Abstract
Hemp (Cannabis sativa L.) is a bast-fiber crop with a great potential in the emerging bio-based economy. Yet, hemp breeding for fiber quality is restricted and that is mainly due to the limited knowledge of the genetic architecture of its fiber quality. A panel of 123 hemp accessions, with large phenotypic variability, was used to study the genetic basis of seven cell wall and bast fiber traits relevant to fiber quality. These traits showed large genetic variance components and high values of broad sense heritability in this hemp panel, as concluded from the phenotypic evaluation across three test locations with contrasting environments. The hemp panel was genotyped using restriction site associated DNA sequencing (RAD-seq). Subsequently, a large set (> 600,000) of selected genome-wide single nucleotide polymorphism (SNP) markers was used for a genome-wide association study (GWAS) approach to get insights into quantitative trait loci (QTLs) controlling fiber quality traits. In absence of a complete hemp genome sequence, identification of QTLs was based on the following characteristics: (i) association level to traits, (ii) fraction of explained trait variance, (iii) collinearity between QTLs, and (iv) detection across different environments. Using this approach, 16 QTLs were identified across locations for different fiber quality traits, including contents of glucose, glucuronic acid, mannose, xylose, lignin, and bast fiber content. Among them, six were found across the three environments. The genetic markers composing the QTLs that are common across locations are valuable tools to develop novel genotypes of hemp with improved fiber quality. Underneath the QTLs, 12 candidate genes were identified which are likely to be involved in the biosynthesis and modification of monosaccharides, polysaccharides, and lignin. These candidate genes were suggested to play an important role in determining fiber quality in hemp. This study provides new insights into the genetic architecture of fiber traits, identifies QTLs and candidate genes that form the basis for molecular breeding for high fiber quality hemp cultivars.
Highlights
Hemp (Cannabis sativa L.) is a bast-fiber crop with a great potential in the emergent bio-based economy
In total 612,452 single nucleotide polymorphism (SNP) were selected as informative markers for the genetic analysis
A cumulative length of ∼503 Mb was covered by the scaffolds, which corresponds to ∼59.7% of the haploid genome sequence of hemp (843 Mb)
Summary
Hemp (Cannabis sativa L.) is a bast-fiber crop with a great potential in the emergent bio-based economy. It is an environmentally friendly crop that fits well into crop rotation scenarios and sustainable agriculture It can be used for bio-remediation purposes of polluted lands (Struik et al, 2000; Amaducci et al, 2008; van den Broeck et al, 2008; Amaducci and Gusovius, 2010). Despite the large interest in hemp, it is a relatively poorly developed crop This is mostly a consequence of the strong decline in hemp production in the last century, when intensive breeding programs drove great improvements and amplified cultivation of major staple crops (Salentijn et al, 2015). Hemp breeding was restricted and to date little is known about the genetic architecture that underlies hemp fiber quality
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