Co-downregulation of the hydroxycinnamoyl-CoA:shikimate hydroxycinnamoyl transferase and coumarate 3-hydroxylase significantly increases cellulose content in transgenic alfalfa (Medicago sativa L.)

•Co-suppressed the two key enzymes in the lignin biosynthesis pathway—HCT and C3H in alfalfa.•The genetically modified alfalfa exhibits reduced lignin content, increased cellulose content and increased saccharification efficiency.•The genetically modified alfalfa improves the recovery of fermentable sugars from lignocellulosic materials.