Fine Mapping of qWCR4, a Rice Chalkiness QTL Affecting Yield and Quality

Huan Shi,Xianghua Li,Peng Yun,Guangming Lou,Yuqing He,Yipei Wang,Guanjun Gao,Yun Zhu,Qinglu Zhang,Lu Wang

doi:10.3390/agronomy12030706

Huan Shi, Xianghua Li + Show 8 more

Open Access

https://doi.org/10.3390/agronomy12030706

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Abstract

Rice (Oryza sativa L.) chalkiness greatly reduces the rice quality and the commercial value. In this study, qWCR4, a previously reported quantitative trait locus (QTL) of white-core rate (WCR), was confirmed by a BC5F2 segregation population and further fine mapped to a 35.26 kb region. In the qWCR4 region, LOC_Os04g50060 and LOC_Os04g50070 showed significant differences in expression level in endosperm between two NILs, whereas four other genes had no expression. Starch granules in the central endosperm of chalky grains from NIL(J23B) with higher WCR exhibited a typically round and loosely packed morphology. NIL(J23B) with higher WCR accompanied a higher seed filling speed. Moreover, qWCR4J23B (qWCR4 allele in J23B) increased WCR, grain numbers per plant, seed setting rate, grain width, and thousand-grain weight, contributing to a superior yield per plant. All in all, our research results not only lay a foundation for map-based cloning of qWCR4 but also provide new genetic resources for rice yield and quality breeding.

Highlights

Rice (Oryza sativa L.) is a primary food crop that has greatly contributed to solving the world food security crisis
To validate the genetic effect of qWCR4, a BC5F1 plant that carried a heterozygous qWCR4 region was self-pollinated to obtain the BC5F2 population defined as the near-isogenic lines (NILs)-F2 population
We investigated the starch granules morphology in the endosperm center between two homologous NILs

Summary

Introduction

Rice (Oryza sativa L.) is a primary food crop that has greatly contributed to solving the world food security crisis. More and more attention has focused on the quality of rice concerning the improvement of people’s living standards. As an extremely unsatisfactory quality trait in rice sales and consumption, affects grain appearance and has negative effects on rice processing and cooking characteristics [2]. The chalkiness of rice is characterized by the opaque part of the grain, which can be divided into white-belly (ventral side), white-core (center), and white-back (dorsal side) according to the opaque position [3]. Many studies have shown that chalkiness affects heading yield and milling yield by increasing the incidence of grain breakage [4,5,8]. The chalky grains exhibited lower protein content, and the palatability of cooked rice showed a linear decrease with increasing chalky rice proportion in the sensory evaluation [6]. Reducing the chalkiness rate has become one of the important goals in high-quality rice breeding

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