Perspectives on the genomics research of important crops in the tribe Andropogoneae: Focusing on the Saccharum complex

Climate changes are shifting the perception of C4 photosynthetic crops due to their superior adaptability to harsh conditions. The tribe Andropogoneae includes some economically important grasses, such as Zea mays, Sorghum bicolor, Miscanthus spp., and Saccharum spp., representing C4 photosynthetic grasses. Although the Andropogoneae grasses diverged fairly recently, their genomic structures are remarkably different from each other. As previously reported, the family Poaceae shares the pan-cereal duplication event occurring ca. 65 MYA. Since this event, Sorghum bicolor has never experienced any additional duplication event. However, some lineage-specific duplication events were reported in Z. mays and Saccharum spp., and, more recently, it was revealed that a shared allotetraploidization event occurred before the divergence between Miscanthus and Saccharum (but after the divergence from S. bicolor), which provided important clues to those two species having large genome sizes with complicated ploidy numbers. The complex genomic structures of sugarcane and Miscanthus (defined as the Saccharum complex along with some other taxa) have had a limiting effect on the use of their molecular information in breeding programs. For the last decade, genomics-associated technologies have become an important tool for molecular crop breeding (genomics-assisted breeding, GAB), but it has not been directly applied to sugarcane and Miscanthus due to their complicated genome structures. As genomics research advances, molecular breeding of those crops can take advantage of technical improvements at a reasonable cost through comparative genomic approaches. Active genomic research of non-model species using closely related model species will facilitate the improvement of those crops in the future.