Variation Pattern and Genome-Wide Association Study of Leaf Phenotypic Traits among Ancient Ginkgo biloba L. Populations

Abstract

Ginkgo biloba L., as one of the oldest tree species, is a very important medicinal plant due to the metabolites in its leaves. To explore the variations and genetic regulation of leaf phenotypic traits, 321 samples from 12 ancient populations in the major distribution areas in China were collected for the leaf morphometric analysis, and 126 samples from 9 ancient populations were used for the genome-wide association study (GWAS) of leaf traits. The results showed that the leaf weight (fresh weight and dry weight) and size (areas) varied greatly, while the length:width ratio (LWR) was stable. There were significant differences in leaf traits among different ancient populations (p < 0.01), and population ZJ from eastern China—with a greater leaf weight and size—was ideal for leaf production. Leaf thickness (LT) showed correlations with altitude, longitude and frost-free period, while LWR had a correlation with altitude (p < 0.05). However, the correlations between environmental factors and leaf traits were weak, which may be related to the origin of populations and human activities. A GWAS revealed that 29 single nucleotide polymorphism (SNP) loci and 112 candidate genes related to leaf traits, and Gb_04106, which is related to auxin, may be involved in the genetic regulation of LT. It is speculated that environmental factors may induce leaf morphology of G. biloba by affecting the accumulation of secondary metabolites. The results of this study may provide a theoretical basis for studying the variation pattern and genetic regulation of leaf phenotypes.