Enzymatic antioxidant activity and physiological responses of local swamp rice cultivars from Kalimantan-Indonesia under iron toxicity during vegetative stage

Iron toxicity is one of the obstacles to the growth and productivity of local swamp rice. This study aimed to identify iron toxicity-tolerant of local Kalimantan cultivars through their enzymatic and physiological responses. In this study, three Kalimantan local rice cultivars, ‘Amas’, ‘Kambang’, ‘Siam 11 Panjang’ and two control cultivars, ‘Inpara 1’ (iron toxicity-tolerant) and ‘Ciherang’ (iron toxicity-susceptible) were used. Plants were grown in pyrite soil with three different iron concentrations which were 73.85 ppm (low), 114.21 ppm (moderate), and 1383.57 ppm (high) during the vegetative stage. Growth analysis showed that ‘Inpara 1’ had the lowest reduction of plant height, leaf length, leaf width, and leaf number, while ‘Amas’ tended to have tolerant characters with the lowest reduction of root length only. Under high iron levels, the lowest leaf bronzing score was shown by ‘Amas’, while the highest leaf bronzing score was observed in ‘Siam 11 Panjang’. The showed the lowest value of total chlorophyll, chlorophyll a, chlorophyll b, carotenoid and also ascorbate peroxidase activity but with the highest proline level under high iron. Meanwhile, ‘Kambang’ had the lowest reduction of ascorbate peroxidase activity compared to others. ‘Kambang’ also showed tolerant characters as seen in the highest value of superoxide dismutase, ascorbate peroxidase activity, and cell membrane stability index, meanwhile it has the lowest catalase) activity, proline level, and malondialdehyde level under high iron stress. From this study, it can be concluded that ‘Amas’ and ‘Kambang’ are potential candidates for iron toxicity-tolerant rice.