Sugar beet reference transcriptome generated from a pooled RNA sample containing equivalent amounts of RNA from young, newly developed leaf tissue, fully expanded leaf tissue, root tissue 5 weeks after planting, root tissue 16 weeks after planting, root tissue after 60 days postharvest storage, root tissue 2 days after jasmonic acid (10 uM) treatment, and root tissue 2 days after salicylic acid (1 mM) treatment