RD117, a Non-glutinous Rice Variety

Abstract

Khao Dawk Mali 105 is the most popular non-glutinous rice variety grown by farmers in the northeastern region due to its aroma and excellent cooking and eating qualities. However, its yield was only 351 kilograms per rai, and its tall culm is prone to lodging. Moreover, it is not drought-tolerant and is susceptible to blast and bacterial leaf blight diseases. In order to obtain a photoperiod-sensitive, short-culm, drought-tolerant, non-glutinous rice variety with resistance to blast and bacterial leaf blight diseases, with similar cooking and eating qualities to Khao Dawk Mali 105 for growing in rainfed areas in the northeast, the National Center for Genetic Engineering and Biotechnology (BIOTEC) has crossbred the short-culm, drought-tolerant, nonglutinous rice line, IR57514-PMI-5-B-1-2, a female parent, with the non-glutinous rice line, RGDU99016-MAS-77, a hybrid rice line based on the Khao Dawk Mali 105 genetic material, as a male parent. This rice line is resistant to blast and bacterial leaf blight diseases, with good cooking and eating qualities, and was backcrossed with IR57514-PMI-5-B-1-2 for 4 times and the BC4F2 population was selected. Pedigree selection was conducted from BC4F3-BC4F5, followed by the bulk method in BC4F6-BC4F7 at the Rice Gene Discovery Unit. After that, the bulk method was conducted in BC4F8 and followed by pedigree selection in BC4F9 at Chum Phae, and Nong Khai Rice Research Centers, respectively, the outstanding line, RGDU07343-14-10-4-B-CPA-B-NKI-2, was finally obtained. The varietal study and research were conducted from 2007 to 2024 according to the following breeding protocols: yield trials, disease and insect resistance testing, nitrogen fertilizer response, physical seed quality, milling quality, chemical seed quality, cooking and eating quality. The Rice Department’s Variety Board has approved and certified variety as “RD117”, a photoperiod-sensitive, non-glutinous rice variety suitable for planting in the rainy season. The flowering date is around 16th October (transplanting), and the harvesting date is around 18th November, giving the highest yield of 868 kilograms per rai, with an average yield of 653 kilograms per rai, higher than Khao Dawk Mali 105. It has a compact plant type and a stiff culm, approximately 113 centimeters tall. Its panicle is medium compact with a panicle length of 27.9 centimeters, and the panicle neck is short, with 153 filled grains per panicle. The weight of 1,000 grains is 28.1 grams. Its straw-colored husk with brown grooves has an average paddy length of 10.35 millimeters, 2.64 millimeters width, and 2.03 millimeters thickness. Its white, brown rice has an average length of 7.32 millimeters, 2.21 millimeters width, and 1.79 millimeters thickness. It is classified as long-grain, nonglutinous rice with a slender shape (length-to-width ratio of 3.30). It has a low chalkiness (0.18), good milling quality (46.0 percent whole kernel and head rice), low gelatinization temperature, low amylose content (16.1%), soft gel consistency, normal elongation ratio (1.64 times), sticky, soft, slightly fragrant with aroma compound (2AP) content in brown rice of 1.94 ppm. The dormancy period is 6 weeks. RD117 is resistant to leaf blast at the seedling stage and moderately resistant to bacterial leaf blight disease in the northeastern region but susceptible to neck blast disease, brown planthopper, and rice gall midge. Furthermore, it is more tolerant to drought than Khao Dawk Mali 105, suitable for rainfed rice-growing areas in the northeastern, especially drought-affected areas and areas where blast and bacterial leaf blight diseases are prevalent.