke’s ecovalence were used to evaluate the grain yield stability of genotypes. Finally, GGE-biplot analysis was used to better interpret the interaction of genotype with environment.

The results showed that seed yield is largely influenced by environmental factors. Based on all stability parameters and biplot analysis, genotypes no. 4, 6, 8 and 10 from B. napus with mean yield of 2725, 2820, 3079 and 2729 kg/ha had higher yield than total mean, lower Wricke’s ecovalence and Shukla’s stability variance, regression coefficient equivalent to one and low deviation from regression parameter, therefore, selected as the most stable genotypes. Furthermore, genotypes no. 3 and 17 form B. napus and no. 23 (BP.18) from B. juncea with mean yield of 2660 and 2751 kg/ha showed moderate yield stability. In terms of mean yield in whole environments, line no. 23 from B. juncea with 2958 kg/ha ranked third after line no. 8 and 16 from B. napus with mean yield of 3079 and 3071 kg/ha.

Although line no. 8 from B. napus has a high yield and stability, the results of this study also implies that line no. 23 from B. juncea relatively has a good stability and performance under water stress and normal condition. Species B. juncea generally has some good agronomic characteristics such as resistance to drought, seed shattering, and pests and have early maturity that could be introduced to regions with drought stress condition.