The Next Generation of Rice: Inter-Subspecific Indica-Japonica Hybrid Rice

Abstract

Rice (Oryza sativa) is an important food crop and has two subspecies, indica and japonica. Since the last century, four generations of rice varieties have been applied to rice production. Semi-dwarf rice, intra-subspecific hybrid rice, and inter-subspecific introgression rice were developed successively by genetic modification based on the first generation of tall rice. Each generation of rice has greater yield potential than the previous generation. Due to the stronger heterosis of indica-japonica hybrids, utilization of the inter-subspecific heterosis has long been of interest. However, indica-japonica hybrid sterility hinders the utilization of heterosis. In the past decades, indica-japonica hybrid sterility has been well understood. It is found that indica-japonica hybrid sterility is mainly controlled by six loci, S5, Sa, Sb, Sc, Sd, and Se. The indica-japonica hybrid sterility can be overcome by developing indica-compatible japonica lines (ICJLs) or wide-compatible indica lines (WCILs) using genes at the loci. With the understanding of the genetic and molecular basis of indica-japonica hybrid sterility and the development of molecular breeding technology, the development of indica-japonica hybrid rice has become possible. Recently, great progress has been made in breeding indica-japonica hybrid rice. Therefore, the indica-japonica hybrid rice will be the next generation of rice. It is expected that the indica-japonica hybrid rice will be widely applied in rice production in the near future.

Reconstruction of the High Stigma Exsertion Rate Trait in Rice by Pyramiding Multiple QTLs

“…In the past decades, great progress has been made in the heterosis utilization of hybrid rice (Yuan, 2017 ; Zhang, 2022 ). Improving the outcrossing ability of MSLs is very important for hybrid rice seed production.…”

“…Since then, hybrid rice has been widely planted in China and around the world (Yuan and Virmani, 1988 ). The hybrid rice exhibits strong heterosis, which plays an important role in improving rice yield (Cheng et al, 2007 ; Zhang et al, 2021 ; Zhang, 2022 ). Since male sterility lines (MSLs) are used to produce hybrid seeds by outcrossing with restorer lines of male parents, the outcrossing ability of MSLs is a key factor in improving hybrid seed yield.…”

Non-coding RNA expression analysis revealed the molecular mechanism of flag leaf heterosis in inter-subspecific hybrid rice

“…The molecular mechanism of heterosis is still unclear through extensive studies on genome, transcriptome and epigenetics ( Larièpe et al, 2012 ; Shen et al, 2014 ; Shao et al, 2019 ; Wang and Wang, 2022 ; Zhang, 2022 ). In recent years, several ncRNAs and their corresponding regulatory networks have been proved to play important roles in plant growth and development ( Ohtani, 2017 ; Yuan et al, 2018 ; Luan et al, 2019 ; Wang et al, 2020 ; Zhai et al, 2020 ; Chand Jha et al, 2021 ; Qiao et al, 2021 ).…”

“…However, there are few studies on the role of ncRNA in plant heterosis so far, which have been conducted in maize and cabbage ( Crisp et al, 2020 ; Hou et al, 2020 ; Li et al, 2021 ). As a hybrid rice with high yield potential, indica × japonica hybrid rice has always been an important material for heterosis research ( Xiong et al, 2021 ; Zhang, 2022 ). This study demonstrated that ncRNA plays an important role in the heterosis of inter-subspecific hybrid rice by comprehensively analyzing the expression profile of ncRNA and the ncRNA regulatory network related to heterosis.…”

“…japonica Kato), have different physiological traits, genomic and epigenetic differentiation ( Liu et al, 2007 ; Lu et al, 2022 ). These differences lead to obvious heterosis in inter-subspecific hybrid rice, which has potential production and research value ( Zhang, 2022 ).…”