Fragrant rice is high in quality and hence its price. The quality of fragrant rice depends on many factors such as variety, region in which it is cultivated, handling practices , etc. Nowadays, consumers{u2019} dema nd for fragran t rice is increasing. However, yield of aromatic rice has been increasing very slowly due to limited cultivat ed areas and is often hampered by infertile and drought - stricken sandy soil. Th is has lead to undesirable trading manipulations such as sale of fake varieties . These include mixing f ragrant rice with non - fragrant and low grade rice and the addition of substances providing fragrant nature. The polymerase chain reaction (PCR) offers possibilities of verification of the rice quality. In t his study, two specific primer pairs, including external sense primer, external antisense primer, internal non - fragrant sense primer and internal fragrant antisense primer were used to differentiate fragrant and non - fragrant rice based on the detection of 8 bp deletion in betaine aldehyde dehydrogenase 2 gene. The method developed helped rapid detection of the purity of the fragrant rice together with conventional PCR method even at 1% and 2% level of adulteration with homogeneous and heterogeneous non - frag rant rice varieties , respectively using only one primer pair, internal non - fragrant sense primer and external antisense primer. The primer pair was also used for quantification of the exact ratio of non - fragrant rice in the sample by real time PCR. Six par ticular fragrant rice varieties were identified using specific RM 1 microsatellite markers . The sensitivity of the method is very strong (less than 1%). The quality evaluation procedure satisfies the requirements of the standard of Thailand Ministry of Com mercial Regulation on Fragrant Rice, which limits the non - fragrant rice content of prime fragrant to less than 10 percent. Overall the method developed can be used to determine the quality of fragrant rice to levels of even 1% adulteration.

A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Technical Science in Food Engineering and Bioprocess Technology, School of Environment, Resources and Development

Thesis (Ph.D.) - Asian Institute of Technology, 2010