Evaluation of yield stability of promising winter rapeseed lines in cold and semi-cold climate of Iran

Rapeseed (B. napus. L) is the most important and most cultivated area among other oil crops in Iran. Two types of it, spring and winter, are cultivated in the country. More than 70% of rapeseed is cultivated in semi-hot and tropical regions and only 30% in cold and semi-cold areas of Iran. Considering the dependence of more than 90% of the country on oil imports and the importance of producing oilseeds, it seems necessary to pay attention to the appropriate cultivars in semi cold and cold regions and use the existing potential to develop its oilseed cultivation. Therefore, in this study, the stability of rapeseed winter mutant lines was investigated.

In this study, three Rapeseed cultivars named Zarfam, Talaieh and Express, along with 16 mutant lines, were obtained from irradiating the above cultivars with intensities of 800-900-1200 g of gamma-ray and, after seven generations, were salved. Along with three commercial cultivars, Okapi, Ahmadi and ES Neptune, they were planted in a randomized complete block design with three replications. This experiment was carried out in four research stations (Karaj, Zarghan, Kermanshah and Isfahan) during the two crop years of 2015-2016 and 2016-2017. In the combined analysis, the effect of environment (year composition on location) was considered random, and the effect of genotype was fixed. The stability of the lines was performed by AMMI method, Stability value (ASV) statistics and other stability methods include S (1-6), NP (1-4), etc.

The Combined analysis of data showed that the effect of genotype, environment and genotype × environment interaction were significant at the 1% level probability and explained 7.5, 55.3 and 37.0% of the total variance of the data, respectively. In this study, genotype × environment interaction was divided into four components, which accounted for 36.7, 23.6, 16.5, and 9.7% of the total interaction squares, respectively. This study's results showed a high genetic diversity between mutant lines evaluated in terms of grain yield.G13 (T-900-4) lines, followed by G6 (Z-900-7), and G3 (Z-800-6) were superior to other lines in grain yield, averaging 3840, 3757 and 3665 kg/ha, respectively. In the biplot diagram of grain yield and ASV index, lines G3, G6, G2, G18 and G7 had the highest yield and the lowest number for ASV, which were identified as stable lines.

The results of the Three-dimensional graph of the mean rank of stability statistics (Ar) and standard deviation of rankings (SD), and mean yield showed that lines G6 (Z-900-7), G2 (Z-800-3), G12 (T-800-6) and G15 (T-1200-1) were stable line with higher-than-average yield and control cultivars of the region and were identified as stable lines.