Abstract
Due to China’s rapidly increasing population, the total arable land area has dramatically decreased; as a consequence, the competition for farming land allocated for grain and cotton production has become fierce. Therefore, to overcome the existing contradiction between cotton grain and fiber production and the limited farming land, development of early-maturing cultivars is necessary. In this research, a high-density linkage map of upland cotton was constructed using genotyping by sequencing (GBS) to discover single nucleotide polymorphism (SNP) markers associated with early maturity in 170 F2 individuals derived from a cross between LU28 and ZHONG213. The high-density genetic map, which was composed of 3978 SNP markers across the 26 cotton chromosomes, spanned 2480 cM with an average genetic distance of 0.62 cM. Collinearity analysis showed that the genetic map was of high quality and accurate and agreed well with the Gossypium hirsutum reference genome. Based on this high-density linkage map, QTL analysis was performed on cotton early-maturity traits, including FT, FBP, WGP, NFFB, HNFFB and PH. A total 47 QTLs for the six traits were detected; each of these QTLs explained between 2.61% and 32.57% of the observed phenotypic variation. A major region controlling early-maturity traits in Gossypium hirsutum was identified for FT, FBP, WGP, NFFB and HNFFB on chromosome D03. QTL analyses revealed that phenotypic variation explained (PVE) ranged from 10.42% to 32.57%. Two potential candidate genes, Gh_D03G0885 and Gh_D03G0922, were predicted in a stable QTL region and had higher expression levels in the early-maturity variety ZHONG213 than in the late-maturity variety LU28. However, further evidence is required for functional validation. This study could provide useful information for the dissection of early-maturity traits and guide valuable genetic loci for molecular-assisted selection (MAS) in cotton breeding.
Highlights
To better understand the genetic architecture of early-maturity traits in cotton, we present a linkage map generated from 3,978 single nucleotide polymorphism (SNP) that were developed through genotyping by sequencing (GBS)
The characteristics of markers determine the distribution density of a marker on a genetic linkage map, which further affects the accuracy of the quantitative trait locus (QTL)
We employed GBS to identify a major QTL related to early maturity in cotton using an F2 mapping population
Summary
With the limited arable land in China, there has been a competition between grain and cotton fiber production, which limits crop productivity. To address this and to efficiently utilize the limited farming land throughout the crop growing season, development of early-maturity cultivars with high yields and good fiber quality traits, coupled with resistance to major diseases, is needed. Flowering time (FT), the period from the first flower blooming to the first boll opening (FBP), WGP, node of the first fruiting branch (NFFB), HNFFB and plant height (PH) are important early-maturity-related traits of cotton [2,3,4,5].
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