Communications in Soil Science and Plant Analysis, 45:2932–2948, 2014 Copyright © Taylor & Francis Group, LLC ISSN: 0010-3624 print / 1532-2416 online DOI: 10.1080/00103624.2014.954720 Genotypic Divergence in Expression of Zinc-Deficiency Symptoms of Rice (Oryza sativa L.) in Sand Culture C. SUDHALAKSHMI, R. KRISHNASAMY, A. RAJARAJAN, AND S. MEENA Department of Soil and Environment, Agricultural College and Research Institute, Tamil Nadu Agricultural University, Madurai, Tamil Nadu, India Zinc (Zn) deficiency is a ubiquitous disorder constraining rice production world- wide. A sand culture experiment was conducted in factorial randomized block design with three replications to study the relative performance of 18 rice (Oryza sativa L.) genotypes experiencing Zn stress. Modified Hoagland’s solution was employed as the nutrient medium and the experiment was maintained for 60 days from sowing. The genotypes were categorized as efficient (Norungan, ASD 16, Pokkali, Pusa Vikas, TRY 1, and Triveni), moderately efficient (White Ponni, CO 47, ADT 36, IR 8, ASD 20, and TRY 2), and inefficient (ADT 38, PMK 3, CO 43, CSR 10, ADTRH 1, and MDU 5) to Zn stress based on the preliminary solution culture experiment (Sudhalakshmi 2007). Growth performance, dry-matter production, biochemical constituents, and enzymatic activity of rice were measured employing graded levels of Zn (at 0, 0.025, 0.05, 0.1, and 0.2 mg L -1 ) and were statistically analyzed using the method of Panse and Sukhatme (1978). The efficient rice genotypes showed minimum reduction in dry-matter produc- tion in Zn stress conditions while the inefficient rice genotypes suffered severe reduction. Zinc-efficient rice genotypes were not responsive to fertilizer. Dry-matter production, chlorophyll a, chlorophyll b, total chlorophyll, soluble protein, and indole-3-acetic acid (IAA) oxidase activity can be employed as diagnostic tools to differentiate Zn-efficient and Zn-inefficient rice genotypes in sand culture. Keywords IAA oxidase activity, Oryza sativa L., soluble protein, zinc efficient, zinc stress Introduction Zinc (Zn) is an element required virtually by all organisms, as it is a critical component of many enzymes and proteins (Marschner 1995). It is estimated that approximately 50% of soils used for cereal production in the world have low levels of plant-available Zn (Graham and Welch 1996). Zinc deficiency depresses rice production on more than 2 mil- lion hectares in Asia (Ferno, Yoshida, and Ahser 1970), which is both an economic and a humanitarian problem. Zinc deficiency is common in a wide range of soil types, including calcareous soils of high pH, sandy soils, and high phosphorus-containing soils (Marschner 1995). Unlike the other micronutrients, Zn deficiency is a common feature of both cold and Received 10 July 2012; accepted 23 April 2014. Address correspondence to C. Sudhalakshmi, Department of Soil and Environment, Agricultural College and Research Institute, Tamil Nadu Agricultural University, Madurai 625 104, Tamil Nadu, India. E-mail: soilsudha@yahoo.co.in 2932