Potential approaches to create ultimate genotypes in crops and livestock

Many thousands and, in some cases, millions of individuals from the major crop and livestock species have been genotyped and phenotyped for the purpose of genomic selection. ‘Ultimate genotypes’, in which the marker allele haplotypes with the most favorable effects on a target trait or traits in the population are combined together in silico, can be constructed from these datasets. Ultimate genotypes display up to six times the performance of the current best individuals in the population, as demonstrated for net profit in dairy cattle (incorporating a range of economic traits), yield in wheat and 100-seed weight in chickpea. However, current breeding strategies that aim to assemble ultimate genotypes through conventional crossing take many generations. As a hypothetical thought piece, here, we contemplate three future pathways for rapidly achieving ultimate genotypes: accelerated recombination with gene editing, direct editing of whole-genome haplotype sequences and synthetic biology. This Perspective discusses approaches to generate ultimate genotypes, combining the best chromosome segments in livestock and crop populations, to increase key production, sustainability and welfare traits, compared with the current best individuals.