Relationship between rice grain amylose and pasting properties for breeding better quality rice varieties

Abstract

One hundred and sixty-seven rice varieties/laudraces from 23 different rice-growing countries were used for studying the relationship between the amylose content (AC %) and paste viscosity parameters (RVU) through Pearson correlation. AC and paste viscosity parameters were measured using Auto Analyser and Rapid Visco Analysers respectively. Based on all five RVA pasting properties, i.e. peak viscosity (PV), minimum viscosity (MV), breakdown (BD), final viscosity (FV) and setback (SB), the simple paired t-test (at P ¼ 0.05) was carried out to identify varieties that showed non-significant differences (similar) from the check variety, separately for each of the four AC groups, e.g. Waxy rice AC (0-8%, n ¼ 21) -ÔIR29Õ (Philippines); Low AC (8.1-16%, n ¼ 58) -ÔKoshihikariÕ (Japan); Intermediate AC (16.1-24%, n ¼ 64) -ÔLocal SadriÕ (Iran); high AC (>24.1%, n ¼ 24) -ÔKasalathÕ (India). Significant variation among the rice varieties for AC and pasting properties were observed. Means of the AC and the viscosity parameters including PV, MV, BD, FV and SB were 15.8, 416.1, 180.3, 235.8, 380.9 and 200.6 RVU respectively. Significant correlations existed between AC and paste viscosity parameters at AC group level. The paste viscosity parameters, i.e. PV, BD and SB are important within an AC group as far as cooking quality is concerned. In the low AC group, ÔKoshihikariÕ (check) was most preferred by Japanese consumers, which was used for identifying 16 varieties that showed non-significant differences for pasting properties with it. Some of the important Japanese varieties were ÔTodorokiwaseÕ, ÔOwarihatamochiÕ, ÔSasanishikiÕ, ÔReimeiÕ and ÔKinuhikariÕ. These varieties had good cooking quality with low AC, high PV and BD with low SB. In contrast, the Iranian cultivar ÔLocal SadriÕ with good cooking quality had intermediate levels of AC and SB while recording high PV and BD. The varietal diversity for pasting properties available within each AC group may allow the breeder to make effective selections for improving the cooking quality according to consumer choice.

Genetic Diversity of Rice Grain Quality

“…On the other hand, the slope from pasting to PV was clearly significantly higher in waxy rice than in non-waxy rice (except for the very low amylose class) when the slope was computed based on temperature; when the slope was computed based on the time, the waxy varieties only had significant difference in slope when compared to the high amylose varieties. The results of these comparisons are in agreement with visual comparisons of viscosity profiles in previous reports (Allahgholipour et al, 2006;Horibata et al, 2004;Yan et al, 2005 …”

“…PV, TV, and FV are the lowest in waxy rice varieties (Figure 4b and Figure 5a-c), consistent with a previous report (Allahgholipour et al, 2006). The low FV in waxy varieties is likely to be explained by the absence of amylose chains.…”

“…Within the starch granule, amylose is believed to surround and to bind amylopectin blocklets together (Gallant et al, 1997;Morris, 2006;Ridout et al, 2006;Tang et al, 2006) which suppresses swelling of non-waxy starch granules (Lii et al, 1996). The effect on the swelling capacity of starch granules predictably affects the viscosity profiles of nonwaxy and waxy starch (Allahgholipour et al, 2006;Fitzgerald et al, 2003); hence, viscosity curves can be used to distinguish waxy from non-waxy rice.…”

Determination of Changes of Amylose and Amylopectin Content of Paddy during Early Storage

“…Since starch is the main constituent in rice, it governs the final texture of cooked rice. Starch characteristics determine the amylose content and gelatinization temperature [5], [6]. Amylose and amylopectin determines the cooking quality of rice.…”

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“…3c shows the viscosity traces of HNN and shows that the final viscosity rises from the trough significantly more than it does for the other varieties, leading to a higher final viscosity. This rise from the trough to the final viscosity is usually associated with firmness of the cooked rice 12 , which is usually associated with amylose content 25,[34][35][36] . Waxy rice does not contain amylose due to a mutation in the Waxy gene 2 , but Fig.…”