h. r. khademhamzeh

Evaluation of the different genotypes under different environmental conditions helps plant breeders in detecting stable and high-yielding genotypes. In this regard, 13 winter rapeseed cultivars and lines were evaluated in a randomized complete block design with three replications in six experimental field stations of cold and temperate regions of Iran (Isfahan, Hamedan, Karaj, Kermanshah, Khoy and Zarghan) during two cropping seasons. For analyzing genotype × environment interactions the multivariate method of additive main effects and multiplicative interaction (AMMI) was used. The Results of combined analysis of variance indicated that 50.26, 4.68 and 23.49 percent of total variation were related to the environment, genotype and genotype × environment interaction effects, respectively. The results showed that the first five principal components of AMMI were significant and described 85.4% of the variance of genotype × environment interaction. Biplot graph of mean seed yield and first interaction principle revealed that genotype G13 had a higher average seed yield than the overall mean yield and lowest value for first principle component. Therefore, this genotype was selected as a high-yielding and stable genotype. Also, Zarghan and Khoy indicated the strongest interactions and, hence, were recognized as the most ideal environments for distinguishing and discriminating winter rapeseed genotypes. The cluster analysis classified the studied environments in three groups. The presence of Isfahan, Hamedan and Zarghan locations each in a group indicates that these locations had the higher predictability and repeatability power compared to other locations. Genotype G13 with mean seed yield of 4086.02 kg ha-1 and a broad adaptability could be used for cultivation in cold and temperate regions of Iran.

Nafis variety (line L72), suitable for cultivation in the cold and moderately cold regions of Iran, is the result of the selection and purification in segregating generations derived from the cross Orient×Modena. Selection of single plants was carried out during five consecutive years using pedigree method until accessing pure lines and then pure lines were screened in F6 generation. Pure lines along with Okapi as check cultivar were evaluated in the preliminary yield trial in experimental farm of Seed and Plant Improvement Institute in 2009. The result showed that mean seed yield of L72 with 3650 kgha-1 was 30.7% higher than Okapi. The study of adaptability of selected lines in Karaj, Hamedan, Zarghan and Kermanshah during 2012-2013 and 2013-2014 showed that line L72 with seed yield of 4137 kgha-1 had the highest grain yield among studies genotypes where its seed yield was 6.7% higher than Okapi and had a good yield stability based on environmental variance statistic. Results of complementary trials for line L72 in Karaj, Hamedan, Zarghan, Isfahan, Khoy and Kermanshah during 2014-2015 and 2015-2016 indicated that this line with grain yield of 4336 kgha-1 had higher yield compared to other genotypes. Field disease assessments indicated high tolerance of L72 to sclerotinia compared to check cultivar Okapi. Results of on-farm trials in farmers' field of Kermanshah province showed that line L72 had 13.7% higher grain yield compared to Ahmadi as check cultivar. Results of on-farm trials in farmers' field of Isfahan province under normal irrigation and irrigation cutting from pod setting stage showed that line L72 had 1.2 and 9.1% higher seed yield than Okapi as check cultivar, respectively. Therefore, due to desirable characteristics of line L72 such as higher seed yield and yield stability and relative tolerance to sclerotinia stem rot compared to Okapi as check cultivar, this line was released as Nafis and is recommended for cultivation in the cold and moderately cold regions of the country.