The effect of iron toxicity on some of morphological traits, relative gene expression of G6PDH and peroxidase enzyme activity in resistant and susceptible genotypes of Rice (Oryza sativa)

Under the iron toxicity conditions, one of the most important limiting factors of rice production in agricultural lands is the increase of active oxygen radicals and thus decrease of plant growth and development. In this study, the effect of iron induced toxicity at 0 (control), 100, 250, 400 and 500 mg/l (Fe-EDTA) levels were investigated on some morphological traits, relative expression of G6PDH photosynthetic gene and activity of peroxidase enzyme in two rice genotypes, Pokkali (tolerant) and IR64 (susceptible), at four-leaf growth stage under hydroponic conditions with Yoshida nutrient solution. The experiment was carried out as factorial with two factors, genotype and iron concentration (two and five levels, respectively), in a completely randomized deshgn with three replications. The results showed that the interaction of iron toxicity and genotype had significant effect on all studied traits except root dry weight. Cluster analysis using farthest neighbor divided the ten studied treatments into two separate groups. Principal component analysis showed also that 66% of the total variation was explained by two principal components. Applying iron toxicity stress reduced the relative expression of G6PDH gene in both genotypes, exept that the relative expression of this gene in the Pokkali genotype decreased with the application of low stress levels, but in the IR64 genotype, the decrease in expression of this gene observed only at high stress levels. The lowest activity of peroxidase enzyme was observed in both Pokkali and IR64 genotypes at 100 mg/l iron and the highest activity were observed at 400 and 250 mg/l, respectively. It seems that decreasing the expression of G6PDH gene at low stress levels and increasing the activity of peroxidase enzyme in the tolerant genotype can reduce the amount of hydrogen peroxide induced by iron toxicity.