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SU MMARYGenotyperenvironment interaction (GEI) is a major factor in the development of stable and highyielding safflower cultivars under rain-fed conditions. In order to quantify GEI effects on the seed yield of 17 safflower genotypes and to identify stable genotypes, multi-environment yield trials (multienvironment trials (MET)) were conducted for four consecutive years in 33 different environments (year-location combinations) during 2003-06. The results indicated that GEI was significant using the Hildebrand (1980) procedure for non-crossover interaction (no change in genotypic rank) and by the Azzalini & Cox (1984) and the De Kroon & Van Der Laan (1981) tests for crossover interaction (change in genotypic rank). The rank-interaction was not significant when assessed using the Bredenkamp (1974) method. Fifteen univariate stability methods measuring different aspects of stability were used to determine stable genotypes. A principal component analysis based on rank correlation matrix separated those methods based on a dynamic concept of yield stability (change in genotypic performance corresponds to the predicted level for each environment) from those which are based on a static one (the lowest changes in genotypic performance across environments). The methods could be grouped into three distinct classes : (i) those which were associated with yield level and the dynamic concept of stability ; (ii) those which were associated with environmental variance, which represents static stability ; and (iii) those which were grouped with non-parametric stability statistics, which also represent static stability. The superiority index of cultivar performance, coefficient of regression, Rank-Sum (sum of ranks of yield and stability variance) and TOP (number of environments at which the cultivar occurred in the top third of the ranks) defined the dynamic stability.In this MET, the genotype PI-537598 was identified as the genotype with the highest yield and high stability of yield.

Partitioning of the genotypes by environment interaction (GEI) is important in order to determine the nature of the GEI. The objectives of this study were to assess the presence and nature of GEI for nine agronomic traits of rapeseed cultivars, and to identify cultivars with favorable levels of stable oil production. Nine rapeseed cultivars, including seven open pollinated and two hybrids, Hyola308 and Hyola401, were grown in ten environments under rain-fed warm areas of Iran. The GEI was significant for all traits and was partitioned into components representing heterogeneity due to environmental index and the remainder of the GEI. Among the all traits with a highly significant heterogeneity, the largest amount of heterogeneity removed from the GEI was for seeds per pod and seed weight. We found GEIs for both oil content and seed yield were largely influenced by differences in correlations among pairs of cultivars (86.8 and 71.4% of the GEI sum of squares, respectively), suggesting that crossover GEIs (i.e., change in genotype rankings among environments) are present. The mean correlation of each cultivar with all other cultivars (" r ii 0 ) ranged from 0.53 to 0.83 for oil content and 0.86 to 0.96 for seed yield. A comparison was done of the significance of Sh-r i 2 (stability variance derived from total GEI) and Sh-S i 2 (adjusted stability variance derived from residual GEI) assignable to each genotype for oil content and seed and oil yield. Based on Sh-r i 2 , three cultivars were unstable for oil content, whereas six cultivars were unstable for seed and oil yield. The removal of heterogeneity revealed that one unstable cultivar for oil content and three unstable cultivars for oil yield were judged to be stable. All cultivars with " r ii 0 B 0.63 were labeled unstable for oil content, whereas all with " r ii 0 B 0.94 were considered unstable for seed yield. The relationships between " r ii 0 and Sh-r i 2 were significant (P \ 0.01) for oil content and seed yield. The results of rank correlation coefficients showed significant positive correlations of Yield-Stability statistic (YS i ) with oil content and oil yield. Cultivars such as Option500 and Hyola401 were identified as having stable, high levels to seed yield and oil content.

Safflower ( Carthamus tinctorius L.) is a native Iranian oilseed crop adapted to various environments in the country. It can be planted as a winter or spring crop. The calculation of drought resistance indices could help us to identify drought-resistant genotypes. To determine these yield-based indices, an investigation was carried out with 16 safflower varieties/lines in spring planting at six research stations located at Sararood, Maragheh, Ghamlo, Zanjan, Shirvan and Kohdasht in 2001. The experiments were laid out in a random complete block design under drought-stressed and non-stressed conditions with three replications. Drought resistance indices, including MP, GMP, TOL, STI and SSI, were calculated from the seed yield data. The genotypes were planted in a greenhouse and the cell membrane stability (CMS) was measured using PEG solutions. Analysis of variance revealed significant differences for all indices between the locations, so experiments should be conducted at different locations over several years for the accurate estimation of drought resistance indices. STI was the best index to identify superior genotypes in conditions both with and without drought stress. The estimation of STI from the mean of all locations showed that Gila had the highest STI (0.430), with high seed yield under both conditions. Analysis of variance showed significant differences between the genotypes for CMS at the 1% level of probability, with the highest value for S-541 and the lowest for Kino-76. There were significant and strong correlations between STI, MP and GMP with CMS, so cell membrane stability could be useful as a fast, cheap method for screening germplasm and identifying drought-resistant genotypes. Cluster analysis on the basis of STI, MP, GMP, CMS and seed yield under both stressed and non-stressed conditions divided the genotypes into three groups.