Abstract
•Analysis of lignin content in brittle leaf disease affected date palm leaves and roots showed less lignin content in affected leaves.•Lignin histochemical analysis of leaves and roots revealed hypo-lignification of leaves and hyper-lignification in affected roots.•Genome-wide analysis and phylogenetic analysis of CCR and CAD families in date palm.•Expression analysis of CCR and CAD genes in healthy control and affected leaves, roots and offshoots.
Brittle leaf disease or Maladie de la Feuille Cassante (MFC) is a lethal disorder of date palm that has assumed epidemic proportions in the oases of Tunisia and Algeria. No pathogen could ever be associated with the disease, while leaflets of affected palms have been previously shown to be deficient in manganese. The work reported here aims to understand the biochemical basis of the date palm response to this disorder. Since the typical disease symptom is the leaf fragility, we have investigated lignin content in leaves and roots. Strong decrease in total lignin content was observed in affected leaves, while lignin content increased in affected roots. Histochemical analyses showed hyperlignification thicker suberin layer in roots cortical cells. The phenylpropanoids pathway was also disrupted in leaves and roots, cinnamoyl-CoA reductase and cinnamyl-alcohol dehydrogenase gene expression was affected by the disease which severely affects the cell wall integrity.