Genetic diversity and selection in the maize starch pathway

TLDR

Maize exhibits extensive genetic diversity, yet loci under artificial selection, such as those in starch metabolism, often show reduced variation, highlighting a gap in understanding how selection shapes agronomically important pathways. The study surveyed nucleotide diversity at six major starch‑metabolism genes to assess the impact of selection. The survey revealed unusually low genetic diversity and strong selection signals in these genes, indicating a need to shift breeding strategies toward incorporating alleles from wild relatives.

Abstract

Maize is both phenotypically and genetically diverse. Sequence studies generally confirm the extensive genetic variability in modern maize is consistent with a lack of selection. For more than 6,000 years, Native Americans and modern breeders have exploited the tremendous genetic diversity of maize ( Zea mays ssp. mays ) to create the highest yielding grain crop in the world. Nonetheless, some loci have relatively low levels of genetic variation, particularly loci that have been the target of artificial selection, like c1 and tb1 . However, there is limited information on how selection may affect an agronomically important pathway for any crop. These pathways may retain the signature of artificial selection and may lack genetic variation in contrast to the rest of the genome. To evaluate the impact of selection across an agronomically important pathway, we surveyed nucleotide diversity at six major genes involved in starch metabolism and found unusually low genetic diversity and strong evidence of selection. Low diversity in these critical genes suggests that a paradigm shift may be required for future maize breeding. Rather than relying solely on the diversity within maize or on transgenics, future maize breeding would perhaps benefit from the incorporation of alleles from maize's wild relatives.