AUTHOR=Than Kutay Soe  , Kunieda Mai , Sunohara Hidehiko , Inukai Yoshiaki , Reyes Vincent Pamugas , Nishiuchi Shunsaku , Doi Kazuyuki 

TITLE=A Novel Combination of Genes Causing Temperature-Sensitive Hybrid Weakness in Rice

JOURNAL=Frontiers in Plant Science

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2022.908000

DOI=10.3389/fpls.2022.908000

ISSN=1664-462X

ABSTRACT=<p>Reproductive isolation is an obstacle for plant breeding when a distant cross is demanded. It can be divided into two main types based on different growth stages: prezygotic isolation and postzygotic isolation. The hybrid weakness, which is a type of postzygotic isolation, can become a problem in crop breeding. In order to overcome reproductive isolation, it is necessary to elucidate its mechanism. In this study, genetic analysis for low temperature-dependent hybrid weakness was conducted in a rice F<sub>2</sub> population derived from Taichung 65 (T65, Japonica) and Lijiangxintuanheigu (LTH, Japonica). The weak and severe weak plants in F<sub>2</sub> showed shorter culm length, late heading, reduced panicle number, decreased grain numbers per panicle, and impaired root development in the field. Our result also showed that hybrid weakness was affected by temperature. It was observed that 24°C enhanced hybrid weakness, whereas 34°C showed recovery from hybrid weakness. In terms of the morphology of embryos, no difference was observed. Therefore, hybrid weakness affects postembryonic development and is independent of embryogenesis. The genotypes of 126 F<sub>2</sub> plants were determined through genotyping-by-sequencing and a linkage map consisting of 862 single nucleotide polymorphism markers was obtained. Two major quantitative trait loci (QTLs) were detected on chromosomes 1 [<italic>hybrid weakness j 1</italic> (<italic>hwj1</italic>)] and 11 [<italic>hybrid weakness j 2</italic> (<italic>hwj2</italic>)]. Further genotyping indicated that the hybrid weakness was due to an incompatible interaction between the T65 allele of <italic>hwj1</italic> and the LTH allele of <italic>hwj2</italic>. A large F<sub>2</sub> populations consisting of 5,722 plants were used for fine mapping of <italic>hwj1</italic> and <italic>hwj2</italic>. The two loci, <italic>hwj1</italic> and <italic>hwj2</italic>, were mapped in regions of 65-kb on chromosome 1 and 145-kb on chromosome 11, respectively. For <italic>hwj1</italic>, the 65-kb region contained 11 predicted genes, while in the <italic>hwj2</italic> region, 22 predicted genes were identified, two of which are disease resistance-related genes. The identified genes along these regions serve as preliminary information on the molecular networks associated with hybrid weakness in rice.</p>