Interspecific Hybridization Is an Important Driving Force for Origin and Diversification of Asian Cultivated Rice Oryza sativa L.

Abstract

As one of the most important crops, Asian cultivated rice has evolved into a complex group including several subgroups adapting various eco-climate-systems around the globe. Here, we pictured a comprehensive view of its original domestication, divergences, and the origin of different subgroups by integrating agriculture, archeology, genetics, nuclear, and cytoplasm genome results. Then, it was highlighted that interspecific hybridization-introgression has played important role in improving the genetic diversity and adaptation of Oryza sativa during its evolution process. Natural hybridization-introgression led to the origin of indica, aus, and basmatic subgroups, which adapted to changing cultivated environments, and produced feral weedy rice coexisting and competing with cultivars under production management. Artificial interspecific hybridization-introgression gained several breakthroughs in rice breeding, such as developing three-line hybrid rice, new rice for Africa (NERICA), and some important pest and disease resistance genes in rice genetic improvement, contributing to the stable increase of rice production to meet the expanding human population. We proposed a series to exploit the virtues of hybridization-introgression in the genetic improvement of Asian cultivated rice. But some key issues such as reproductive barriers especially hybrid sterility should be investigated further, which are conducive to gene exchange between cultivated rice and its relatives, and even is beneficial to exploiting interspecific hybrid vigor. New technologies help introduce favorable genes from distant wild species to Asian cultivated rice, such as transgenic and genome editing systems. Rising introgression lines in a wider range with multi-donor benefits allele mining, understanding genetic network of rice growth and development, yield formation, and environmental adaptation. Then, integration of new tools and interspecific hybridization can be a future direction to develop more usable breeding populations which can make Asian cultivated rice more resilient to the changing climate and world.

Diversity of Unusual Ribosomal Genes and Ecological Origin of Rice (Oryza spp.)

“…In the diploid species, O. longistaminata, O. officinalis, and O. australiensis from Africa, Asia, and Australia, respectively, three rDNA families RC1, RC2, and RC3 were detected within the same species. As in Quercus, the intra-and interspecific sequence differences within the clades were usually very low, which was explained for the two oak species by ongoing homogenization within, but not between, rDNA families [19]. The same observation is exhibited in rice.…”

“…Following interbreeding between two different species, xenologous rRNA genes from one parent are usually epigenetically silenced because of nucleolar dominance and probably deleted later. Alternatively, xenologous rRNA genes may be also converted to one sequence type [19], or as in Quercus robur and Quercus petraea, parental rDNA families may be even maintained in the nucleus [20].…”

Three QTL from Oryza meridionalis Could Improve Panicle Architecture in Asian Cultivated Rice

“…Narrow genetic basis of Asian cultivated rice results in the yield bottleneck in rice breeding (Tanksley and Mccouch 1997 ). Interspecific hybridization-introgression played important driving roles in rice domestication and diversification (Zhou et al 2022 ). Therefore, enormous effort has been devoted for exploration favorable genes from wild relatives for rice genetic improvement; some QTL responsible for panicle architecture were detected in the past decades (Gaikwad et al 2020 ).…”

A derived weedy rice × ancestral cultivar cross identifies evolutionarily relevant weediness QTLs

“…To date, the loci underlying most weediness traits that led to de‐domestication of cultivated rice and increased competitiveness of weedy rice have not been identified. In the U.S., the BHA group, a major weedy rice population characterized by having blackhull awned grain, has evolved from aus cultivars (Li et al., 2017; Reagon et al., 2010), a geographically constrained rice variety, centred in the Indian subcontinent (Zhou et al., 2022), and highly tolerant to environmental stresses, such as drought and heat (Casartelli et al., 2018; Civáň et al., 2015). A second major U.S. weedy population, known as the SH group, tends to have strawhull awnless grain and has evolved from indica varieties of cultivated rice (Li et al., 2017; Reagon et al., 2010) that are widely geographically distributed in tropical and subtropical regions (Zhou et al., 2022).…”

“…In the U.S., the BHA group, a major weedy rice population characterized by having blackhull awned grain, has evolved from aus cultivars (Li et al., 2017; Reagon et al., 2010), a geographically constrained rice variety, centred in the Indian subcontinent (Zhou et al., 2022), and highly tolerant to environmental stresses, such as drought and heat (Casartelli et al., 2018; Civáň et al., 2015). A second major U.S. weedy population, known as the SH group, tends to have strawhull awnless grain and has evolved from indica varieties of cultivated rice (Li et al., 2017; Reagon et al., 2010) that are widely geographically distributed in tropical and subtropical regions (Zhou et al., 2022). Previously, quantitative trait locus (QTL) mapping in populations derived from crosses between BHA × indica and SH × indica have been used to detect the genetic bases of multiple weediness traits in BHA and SH (Qi et al., 2015; Thurber et al., 2013).…”