An RNA-Seq Approach to Study Vernalization and the Induction of Flowering in Perennial Ryegrass

Perennial ryegrass (Lolium perenne L.) is the main forage grass species utilized in temperate agricultural regions due to its high digestibility and feed quality. However, the onset of flowering leads to a decrease in forage quality, and feed quality would therefore be enhanced by prolonging vegetative growth. This has led to a research effort to understand the underlying genetic components affecting variation for flowering time in perennial ryegrass, with the long term goal of developing molecular tools to assist breeding programs in developing varieties with enhanced agricultural value. Vernalization is a key factor in the induction of flowering in perennial ryegrass and was the focus of this study. The transcriptome of two genotypes with contrasting vernalization requirements was studied during both primary (vernalization and short day conditions), and secondary induction (higher temperature and long day conditions) using an RNA-Seq approach. This revealed transcripts with expression profiles indicative of a role to play in floral induction. The expression patterns were validated by quantitative RT-PCR and candidate genes were converted to molecular markers. These genes were mapped in an experimental mapping family segregating for the vernalization requirement and were compared to the location of previously identified vernalization QTLs.