QTL Mapping and Identification of Candidate Genes for Heat Tolerance at the Flowering Stage in Rice.

Lei Chen,Yinghua Pan,Wei Tao,Guoqing Gao,Ligeng Jiang,Xinghai Yang,Tianfeng Liang,Ronghua Lv,Maoyan Tang,Qiang Wang,Xiaoli Zhang

doi:10.3389/fgene.2020.621871

Abstract

High-temperature stress can cause serious abiotic damage that limits the yield and quality of rice. Heat tolerance (HT) during the flowering stage of rice is a key trait that can guarantee a high and stable yield under heat stress. HT is a complex trait that is regulated by multiple quantitative trait loci (QTLs); however, few underlying genes have been fine mapped and cloned. In this study, the F2:3 population derived from a cross between Huanghuazhan (HHZ), a heat-tolerant cultivar, and 9311, a heat-sensitive variety, was used to map HT QTLs during the flowering stage in rice. A new major QTL, qHTT8, controlling HT was identified on chromosome 8 using the bulked-segregant analysis (BSA)-seq method. The QTL qHTT8 was mapped into the 3,555,000–4,520,000 bp, which had a size of 0.965 Mb. The candidate region of qHTT8 on chromosome 8 contained 65 predicted genes, and 10 putative predicted genes were found to be associated with abiotic stress tolerance. Furthermore, qRT-PCR was performed to analyze the differential expression of these 10 genes between HHZ and 9311 under high temperature conditions. LOC_Os08g07010 and LOC_Os08g07440 were highly induced in HHZ compared with 9311 under heat stress. Orthologous genes of LOC_Os08g07010 and LOC_Os08g07440 in plants played a role in abiotic stress, suggesting that they may be the candidate genes of qHTT8. Generally, the results of this study will prove useful for future efforts to clone qHTT8 and breed heat-tolerant varieties of rice using marker-assisted selection.

Highlights

Rice (Oryza sativa L.) is a major staple food crop for nearly half of the world’s population (Pan et al, 2020)
The F2 : 3 population showed a large degree of segregation and some super-parent lines because of their different genetic background, suggesting that the Heat tolerance (HT) of rice at anthesis was a quantitative trait controlled by multiple QTLs/genes
The extreme expression of HT was selected via phenotypic identification to locate heat-tolerant QTLs at the anthesis of rice using bulked-segregant analysis (BSA) combined with whole-genome resequencing (WGS)

Summary

Introduction

Rice (Oryza sativa L.) is a major staple food crop for nearly half of the world’s population (Pan et al, 2020). As global temperatures have increased in recent years, extreme, high temperatures have led to serious losses in yield, decreases in grain quality and reductions in harvest index, especially during the flowering stage, which has a net negative impact on the normal seed setting of rice (Jagadish et al, 2012). Average global temperatures are expected to increase by 2–3◦C over the 30–50 years (Hatfield and Prueger, 2015). Rice yields are expected to decrease by 10% for every increase in daily maximum and minimum temperature of 1◦C (Welch et al, 2010). The average daily temperature is expected to exceed 35◦C for several consecutive days, which will lead to spikelet sterility and abnormal pollination, seriously reducing. Heat Tolerance in Rice the seed-setting rate (IPCC, 2007). There is an urgent need to breed heat-tolerant rice varieties

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Discussion

Conclusion