Gene discovery and marker resource development by transcriptome sequencing from a short‐rotation coppice willow, Salix suchowensis

Abstract

Many willow species, especially the short‐rotation coppice willows, are suitable for development into renewable bioenergy crops. In this study, we conducted high‐throughput transcriptome sequencing of a shrub willow, S. suchowensis, to generate expressed sequence tags (ESTs) for gene discovery and molecular marker development. Totally, 136.1 million clean reads were generated from five different tissues of S. suchowensis using Illumina RNA‐seq technology. De novo sequence assembly produced 90 269 unigenes, among which 64 127 unigenes were annotated in one or more of the NR, Swiss‐Prot, GO, COG and KEGG databases. A total of 21 052 simple sequence repeats were identified in the expressed sequence assemblies, and a primer database containing 36 912 EST‐SSR markers were developed for 12 304 SSR loci. Subsequently, 25 primers were randomly selected for experimental test. Among which, 24 primers succeeded in PCR amplification and 21 produced amplicons in expected sizes, suggesting that the sequence assemblies were of high quality. The established sequence database and marker resource are useful for different aspects of genetic studies on Salix spp., and particularly valuable for marker‐assisted breeding of willows.