Analysis of the Genetic Diversity of <scp><i>Houttuynia cordata</i></scp> Thunb Germplasm and Associated Variations in Lead Content

<i>Houttuynia cordata</i> is an important medicinal and vegetable crop in Southwest China. Due to the accumulation of heavy metal ions such as lead ions (Pb²⁺) in <i>H. cordata</i>, consumption of this plant carries risks, such as ingestion of lead-contaminated <i>H. cordata</i>, may lead to Pb²⁺ bioaccumulation, which is associated with developmental retardation, endocrine disruption, and impairments to immune and neurological functions. In order to screen <i>H. cordata</i> germplasm for low Pb²⁺ absorption and identify the Pb²⁺ adsorption-related agronomic traits and molecular markers, the genetic diversity of a germplasm resource of <i>H. cordata</i> comprising collected 72 accessions was comprehensively evaluated based on agronomic traits and Pb²⁺ contents in the underground stems of the plant. Further, intersimple sequence repeats (ISSR) markers and generalized linear model (GLM) correlation analyses were performed to identify the ISSR loci related to the Pb²⁺ absorption. Ward clustering analysis grouped the 72 accessions of <i>H. cordata</i> into five major classes through analysis of morphological traits. Combined analysis of the Pb²⁺ contents of underground stems with the phenotypic traits revealed significant changes in members within the five classes, indicating that the Pb²⁺ content significantly affected the results of the evaluation of agronomic traits. Greyscale analysis and subsequent verification revealed that the underground stem thickness was closely related to the Pb²⁺ absorption. Based on ISSR markers and subsequent verification, two loci, namely, Locus 21 and Locus 29, were found to have better screening effects on germplasms with low Pb²⁺ adsorption. The accessions that did not carry these two loci in the genome generally exhibited low lead ion adsorption. This study presents a faster marker-based screening for <i>H. cordata</i> plants that are safer for consumption.