Endosperm enzyme activity is responsible for texture and eating quality of cooked rice grains in Japanese cultivars

Abstract

Eating quality of cooked rice grains is an important determinant of its market price and consumer acceptance. To comprehensively assess the variation of eating-quality traits in 152 Japanese rice cultivars, we evaluated activities of eight endosperm enzymes related to degradation of starch and cell-wall polysaccharides. Endosperm enzyme activities showed a wide range of variations and were lower in recently developed cultivars than in landraces and old improved cultivars. Activities of most endosperm enzymes correlated significantly with the eating-quality score and surface texture of cooked rice grains. Principal component analysis revealed that rice cultivars with high eating-quality scores had high stickiness of the grain surface and low levels of endosperm enzyme activities. These results suggest that endosperm enzyme activities control texture and eating quality of cooked rice grains in Japanese rice cultivars.

Genomic Regions Involved in Differences in Eating and Cooking Quality Other than Wx and Alk Genes between indica and japonica Rice Cultivars

“…Many studies have reported QTLs for eating quality and starch characteristics corresponding to the Wx and Alk genes in mapping populations derived from crosses between indica and japonica rice cultivars (Tan et al 1999;Wan et al 2004;Tian et al 2005;Takeuchi et al 2007;Su et al 2011;Yang et al 2018;Yang et al 2020). The 'Takanari' allele of the Wx gene is identical with the japonica-type Wx b allele, and the amylose content is not much different from that of 'Koshihikari' (Aoki et al 2015;Hori et al 2016;Iijima et al 2019). In this study, we did not also detect any QTLs in the chromosome region of the Alk gene, which also greatly affects starch properties.…”

“…Positive additive effect means 'Takanari' allele increasing the trait values et al 2014; Hori et al 2016;Iijima et al 2019). Generally, cooked grains of japonica cultivars are more sticky and softer than those of indica cultivars (Hori and Yano 2013).…”

“…Eating quality traits were evaluated by instrumental methods according to Hori et al (2016) and Iijima et al (2019). Apparent amylose content was determined by using an Auto Analyzer II (Bran+Luebbe Co. Ltd., Norderstedt, Germany).…”

“…Eating quality traits are easily affected by many agronomic traits including heading date, grain size and weight, grain number per panicle and spikelet fertility (Juliano et al 1993;Iijima et al 2019). We evaluated agronomic traits of the CSSLs, in particular those of the six CSSLs each carrying a QTL on chromosomes 1-5 and 11.…”

“…Amylose and protein contents of a Japanese indica cultivar 'Takanari' are not much different from those of the japonica cultivar 'Koshihikari', which is a leading cultivar in Japan (Hori et al 2016;Iijima et al 2019). However, 'Takanari' has the Wx b allele introduced from japonica cultivars (Aoki et al 2015).…”