Assessment of seed yield stability of spring oilseed rape (Brassica napus L.) promising lines using GGE-biplot analysis

Genotype by environment interaction is one of the complicated issues in plant breeding programs for development of high-yielding with yield stability genotypes. To evaluate seed yield and yield stability of oilseed rape in four southern and northern warm regions of Iran (Zabol, Gorgan, Haji Abad and Sari), nine open pollinated spring oilseed rape lines together with seven cultivars were evaluated using randomized complete block design with three replications in two cropping cycles (2017-19). The results showed that G9 (SRL-95-16) and G12 (OG-AL) genotypes had the highest and the lowest seed yield with mean seed yiled of 3412 and 2507 kg.ha-1, respectively. In this study, seed yield wassignificantly different in different environments. The genotype × environment interaction was investigated using GGE-bioplot stability analysis. According to the which-won-where model of the GGE-biplot model, most of the studied environments were located in or close to the mega-environment 2 which included genotypes G2 (SRL-95-7) and G9 (SRL-95-16) as the best genotypes in this mega-environment. Also, the study of the average tester coordinates showed that G2 and G9 genotypes as superior to all check genotypes like G11 (Dalgan which ranked third) and as the best genotypes considering both seed yiled and yield stability. Also, these two genotypes had the shortest distance from the hypothetical ideal genotype in comparison with other lines and check cultivars. Therefore, considering seed yield and its stability, two genotypes G9 and G2 were identified as suitable genotypes for the southern and northern warm regions of Iran.