Genomic elucidation of hybridization between Liberica and excelsa coffee and its implications for coffee crop development.

The development and establishment of a broader range of coffee species and hybrids is likely to play a key role in coffee farming sustainability in an era of accelerated climate change. We investigated hybridization between Coffea liberica (Liberica) and C. dewevrei (excelsa) utilizing 7,618 SNPs from 113 accessions, sampled across three continents. Our analyses demonstrated that these two species have hybridized readily in cultivation and produced fertile progeny with a wide range of genomic admixture. We revealed extensive genomic admixture in farmed accessions from Sarawak. The identified hybrids exhibited intermediate characteristics and overlapping values for key agronomic traits, including seed size and parchment thickness. These traits, which influence yield,  outturn and post-harvest processing, can be transferred via hybridization. The hybrids also have the potential to broaden the climate envelope for successful coffee cultivation and transfer disease resistance. Improved genotypes resulting from hybrids between C. liberica and C. dewevrei could be brought into production relatively quickly, as a means of developing both species. We propose the formal name Coffea × libex for the interspecies hybrid.