Chalky part differs in chemical composition from translucent part of japonica rice grains as revealed by a notched‐belly mutant with white‐belly

Abstract

BACKGROUNDChalkiness has a deleterious influence on rice appearance and milling quality. We identified a notched‐belly mutant with a high percentage of white‐belly, and thereby developed a novel comparison system that can minimize the influence of genetic background and growing conditions. Using this mutant, we examined the differences in chemical composition between chalky and translucent endosperm, with the aim of exploring relations between occurrence of chalkiness and accumulation of starch, protein and minerals.RESULTSComparisons showed a significant effect of chalkiness on chemical components in the endosperm. In general, occurrence of chalkiness resulted in higher total starch concentration and lower concentrations of the majority of the amino acids measured. Chalkiness also had a positive effect on the concentrations of As, Ba, Cd, Cr, Mn, Na, Sr and V, but was negatively correlated with those of B, Ca, Cu, Fe and Ni. By contrast, no significant chalkiness effect on P, phytic acid‐P, K, Mg or Zn was observed. In addition, substantial influence of the embryo on endosperm composition was detected, with the embryo showing a negative effect on total protein, amino acids such as Arg, His, Leu, Lys, Phe and Tyr, and all the 17 minerals measured, excluding Ca, Cu, P and Sr.CONCLUSIONAn inverse relation between starch and protein as well as amino acids was found with respect to chalkiness occurrence. Phytic acid and its colocalized elements K and Mg were not affected by chalkiness. The embryo exerted a marked influence on chemical components of the endosperm, in particular minerals, suggesting the necessity of examining the role of the embryo in chalkiness formation. © 2016 The Authors. Journal of the Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Detection of chalk in single kernels of long‐grain milled rice using imaging and visible/near‐infrared instruments

“…The selected wavelengths, although they varied across the classification definitions, indicated that the discrimination was partially based on starch, protein, and water adsorption bands. These results are similar to the findings that starch composition and water absorption index differ between chalky and vitreous kernels (Kim, Lee, Kim, & Kim, 2000;Lin et al, 2016;Lisle et al, 2000;Patindol & Wang, 2003). Similarly, the model wavelengths of 1,630 nm for MaxLevel, approximately 1,269 and 1,280 nm for modified GIPSA, and approximately 1,202, 1,280, and 1,631 nm for 10% cutoff corresponded to wavelength absorption bands for protein (Pandiselvam, Thirupathi, Mohan, & Uma, 2015;Shenk et al, 1992;Williams & Norris, 2001).…”

“…The growing environment significantly influences the formation of rice chalk (Qiao et al, 2011;Tashiro & Wardlaw, 1991). The relatively slow progress in breeding for low chalkiness reflects the complexity of the underlying mechanisms for how rice chalk occurs and how rice interacts with the growing environment (Lin et al, 2016;Liu et al, 2010). Fitzgerald and Resurreccion (2009) also showed that rice chalk increased with high temperature.…”

“…While chalk is a visible characteristic, it has been shown that the chemical compositions of translucent and opaque, or chalky, rice kernels are different (Cheng, Zhong, Wang, & Zhang, 2005;Chun, Song, Kim, & Lee, 2009;Lin et al, 2016;Lisle, Martin, & Fitzgerald, 2000). While chalk is a visible characteristic, it has been shown that the chemical compositions of translucent and opaque, or chalky, rice kernels are different (Cheng, Zhong, Wang, & Zhang, 2005;Chun, Song, Kim, & Lee, 2009;Lin et al, 2016;Lisle, Martin, & Fitzgerald, 2000).…”

“…The U.S. long-grain rice industry has recently faced increased grain chalk in its widely grown cultivars, which has created challenges for the United States to compete in domestic and international markets (McClung, 2013). Poorly packed crystalline regions due to an incomplete accumulation of starch and protein have been attributed to rice chalk (Lin et al, 2016), which manifests as an opaque area in either the entire grain or a portion of the grain. Rice chalk is affected by both genetics and the growing environment.…”

“…They reported that from two rice varieties that were studied, the yield of marketable rice was zero for the IR8 variety and about 60% for the IR60 variety, as high-temperature treatments resulted in increased chalk. The relatively slow progress in breeding for low chalkiness reflects the complexity of the underlying mechanisms for how rice chalk occurs and how rice interacts with the growing environment (Lin et al, 2016;Liu et al, 2010).…”