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Addressing the Dilemmas of Measuring Amylose in Rice

¹International Network for Quality Rice, IRRI, Los Banos, The Philippines. ²Grain Quality, Nutrition and Postharvest Centre, International Rice Research Institute, DAPO 7777, Metro Manila, Philippines. Corresponding author. Phone: 632 580 5600. Fax: 632 580 5699. E-mail: m.fitzgerald@cgiar.org ³Department of Food and Beverage, University of Nevada-Las Vegas, Las Vegas, NV 89154, United States. ⁴FOSS Analytical AB, Höganäs, Sweden. ⁵Yanco Agricultural Institute, NSW Department of Industry and Investment, PMB, Yanco, 2703, NSW, Australia. ⁶Rice Research Program, National Agricultural Research Institute, INIA Treinta y Tres, Ruta 8 km 281, Treinta y Tres, CP 33000, Uruguay. ⁷United States Department of Agriculture, Agricultural Research Service, Rice Research Unit, 1509 Aggie Drive, Beaumont, TX 77713, United States. ⁸Laboratorio de Calidad FLAR-CIAT, CIAT, Km 17 via Cali-Palmira, Colombia. ⁹Rice Chemistry and Food Science Division, Philippine Rice Research Institute, Maligaya, Science City of Muñoz, 3119 Nueva Ecija, Philippines. ¹⁰Rice Research Institute of Iran (RRII), 41996-13475 Rasht, I.R. Iran. ¹¹Rice Quality Research Team, National Institute of Crop Science, Tsukuba, Ibaraki 305-8518, Japan. ¹²Ubonratchathani Rice Research Centre, Thailand. ¹³Fundación para la Investigación Agrícola DANAC. Apartado Postal 182, San Felipe, Estado Yaracuy, Venezuela. ¹⁴Rice Research & Development Centre, R & D Unit of Tilda Riceland Pvt. Ltd., 2633, II Main, V. V. Mohalla, Mysore – 570002 India. ¹⁵Embrapa Arroz e Feijão, Rodovia GO-462, Km 12, Zona Rural, C.P. 179 Santo Antônio de Goiás – GO, 75375-000, Brasil. ¹⁶Department of Rice, Centre for Plant Breeding and Genetics, Tamil Nadu Agricultural University, Coimbatore 641 003, Tamil Nadu, India. ¹⁷Crop Improvement Section, Directorate of Rice Research, Rajendra Nagar, Hyderabad 500030 AP, India. ¹⁸Division of Biochemistry, Central Rice Research Institute, Cuttack-753006 (Orissa) India. ¹⁹Department of Food Science, University of Arkansas, Fayetteville, AR 72704. ²⁰Indonesian Center for Rice Research (ICRR) BB Padi, Jl. Raya 9, Sukamandi, Subang 41256 Jawa Barat Indonesia. ²¹Pusat Penyelidikan Padi dan Tanaman Industri, MARDI Seberang Perai Beg Berkunci 203 Pejabat Pos Kepala Batas, 13200 Seberang Perai Pulau Penang, Malaysia. ²²Rice Programme, National Agricultural Research Centre, Islamabad, Pakistan. ²³Grain Quality and Nutrition Division, Bangladesh Rice Research Institute (BRRI), Gazipur 1701, Bangladesh. ²⁴China National Rice Research Institute, Hangzhou, China. ²⁵Genetic & Plant Breeding Division, Cuulong Delta Rice Research Inst., Viet Nam. ²⁶College of Home Science, G.B.P.U.A & T University, Pantnagar 263145, U.S. nagar, Uttrakhand, India. ²⁷Programa Nadional de Arroz. Instituto de Investigaciones del Arroz. Depart. Tecnología Postcosecha. Km 16 1/2 Autopista del Mediodía. Apartado Postal. Bauta. La Habana. Cuba. ²⁸CIRAD, Performances des Systèmes de Production et Transformation Tropicaux UMR Qualisud, TA B-95/16 73 avenue JF Breton, 34 398 Montpellier Cedex 5, France.

Amylose content is a parameter that correlates with the cooking behavior of rice. It is measured at the earliest possible stages of rice improvement programs to enable breeders to build the foundations of appropriate grain quality during cultivar development. Amylose is usually quantified by absorbance of the amylose-iodine complex. The International Network for Quality Rice (INQR) conducted a survey to determine ways that amylose is measured, reproducibility between laboratories, and sources of variation. Each laboratory measured the amylose content of a set of 17 cultivars of rice. The study shows that five different versions of the iodine binding method are in use. The data show that repeatability was high within laboratories but reproducibility between laboratories was low. The major sources of variability were the way the standard curve was constructed and the iodine binding capacity of the potato amylose used to produce the standard. Reproducibility is much lower between laboratories using a standard curve of potato amylose alone compared with those using calibrated rice cultivars. This study highlights the need to standardize the way amylose is measured, and presents research avenues for doing so.