Abstract
Occurrence of chalkiness in rice is attributed to genetic and environmental factors, especially high temperature (HT). The HT induces heat stress, which in turn compromises many grain qualities, especially transparency. Chalkiness in rice is commonly studied together with other quality traits such as amylose content, gel consistency, and protein storage. In addition to the fundamental QTLs, some other QTLs have been identified which accelerate chalkiness occurrence under HT condition. In this review, some of the relatively stable chalkiness, amylose content, and gel consistency related QTLs have been presented well. Genetically, HT effect on chalkiness is explained by the location of certain chalkiness gene in the vicinity of high-temperature-responsive genes. With regard to stable QTL distribution and availability of potential material resources, there is still feasibility to find out novel stable QTLs related to chalkiness under HT condition. A better understanding of those achievements is essential to develop new rice varieties with a reduced chalky grain percentage. Therefore, we propose the pyramiding of relatively stable and nonallelic QTLs controlling low chalkiness endosperm into adaptable rice varieties as pragmatic approach to mitigate HT effect.
Highlights
Rice (Oryza sativa L.) is an important cereal crop worldwide
Several genetic and environmental factors were shown to influence rice grain appearance, which is usually evaluated as percentage of grains with chalkiness (PGWC) [7]
Yamakawa et al [26] indicated that high temperature impairs grain filling by inhibiting the deposition of storage materials such as starch and protein in rice
Summary
Rice (Oryza sativa L.) is an important cereal crop worldwide. It is the staple food for more than half of the world’s population [1]. Rice grain quality is a complex characteristic including many components such as appearance, cooking qualities, and eating qualities. Chalkiness is reported to occur under the complex genetic network regulation [8] and under the effects of environmental factors, especially heat stress [9, 10]. The genetic basis of appearance quality traits is explained by many QTLs with various effects in different environments [15]. Heat stress was identified as a major inducible factor of chalkiness formation in rice. Genetic approach towards offering a solution for reducing stress effect is illustrated in Perspectives: Pyramiding of Nonallelic Stable QTLs Controlling Low Chalkiness Formation under HT Condition in Rice
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