Abstract
Rhizomes facilitate the wintering and vegetative propagation of many perennial grasses. Sorghum halepense (johnsongrass) is an aggressive perennial grass that relies on a robust rhizome system to persist through winters and reproduce asexually from its rootstock nodes. This study aimed to sequence and assemble expressed transcripts within the johnsongrass rhizome. A de novo transcriptome assembly was generated from a single johnsongrass rhizome meristem tissue sample. A total of 141,176 probable protein‐coding sequences from the assembly were identified and assigned gene ontology terms using Blast2GO. Estimated expression analysis and BLAST results were used to reduce the assembly to 64,447 high‐confidence sequences. The johnsongrass assembly was compared to Sorghum bicolor, a related nonrhizomatous species, along with an assembly of similar rhizome tissue from the perennial grain crop Thinopyrum intermedium. The presence/absence analysis yielded a set of 98 expressed johnsongrass contigs that are likely associated with rhizome development.
Highlights
Rhizomes are the horizontally-aligned subterranean stems which allow a perennial plant to grow back from dormancy after a period of harsh seasonal conditions
The proposed coding sequences have an average length of 825 base pairs and range from 297 to 15,174 bp
An N50 value of 1,071 bp indicates that the contigs of this length or longer make up 50% of the total assembly length in base pairs
Summary
Rhizomes are the horizontally-aligned subterranean stems which allow a perennial plant to grow back from dormancy after a period of harsh seasonal conditions. With rhizomes at sufficient depth, an herbaceous plant may reemerge each year without having to make the extensive investment into root growth required by germination. The growing season for a rhizomatous plant is lengthened when its roots reach below the top layer of the soil, reducing the effects of environmental stresses such as temperature. A large persisting root network allows perennial plants to limit soil erosion, reduce runoff, and store more carbon underground as compared with an annual crop (Cox, Glover, Van Tassel, Cox, & DeHaan, 2006). Annual species such as wheat or corn require frequent disruptions from tillage and can only achieve diminished root depth and length before harvest. The loss of nitrate N through subsurface drainage may be 30 to 50 times greater in annual than in perennial crops (Randall & Mulla, 2001)
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