Changes in Cell Wall-bound Phenolic Compounds and Lignin in Roots of Date Palm Cultivars Differing in Susceptibility to Fusarium oxysporum f. sp. albedinis

The roots of date palm contain four cell wall!bound phenolic acids identi_ed as p!hydroxybenzoic\ p!coum! aric\ ferulic and sinapic acids[ The ferulic acid represents the major phenolic compound since it constitutes 37[1 44[7) of cell wall!bound phenolic acids[ All these phe! nolic acids were present in the resistant cultivar "BSTN# and the susceptible cultivar "JHL#[ However\ the pre! infection contents of p!coumaric\ ferulic and sinapic acids were greater in the resistant cultivar than in the sus! ceptible one[ For the contents of p!hydroxybenzoic acidthere was no signi_cant di}erence between the resistant cultivar and the susceptible cultivar[ Similarly\ the pre! infection contents of lignin were approximately equal for both cultivars[ Inoculation of the date palm roots by Fusarium oxysporum f[ sp[ albedinis induced important modi_cations to the contents of the cell wall!bound phe! nolic compounds and lignin\ which made it possible to distinguish between resistant and susceptible cultivars[ The post!infection contents of cell wall!bound phenolic compounds underwent a rapid and intense increase with a maximum accumulation on the tenth day for p!hyd! roxybenzoic acid "0[43 mmol:g#\ p!coumaric acid "1[66 mmol:g# and ferulic acid "1[53 mmol:g# and on the _fteenth day for sinapic acid "0[74 mmol:g#[ The maximum contents accumulated in the resistant cultivar were greater than those in the susceptible cultivarnamely\ 00 times for p!hydroxybenzoic acid\ 1[5 times for p!coumaric acid\ 0[7 times for ferulic acid and 01[2 times for sinapic acid[ In the susceptible cultivar\ p!coumaric acid and ferulic acid contents also increased after inocu! lation although they did not reach the pre!infection con! Present address] INRA\ Centre Re gional du Gharb\ 03 Rue Abou Temmam\ Ke nitra\ Morocco[ U[ S[ Copyright Clearance Center Code Statement] 9820 0674:1999:3796 9394 , 04[99:9 tents of the resistant cultivar[ The contents of p! hydroxybenzoic acid in the susceptible cultivar roots did not present post!infection modi_cation and those of sina! pic acid decreased instead[ The lignin contents increased in both cultivars with a maximum accumulation on the _fteenth day[ However\ the maximum contents accumu! lated in the resistant cultivar roots were 0[4 times greater than those of the susceptible cultivar[ These results showed clear di}erences between the resistant BSTN and the susceptible JHL cultivars[ The implication of cell wall!bound phenolic compounds and lignin in the resist! ance of date palm to F[ oxysporum f[ sp[ albedinis appears to be dependent on the speed and intensity of their accumulation with greater contents in the _rst stage of infection[