A walk on the wild side: Oryza species as source for rice abiotic stress tolerance

Abstract

Oryza sativa, the common cultivated rice, is one of the most important crops for human consumption, but production is increasingly threatened by abiotic stresses. Although many efforts have resulted in breeding rice cultivars that are relatively tolerant to their local environments, climate changes and population increase are expected to soon call for new, fast generation of stress tolerant rice germplasm, and current within-species rice diversity might not be enough to overcome such needs. The Oryza genus contains other 23 wild species, with only Oryza glaberrima being also domesticated. Rice domestication was performed with a narrow genetic diversity, and the other Oryza species are a virtually untapped genetic resource for rice stress tolerance improvement. Here we review the origin of domesticated Oryza sativa from wild progenitors, the ecological and genomic diversity of the Oryza genus, and the stress tolerance variation observed for wild Oryza species, including the genetic basis underlying the tolerance mechanisms found. The summary provided here is important to indicate how we should move forward to unlock the full potential of these germplasms for rice improvement.

Figure 1. Submergence tolerance and genetic architecture of SUB1 locus in cultivated and wild Oryza species. Genotypes from AA genome species Oryza sativa, Oryza rufipogon and Oryza nivara are tolerant or sensitive to submergence depending on the presence of SUB1A-1 allele of the SUB1A gene. Genotypes that either have SUB1A-2 allele or lack a SUB1A, carrying only SUB1B and SUB1C genes, are sensitive. Genotypes from CC genome species Oryza eichingeri, Oryza rhizomatis and the CCDD tetraploid species Oryza grandiglumis were shown to be tolerant to submergence while carrying a SUB1A gene-lacking SUB1 locus, indicating the locus does not contribute to the stress tolerance in these species.