Molecular Characterization of Diverse Rice (Oryza sativa L.) Genotypes for Glycemic Index

Abstract

The Glycemic Index (GI) of food is a measure of the rate at which glucose is released after consuming a specific amount and is important in diabetes management. The GI and digestibility of rice starch depends upon its amylose content and structure. The aim of current study was to asses GI of diverse genotypes and validate their association with GI linked marker. Considering the availability of diverse rice genotypes and their genetic variability, sixteen different rice genotypes/lines which includes six inbreed lines and four improved varieties developed by ICAR-Indian Institute of Rice Research Hyderabad and six genotypes from local market were screened for biochemical quality trait viz., amylose, carbohydrate, resistant starch along with glycemic index. The amylose content observed over the varieties ranged from 10.12 % to 62.58 %. Carbohydrate content ranged from 83.08 % to 86.33 % with the mean of 84.87 and resistant starch content varied from 1.75% to 5.34 % with the mean of 3.52. Glycemic index of selected rice varied from 52.40 to 137.06 with general mean of 83.33. In our study significant variation was observed among all varieties except carbohydrates. Among all varieties, CSR23 has significantly higher GI (137.06) and rice inbreed lines serially numbered as 84, 87, 97, 6-5 and 128 have shown significantly lower GI. Glucose uptake capacity by yeast cells was evaluated in presence of all rice genotypes/lines extract and it was observed that all the varieties except Jaya, Komal and 97 shows increase in % glucose uptake as compared to control sample.  Allelic variations of marker RM190 for the waxy gene have also shown variations for tested rice genotypes/lines. Rice varieties such as inbreed lines 84, 87, 97, 6-5 and 128 which have lower GI are better for diabetes management.