Hybrid origin and phenotype evolution of the modern maize

The domestication of crops originates from their wild ancestors and typically begins with the selection of phenotypes carrying specific alleles within wild populations. Subsequently, artificial hybridization and the retention of novel mutations introduce new alleles, leading to the continual creation of new phenotypes. The modern maize (Zea mays L.), as one of the most important food crops worldwide, has long attracted significant attention from researchers regarding its domestication and origin. In this review, we have summarized the related advances in clarifying hybrid origin and identifying related genes and allelic origins in maize. Modern maize was initially domesticated from Zea mays ssp. parviglumis approximately 9,000 years ago, followed by hybridization with Z. mays ssp. mexicana around 6,000 years ago, which gave rise to the modern maize lineage. Modern maize, as a hybrid lineage, possesses extensive genetic admixture that serves as the foundation for its phenotypic diversity and wide adaptability to various cultivation environments. Compared to ssp. parviglumis and mexicana, the unique phenotypes of maize were shaped through the selection of allelic combinations from both ancestors and/or the accumulation of novel mutations. Elite alleles from both ancestors hold significant value for biotic and abiotic stress resistance. Identifying these alleles and the underlying molecular mechanisms and incorporating them into modern breeding programs could facilitate the development of new maize germplasm with enhanced adaptability to today's changing environments and improved agricultural productivity.