Development and Standardization of a Simple and Quick Screening Protocol for Arsenic Phyto-toxicity Tolerance at Seedling Stage in Rice

Cultivation with Arsenic (As) contaminated water severely affects growth of rice plants that results into reduced grain yield. This study was carried out to develop a rapid and effective method of screening rice varieties and/or segregating population against arsenic phyto-toxicity tolerance. Sodium arsenate was used as arsenic source. Ten pre-germinated seeds of each variety were grown on styro-foam placed on a tray filled with either phosphate-free nutrient solution (control) or the same nutrient solution supplemented with di-sodium hydrogen arsenate (treatment). The trays were kept at controlled environmental condition in a growth chamber at 26±1℃ with 70% humidity and 3500 lux. After 7 days of growth, standard growth parameters such as shoot length, root length, root-shoot biomass were recorded and percentages reduction for shoot length, root length and root shoot biomass compared to those of control were calculated. Arsenic stress reduced the phenotypic expression of all three seedling traits but the effect of arsenic was more prominent on root length compared to the shoot length and root-shoot biomass. The dose response experiment showed that the 0.75-1.25 mgL-1 Arsenic concentrations had much promise to discriminate rice genotypes for arsenic phyto-toxicity tolerance at early growth stage. The validation experiment with the 0.75-1.25 mgL-1 Arsenic doses on a set of 20 genotypes identified 1.25 mgL-1 Arsenic could effectively and efficiently differentiate rice genotypes, particularly for tolerance in shoot length and root-shoot biomass reduction, where 1.0 mgL-1 Arsenic was found sufficient for discriminating varieties for tolerance in root length reduction. The rice variety BRRI dhan47 showed more tolerance against Arsenic contaminated water.