Abstract
Eucommia ulmoides (Tu-chung) is an economically and ecologically important tree species which has attracted worldwide attention due to its application in pharmacology, landscaping, wind sheltering and sand fixation. Molecular marker technologies can elucidate the genetic mechanism and substantially improve the breeding efficiency of E. ulmoides. The current research updated the original linkage map, and quantitative trait loci (QTL) analysis was performed on tree growth traits measured over 10 consecutive years in an E. ulmoides F1 population (“Xiaoye” × “Qinzhong No.1”). In total, 452 polymorphic markers were scored from 365 simple sequence repeat (SSR) primers, with an average of 1.24 polymorphic markers per primer combination. The integrated map was 1913.29 cM (centimorgan) long, covering 94.10% of the estimated genome and with an average marker density of 2.20 cM. A total of 869 markers were mapped into 19 major independent linkage groups. Growth-related traits measured over 10 consecutive years showed a significant correlation, and 89 hypothetical QTLs were forecasted and divided into 27 distinct loci. Three traits for tree height, ground diameter and crown diameter detected 25 QTLs (13 loci), 32 QTLs (17 loci) and 15 QTLs (10 loci), respectively. Based on BLASTX search results in the NCBI database, six candidate genes were obtained. It is important to explore the growth-related genetic mechanism and lay the foundation for the genetic improvement of E. ulmoides at the molecular level.
Highlights
As a relic plant that experienced the third glacial period, Eucommia ulmoides is a dioecious perennial deciduous tree (2n = 34) and the only surviving species of the genus Eucommia (Eucommiaceae) [1,2].Historical documents show that E. ulmoides is naturally distributed in central China, protected by complex terrains [1], and it has been considered highly adaptable to various site conditions
Among the 452 polymorphic simple sequence repeat (SSR) markers, 135 markers were identified as l m × ll markers (1:1 segregation ratio), 173 markers were identified as nn × np markers (1:1 segregation ratio), 144 markers were identified as hk × hk markers (3:1 segregation ratio), and the remaining 22 markers (4.87%) showed segregation distortion (p < 0.05) and were excluded from mapping (Table S2)
The genetic linkage map of E. ulmoides consisted of 19 linkage groups with 869 segregating markers covering 1913.29 cM (Table 1, Figure 1, Figure S1)
Summary
As a relic plant that experienced the third glacial period, Eucommia ulmoides is a dioecious perennial deciduous tree (2n = 34) and the only surviving species of the genus Eucommia (Eucommiaceae) [1,2]. Since its successful introduction into France in 1896, E. ulmoides has been introduced into Korea, Japan, Germany, Russia and the United States [3]. E. ulmoides bark has been used as traditional Chinese medicine for thousands of years [4,5]. Modern studies have revealed that E. ulmoides has medicinal and health effects, such as lowering blood glucose and blood lipid levels and regulating blood pressure [6,7]. The gutta-percha in E. ulmoides leaves, fruits and phloem tissues can be a substitute for rubber, exhibit good resistance to strong temperature and acid-base changes, and is an excellent insulator [8]
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