RD91, a Non-glutinous Rice Variety

Abstract

Export markets of Thai rice in many countries have yet demanded a medium grain rice due to severe and long-term drought in new rice producing countries. In Thailand there is only one medium grain rice variety, RD81, which still lacks of some characteristics to satisfy diverse market needs. Therefore, research was conducted to obtain a variety with medium grain (as demanded by export market), high yield, early maturity and photoperiod-insensitive for cultivation in irrigated paddy fields in order to increase opportunity and expand Thai rice markets. Seeds of rice restorer line (R line), IR101870-60-1, were introduced from the International Rice Research Institute and grown for pure line selection from F₅ to F₇, to obtain a medium grain line, IR101870-60-1-PTT-5-3-27. Research have been carried out during 2015 to 2021 through the following crop improvement steps, i.e., varietal observation, yield trials, evaluation on rice disease and insect pests, response to N fertilizer application, analyses for grain physical and chemical quality, milling quality, cooking and eating quality, and evaluation of farmers' acceptance. The promising line was subsequently approved by the Varietal Releasing Committee of the Rice Department to be a certified variety, "RD91". It is a photoperiod-insensitive, non-glutinous rice with 107 days to harvest (transplanting), 107 cm height, erect plant type, green leaf color, moderately well-exserted panicle, 30.7 cm leaf length, mostly compact panicle, 200 fertile seeds per panicle, low panicle shattering and easy panicle thresh ability. RD91 has straw-colored husk, medium grain size with a paddy grain size of 8.25 mm length, 3.10 mm width, 2.06 mm thickness, and white dehulled grain with 5.73 mm length, 2.63 mm width, and 1.86 mm thickness. It has medium grain shape, moderately large chalkiness (1.60), good milling quality (62.2 percent whole kernel and head rice), low gelatinization temperature, soft gel consistency, normal elongation ratio (1.67), and soft, slightly sticky and non-aromatic cooked rice. Remarkable features of RD91 are medium grain size, non-glutinous, photoperiod-insensitive, low amylose content (18.49 percent), leaf blast resistance, high yield (763 kg/rai) with yield potential of 1,100 kg/rai in farmers' fields. It is recommended for irrigated paddy areas in central and lower northern regions, especially where there are demands of entrepreneurs for buying and processing paddy rice yields to milled rice. Caution should be taken as this variety is moderately susceptible or susceptible to brown planthopper and susceptible to bacterial leaf blight.