Population genetics and genome‐wide association studies provide insights into the influence of selective breeding on genetic variation in lettuce

Genetic diversity is an important resource in crop breeding to improve cultivars with desirable traits. Selective can lead a reduction of genetic diversity. However, our understanding on this subject remains limited lettuce (Lactuca sativa L.). Genotyping-by-sequencing (GBS) provide reduced version the genome as cost-effective method identify variants across genome. We genotyped diverse set 441 accessions using GBS method. Phylogenetic and population analyses indicated substantial divergence among four horticultural types lettuce: butterhead, crisphead, leaf, romaine. Genetic-diversity estimates between within that crisphead type was most differentiated from other types, whereas its homogenous slowest linkage disequilibrium (LD) decay types. These results suggested lettuces had relatively less variation well low gene flow identified putative selective sweep regions showed type. Genome-wide association study (GWAS) quantitative trait loci (QTL) provided evidence these genomic were, part, associated delayed bolting, implicating positive selection bolting reducing variation. Our findings enhance current impacts patterning lettuce.