ABSTRACT
Comparative analysis of the Kao Dawk Mali 105 (KDML 105) premium rice variety, and its six mutants, obtained after low energy ion bombardment, was carried out for sensory and other consumer acceptance related important properties. Consumer acceptance test (n = 200), colour parameters (L*, a*, b*), grain length, and texture parameters of cooked rice and 2-Acetyl-1-pyrroline (2AP), amylose, fat, and protein contents of polished rice were determined. The consumer acceptance test showed that HyKOS3-1 and KDML 105 were equally accepted for every attribute, while HyKOS16 had lower colour liking than KDML 105. Other mutants of KDML 105 were less accepted than KDML 105. Preference mapping (PCA bi-plot) showed that the overall liking of cooked rice was positively correlated to 2AP and fat content and negatively correlated to hardness, cohesiveness, springiness, chewiness, amylose and protein contents. Consumers preferred cooked rice which has good aroma and soft texture. However, only 2AP content might be not enough to explain aroma liking of cooked rice and rice with different texture could be accepted in the same level of KDML 105.
ABSTRACT
The culm length of two semidwarf rice mutants (PKOS1, HyKOS1) obtained from low-energy N-ion beam bombardments of dehusked Thai jasmine rice (Oryza sativa L. cv. KDML 105) seeds showed 25.7% and 21.5% height reductions and one spindly rice mutant (TKOS4) showed 21.4% increase in comparison with that of the KDML 105 control. A cDNA-RAPD analysis identified differential gene expression in internode tissues of the rice mutants. Two genes identified from the cDNA-RAPD were OsSPY and 14-3-3, possibly associated with stem height variations of the semidwarf and spindly mutants, respectively. The OsSPY gene encoded the SPY protein which is considered to be a negative regulator of gibberellin (GA). On the other hand, the 14-3-3 encoded a signaling protein which can bind and prevent the RSG (repression of shoot growth) protein function as a transcriptional repressor of the kaurene oxidase (KO) gene in the GA biosynthetic pathway. Expression analysis of OsSPY, 14-3-3, RSG, KO, and SLR1 was confirmed in rice internode tissues during the reproductive stage of the plants by semi-quantitative RT-PCR technique. The expression analysis showed a clear increase of the levels of OsSPY transcripts in PKOS1 and HyKOS1 tissue samples compared to that of the KDML 105 and TKOS4 samples at the age of 50-60 days which were at the ages of internode elongation. The 14-3-3 expression had the highest increase in the TKOS4 samples compared to those in KDML 105, PKOS1 and HyKOS1 samples. The expression analysis of RSG and KO showed an increase in TKOS4 samples compared to that of the KDML 105 and that of the two semidwarf mutants. These results indicate that changes of OsSPY and 14-3-3 expression could affect internode elongation and cause the phenotypic changes of semidwarf and spindly rice mutants, respectively.
