Background The main objectives of this study were to find the possible structural association between the activity of enzymatic antioxidants and the grain yield of triticale plants as well as identifying the genotypic variability which might be effective on this association. Accordingly, expression levels of superoxide dismutase (SOD) isozymes (Mn-SOD, Cu/Zn-SOD, and Fe-SOD) were appraised to distinguish any possible relationship between SOD expression and drought resistance of triticale. A novel analytical method for distinguishing elite genotypes based on measured features was proposed. Additionally, a new programing based on SAS-language (IML) was introduced to estimate the genetic parameters rooted from combined ANOVA model (linear mixed model), which is capable of being used in any field study other than the current one. Methods Thirty genotypes of triticale were studied under normal and drought stress conditions during 6 years (three different locations). Accordingly, based on the results of genetic variability, heatmap analysis, biplot graph, and clustering technique, two genotypes with the highest genetic distance were selected to appraise the differential expression profiling of three SOD isozyme in shoot and root organs. Results Field experiments and bioinformatics results showed that superoxide dismutase (SOD) was the most influential antioxidant in resistance of triticale to drought stress; therefore, it could be used as an indirect selection index in early stages to distinguish resistant genotypes to drought stress. Additionally, Mn-SOD and Fe-SOD showed roughly similar expression levels for both genotypes under drought stress. However, Cu/Zn-SOD expression level was higher in root and shoot of the tolerant genotype than the susceptible genotype. Conclusion Heatmap analysis that is applied for the first time to screen suitable genotypes, showed to be highly capable of distinguishing elite genotypes and pointing out the proper features for selection criteria. Bioinformatics results indicated that SOD is more important than other enzymatic antioxidant for being considered as selection criteria or candidate gene for transgenic purposes. Based on expressional results, Mn-SOD announced as a general isozyme that is probably highly expressed in most of the species, while, Cu/Zn-SOD was introduced as a genotype specific isozyme that is likely more expressed in tolerant genotypes

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BackgroundThe main objectives of the current study were to find the possible structural association between the activity of enzymatic antioxidants and grain yield of triticale plants along with identify the genotypic variability of SOD activity among different triticale elite genotypes using novel statistical methods. Additionally, the difference between expression rate of SOD isozymes (Mn-SOD, Cu/Zn-SOD, and Fe-SOD) were tested to find out about the relationship between expression rate and the drought resistance of triticale selected genotypes. The final goal of this study was to introduce source code in SAS language to estimate the genetic parameters based on combined ANOVA model that could be applicable in all field studies.MethodsThirty genotypes of triticale were studied during six years in three different locations to model the relationship of enzymatic antioxidants and grain yield under drought stress condition. In every year, two separate field trials were used to assess the effect of normal irrigation (irrigation trial) and drought stress conditions (stress trials) by withholding irrigation at early heading stage. Accordingly, based on the results of genetic variability, heatmap analysis, biplot graph, and clustering, two genotypes with the highest genetic distance were selected to appraise the differential expression profiling of three SOD isozyme in shoot and root organs.ResultsField experiments and bioinformatics results showed that superoxide dismutase (SOD) was the most influential antioxidant in triticale tolerance to drought stress. Additionally, Mn-SOD showed high expression levels for both genotypes but with higher rates in tolerant genotype. Also, Mn-SOD expression rate in shoot was higher than root, but the expression level of Fe-SOD was conversely higher in the root. Additionally, Fe-SOD expression levels showed no significant difference in two used genotypes. The expression level of Cu/Zn-SOD was higher in root of the tolerant genotype while lower in root of susceptible genotype, as compared with their shoot.ConclusionHeatmap analysis that is applied for the first time in a screening program, showed to be highly capable of distinguishing elite genotypes and pointing out the proper features for selection criteria. Bioinformatics results indicated that SOD is more important than other enzymatic antioxidant for being considered as selection criteria or candidate gene for transgenic purposes. Based on expressional results, Mn-SOD announced as general isozyme that probably is highly expressed in most of the species, while, Cu/Zn-SOD as was introduced as a genotype specific isozyme that is likely more expressed in tolerant genotypes of triticale.

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