The genetic basis of extra-lobed leaves in ivyleaf morning glory (Ipomoea hederacea)

Intraspecific leaf shape variation is common among angiosperms. Ivyleaf morning glory ( Ipomoea hederacea ) has become a useful system for studying the genetics and ecology of leaf shape variation as this species exhibits two leaf shapes: leaves with entire margins, and 3-lobed leaves. It is known that these phenotypes are controlled by a single locus, and differ in their ecophysiology, geographic distribution, ecology, and fitness. However, individuals producing leaves with 1-2 extra lobes have also been observed, but the genetic basis of these phenotypes have not been described. To investigate the genetic basis of extra-lobing, we compared phenotypic distributions of leaf shapes of an F2 generation to Mendelian ratios for a single locus trait, and conducted a bulked segregant analysis to uncover quantitative trait loci. Our results suggest that producing extra-lobed leaves has a complex genetic basis and that there are multiple QTLs underlying this phenotype containing potential candidate genes involved with auxin distribution and leaf development. Whether these extra-lobed phenotypes also differ in terms of their physiology and ecology remains unexplored.