Gamma rays induced mutation for low phytic acid and trypsin inhibitor content in soybean

Soybean (Glycine max (L.) Merrill) is an important source of vegetable protein and is used as a food, feed and health supplement. However, consumption of soybean as food is limited because of the presence of many anti-nutritional factors. Trypsin inhibitors and phytic acid are two major anti-nutritional factors present in soybean that need to be removed for increasing the soybean consumption as food. Trypsin inhibitor is known to inhibit the trypsin/chymotrpsin activity and phytic acid reduces the bioavailability of essential micronutrients in digestive tract, resulting in adverse effect on health. Therefore, developing soybean cultivars having low trypsin inhibitors and phytic acid content is highly desirable. Soybean cultivar JS 93-05 was irradiated with 250 Gy gamma rays to induce mutation for various morphological and biochemical characters. A large number of mutants with altered morphological characters were identified. Ninety true breeding mutant lines in M6 generation were screened for trypsin inhibitor and phytic acid content. The phytic acid content was estimated using modified colorimetric method and trypsin inhibitor concentration was estimated using BAPNA as substrate in colorimetric method. The phytic acid content in the mutants varied from 7.59 to 24.14 mg g^-1 . Two mutants lines TSG - 62 (7.59 mg g^-1) and TSG - 66 (9.62 mg g^-1) showed significant low phytic acid content as compared to the parent JS 93-05 (20.19 mg g^-1). The trypsin inhibitor concentration in the mutants varied from 19.92 to 53.64 TIU mg^-1 and one mutant line (TSG -14) was found with the lowest trypsin inhibitor concentration of 19.92 TIU mg^-1 compared to parent JS 93-05 (50.90 TIU mg^-1). The mutant lines identified in this study will serve as important genetic resources for developing low phytic acid and low trypsin inhibitor cultivars in soybean. (author)