Experimental evolution in maize with replicated divergent selection identifies plant-height associated SNPs

Abstract

Experimental evolution studies are common in agricultural research, where they are often deemed "long term selection". These are often used to perform selection mapping, which involves identifying markers which were putatively under selection based on finding signals of selection left in the genome. A challenge of previous selection mapping studies, especially in agricultural research, has been the specification of robust significance thresholds. This is in large part because long term selection studies in crops have rarely included replication. Usually, significance thresholds in long term selection experiments are based on outliers from an empirical distribution. This approach is prone to missing true positives or including false positives. Under laboratory conditions with model species, replicated selection has been shown to be a powerful tool, especially for the specification of significance thresholds. Another challenge is that commonly used single-marker based statistics may identify neutral linked loci which have hitchhiked along with regions that are actually under selection. In this study, we conducted divergent, replicated selection for short and tall plant-height in a random mating maize population under real field conditions. Selection of the 5% tallest and shortest plants was conducted for three generations. Significance thresholds were specified using the false discovery rate for selection (FDRfS) based on a window-based statistic applied on a statistic leveraging replicated selection (FSTSum). Overall, we found 3 significant regions putatively under selection. One region was located on chromosome 3 close to the plant-height genes Dwarf1 and iAA8. We applied a haplotype block analysis to further dissect the pattern of selection in significant regions of the genome. We observed patterns of strong selection in the subpopulations selected for short plant height on chromosome 3.