SUMMARY
Some improved irrigated lowland rice varieties are quite adaptive to tidal swamp areas where iron stress is the limiting factor of productivity. Information on irrigated rice tolerance to iron toxicity is inadequate and digital image processing for determining the level of tolerance is not available. The study aimed to evaluate tolerance of irrigated rice to iron toxicity. Ten irrigated rice varieties were used, namely Inpari 3, Inpari 19, Inpari 22, Inpari 24, Inpari 32, Inpari 42, Inpari 47, Inpari IR Nutri Zinc, Cakrabuana Agritan and Inpago 13 Fortiz. Mahsuri is tolerant and IR 64 is a sensitive check. The seedlings were planted on Yoshida agar solution using a randomized completely block design with four replications. Leaf bronzing symptoms showed that Inpari 47 was tolerant (score 2), Inpari 3 and Inpari 42 were moderately tolerant (score 4), Inpari 19 and Inpari 22 were also moderately tolerant (score 5). The bronzing symptom based on image processing has a strong correlation with visual observation, leading to propose that image processing is an alternative method to determine the bronzing symptom. Inpari 47 absorbed quite a lot of Fe with few bronzing symptoms. Inpari IR Nutri Zinc absorbed less Fe, but had more symptoms than Inpari 47. Inpari 19 had a longer shoot, while Inpari 42 and Inpari 47 had longer roots. Based on this study, Inpari 47 can be recommended for moderate iron stress-prone areas, meanwhile, Inpari 3, Inpari 42, Inpari IR Nutri Zinc, and Inpari 32 HDB for low iron stress-prone areas.