Dithizone Screening Protocol to Select Promising Rice with High Grain Zinc Content

Estimation or screening of grain zinc (Zn) content is essential for Zn biofortification studies. However, the required sophisticated equipment and human resources are available only in some laboratories of India. Therefore, this study aimed to standardize the conditions to use Dithizone (DTZ) stain to select high grain Zn rice through naked eye for the benefit of the researchers and stakeholders interested to estimate Zn content in rice grain. Various concentrations of DTZ (1 mg/ml to 0.17 mg/ml methanol) were tried in various volumes (25 µl to 100 µl) on intact polished grain, longitudinal sections and varying quantities (25 mg to 100 mg) of polished rice powders. Clear differentiation in intensity of the stain was not observed for both intact polished grain and its longitudinal sections. The combination of 100 mg polished rice powders along with 100 µl of DTZ stain (0.34 mg/ml) was found useful to categorize rice samples as above or below threshold level (24 mg/kg) of grain Zn content with 70 % accuracy in 15 minutes incubation time. The study reports a rapid, simple and inexpensive staining method for rapid screening of rice germplasm for grain Zn.