Abstract
BackgroundIn temperate rice cultivation regions, japonica rice cultivars are grown preferentially because consumers deem them to have good eating quality, whereas indica rice cultivars have high grain yields and strong heat tolerance but are considered to have poor eating quality. To mitigate the effects of global warming on rice production, it is important to develop novel rice cultivars with both desirable eating quality and resilience to high temperatures. Eating quality and agronomic traits were evaluated in a reciprocal set of chromosome segment substitution lines derived from crosses between a japonica rice cultivar ‘Koshihikari’ and an indica rice cultivar ‘Takanari’.ResultsWe detected 112 QTLs for amylose and protein contents, whiteness, stickiness, hardness and eating quality of cooked rice grains. Almost of ‘Koshihikari’ chromosome segments consistently improved eating quality. Among detected QTLs, six QTLs on chromosomes 1–5 and 11 were detected that increased whiteness and stickiness of cooked grains or decreased their hardness for 3 years. The QTLs on chromosomes 2–4 were not associated with differences in amylose or protein contents. QTLs on chromosomes 1–5 did not coincide with QTLs for agronomic traits such as heading date, culm length, panicle length, spikelet fertility and grain yield. Genetic effects of the detected QTLs were confirmed in substitution lines carrying chromosome segments from five other indica cultivars in the ‘Koshihikari’ genetic background.ConclusionThe detected QTLs were associated with differences in eating quality between indica and japonica rice cultivars. These QTLs appear to be widely distributed among indica cultivars and to be novel genetic factors for eating quality traits because their chromosome regions differed from those of the GBSSI (Wx) and SSIIa (Alk) genes. The detected QTLs would be very useful for improvement of eating quality of indica rice cultivars in breeding programs.
Highlights
In temperate rice cultivation regions, japonica rice cultivars are grown preferentially because consumers deem them to have good eating quality, whereas indica rice cultivars have high grain yields and strong heat tolerance but are considered to have poor eating quality
To detect Quantitative trait locus (QTL) involved in the control of eating-quality traits, we used a reciprocal set of Chromosome segment substitution line (CSSL) derived from crosses between a japonica rice cultivar ‘Koshihikari’ and an indica rice cultivar ‘Takanari’ (Takai et al 2014)
Confirmation of the Effects of QTLs in CSSLs of Other indica Cultivars To investigate whether the six detected QTLs would be commonly detected in segregating populations derived from crosses between japonica and other indica rice cultivars, we developed additional CSSLs carrying chromosome segments introduced from indica cultivars ‘Naba’, (2021) 14:8
Summary
In temperate rice cultivation regions, japonica rice cultivars are grown preferentially because consumers deem them to have good eating quality, whereas indica rice cultivars have high grain yields and strong heat tolerance but are considered to have poor eating quality. Eating quality and agronomic traits were evaluated in a reciprocal set of chromosome segment substitution lines derived from crosses between a japonica rice cultivar ‘Koshihikari’ and an indica rice cultivar ‘Takanari’. Rice (Oryza sativa L.) is a staple food for nearly half of the world population (GriSP (Global Rice Science Partnership), 2013). This species is divided into two main subspecies, indica and japonica, which differ in their morphological and physiological characteristics (Khush 1997). In modern rice breeding, programs for indica-background breeding and for japonicabackground breeding are separate, breeders use common agronomically important genes for disease resistance, plant height and stress tolerance in these programs
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