Oligo-carrageenans induce a long-term and broad-range protection against pathogens in tobacco plants (var. Xanthi)

Here, we analyzed the effect of oligo-carrageenans kappa, lambda and iota on protection against tobacco mosaic virus (TMV), Botrytis cinerea Whetzel and Pectobacterium carotovorum Waldee and suppression of infections in tobacco plants. Treatment with increasing concentrations of oligo-carrageenans, increasing number of treatments and increasing time after treatment enhanced protection against TMV indicating a long-term protection that mimics vaccination, mainly oligo-carrageenan lambda. In addition, oligo-carrageenans induced protection against P. carotovorum with similar efficiencies and against B. cinerea, mainly oligo-carrageenans lambda and iota. Moreover, oligo-carrageenans induced a partial suppression of TMV and P. carotovorum infections and a complete suppression of B. cinerea infection at systemic level. Furthermore, oligo-carrageenans induced a sustained activation of phenylalanine ammonia lyase activity and the accumulation of phenylpropanoid compounds with potential antimicrobial activities suggesting these compounds are involved in protection and suppression effects.

► Oligo-carrageenans induced protection against viral, fungal and bacterial infections.
► Oligo-carrageenans induced suppression of viral, fungal and bacterial infections.
► Oligo-carrageenans increased PAL activity and the accumulation of phenylpropanoids.