A B Supplementary Figure S1: Standard evaluation score of susceptibility to iron toxicity, attributed to genotypes in the field, ranging from 1 (tolerant) to 10 (extremely sensitive). The rice varieties screened on an iron toxic acid sulfate soil in San Anonio, City of Ajuy, Visaya Islands, Philippines. The experiment was conducted from June to October 2013. Seeds were sown directly on to the raised seedbed. The field was prepared with NPK fertilizer to avoid toxicity symptoms due to lack of other nutrients. Rat and bird protection was set up. Insecticide was applied as per local farmers practice. The field was hand-weeded. Plants were transplanted after 26 days, following a randomized complete block design (RCBD) with three replicates. Each replicate consisted of 81 plants (three rows x 27 hills). As the outer plants were not considered for harvest, 25 hills x three rows accounted for a 3 m2 plot size. Yield data are not available because the experiment was devastated by the typhoon ‘Yolanda’ before harvest. Genotypes included in the greenhouse experiment described in the main article are marked by arrows. Photograph of Dom Sofid growing in the field experiment described above. A B