Iron Toxicity Tolerance of Improved Rice Varieties in the Low Country Wet Zone of Sri Lanka

Abstract

In order to evaluate the impact of iron rich adverse soil on the improved rice varieties of Sri Lanka, a field experiment was carried out, in two seasons of 2012/13 Maha and 2012 Yala. Thirty seven improved rice varieties were tested in this study. Extractable soil iron (Fe) level of tested locations varied from 245ppm to 326ppm during the evaluation period. Design of the experiment was an augmented method with two replicates for each entry and rice plant reactions for Fe toxicity were evaluated by using the IRR1 standard evaluation system. Among the tested rice varieties, two varieties (Bw 267-3, Bw 367) performed as highly Fe tolerant varieties and twelve varieties (Bw 451, Bg 360, Bg 406, Bw 364, At 354, Bg 358, Bw 363, Bg 379-2, Bg 359, Bg 454, Bg 250, Bg 96-741) were recorded to have field level of tolerance. Twenty rice varieties were moderately tolerant (Bg305, Bg 357, Bg 403, Bw 361, Bg 94-1, Bg 3-5, At 308, Ld 408, Bw 452, Bw 453, Bw 351, At 307, At 303, Ld 365, At 362, Bg 38, Bg 300, Bg 745, Bg 450, Ld 368) and three rice varieties (Bw 272-6b, Bg 407 and At 303) were highly susceptible. Variations of rice varietal reactions were observed during the stress period where highly tolerant varieties grew normally without leaf bronzing symptoms, tolerant cultivars remained green until later stage of plant growth (88 days) while moderately tolerant varieties developed leaf bronzing symptoms at least once in the growth period especially at panicle initiation and susceptible varieties had prominent leaf bronzing symptoms throughout the evaluation period.