Abstract
Chinese cabbage (Brassica rapa L. ssp. pekinensis) is one of the most widely cultivated and economically important vegetables in China. Constructing an effective genetic linkage map and mapping quantitative trait loci (QTLs) related to yield and leafy head morphology is of great importance for molecular breeding of Chinese cabbage. Using two diverse Chinese cabbage inbred lines, ZHB and G291, as parents, an F2 segregating population consisting of 240 individuals was prepared for genetic map construction and phenotype investigation in this study. The two parents are significantly different in both shape and size. Sixteen important agronomic traits of F2 individuals were investigated. A genetic map of 105 intragenic simple sequence repeat (SSR) markers distributed across 10 linkage groups (LGs) was constructed, which was 2034.1 cM in length and had an average inter-locus distance of 21.75 cM. We identified 48 QTLs for the tested important agronomic traits on the studied LGs, with LOD scores of 2.51–12.49, which explained the phenotypic variance of 3.41–26.66%. The QTLs identified in this study will facilitate further genetic analysis and marker-assisted genetic improvement of Chinese cabbage.
Highlights
A total of 500 intragenic simple sequence repeat (SSR) markers, distributed across 10 chromosomes of the Brassica rapa A genome (50 markers per chromosome), were randomly selected for polymorphic survey between the parental lines from the SSRs developed by Shi et al (2014) and
The polymorphic SSRs were screened on these 240 F2 individuals, and the results showed that 98 markers (93.33%) had the expected 1:2:1 segregation for the parental alleles (p < 0.01), while seven markers (6.67%) were distorted from the expected segregation ratio
Coefficient of Variation (CV) was used to evaluate the genetic variation of the traits in these 240 F2 lines, and the results showed that head weight, stem length, and gross weight had wider variations than the other traits, with a CV
Summary
Constructing an effective genetic linkage map and mapping quantitative trait loci (QTLs) related to yield and leafy head morphology is of great importance for molecular breeding of Chinese cabbage. After hundreds of years of evolution and breeding, the important agronomic traits related to yield vary greatly among different Chinese cabbage varieties. The inheritance of these yield-related agronomic traits is of great importance for genetic improvement of Chinese cabbage. Most of these traits are complex quantitative traits, and the expression of the controlling genes is influenced by the internal and/or external environment [1,2].
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